Eric W. Schneeberger, MD

• Cardiothoracic Surgeon
• Atrial Fibrillation Center
• Deaconess Hospital
• Cincinnati, Ohio

When some strains of group A Streptococcus infect adults hiv infection next day purchase zovirax cream with visa, antibody-antigen complexes accumulate in the glomeruli of the kidneys to trigger glomerulonephritis symptoms of recent hiv infection proven zovirax cream 5 gm, inflammation of the glomeruli and nephrons hiv infection stories cheap zovirax cream 5 gm line. Streptococcal acute glomerulonephritis is a progressive and irreversible kidney disease in adults antiviral remedies herpes order 5 gm zovirax cream otc. Facultative or obligate anaerobic bacteria infecting the vaginal lining may cause bacterial vaginosis antiviral remedies herpes buy zovirax cream uk, a noninflammatory condition associated with odiferous vaginal discharge hiv infection with condom use purchase zovirax cream mastercard. Douching reduces the normal population of lactobacilli in the vagina, elevating the pH and allowing pathogenic bacteria to grow. Following changes in vaginal pH or in the normal microbiome, opportunistic Candida albicans (yeast) causes vaginal candidiasis characterized by curdlike vaginal discharge, itching, and burning. Tertiary syphilis is associated with severe complications resulting from inflammation and a hyperimmune response. Untreated patients can experience dementia, blindness, paralysis, heart failure, and syphilitic gummas (swollen lesions on skin or other organs). Congenital syphilis is a disease of a fetus following transmission in the womb of an infected mother. The results may be death, mental retardation, rash, or the malformation of organs. Chlamydia trachomatis is the most common sexually transmitted bacterium; infections are often asymptomatic in women and produce symptoms similar to gonorrhea in men. Chlamydial infection can also cause inflammation of an epididymis (epididymitis), inflammation of a testis (orchitis), eye disease in babies at birth (trachoma), and lymphogranuloma venereum, which is a genital lesion followed by the development of an inflamed lymph node (a bubo). Herpesviruses also spread by nonsexual means, such as during birth or via contact with herpes blisters on the skin-a condition called whitlow. Papillomavirus causes papillomas, or warts, which range in size from barely detectable to a cauliflower-like growth on the genitals called condylomata acuminata. Gonorrhea is caused by Neisseria gonorrhoeae, which adheres to the epithelial cells of mucous membranes, especially in the genital, urinary, and digestive tracts. It can cause painful urination and pus-filled discharge from the penis in men, uterine tube damage or pelvic inflammatory disease in women, and eye damage in newborns infected during birth. When the bacterium travels inside leukocytes throughout the body, other organs are affected. During primary syphilis, a small, hard, extremely infectious chancre (lesion) fills with spirochetes at the site of infection and remains for several weeks. Trichomoniasis is symptomatic in women (an odiferous, yellowish green vaginal discharge and vaginal irritation) but usually asymptomatic in men. Which of the following sequences most accurately describes the passage of sperm through the reproductive tract Which stage of syphilis is characterized by chancres filled with contagious spirochetes Which of the following is the most common of these sexually transmitted diseases in the United States Inflammation of a kidney Inflammation of the prostate Inflammation of the urinary bladder Inflammation of a testis Inflammation of the rectum Frequent, urgent, and painful urination Muscle pain Inflammation of the conjunctiva in newborns Disease spread from animals to humans Rubbery, painfully swollen lesions in bones, nervous tissue, or on the skin K. Cold sores Toxic shock syndrome Genital warts Syphilis Leptospirosis Lymphogranuloma venereum Genital herpes Gonorrhea Yeast infection Fill in the Blanks 1. The majority (70%) of urinary tract infections are caused by the intestinal bacterium. When the normal lactobacilli of the vagina are replaced by Gardnerella vaginalis or Mycoplasma hominis, the resulting infection is called. Three structural virulence factors of a virulent strain of Neisseria gonorrhoeae are, and. Trachoma, the leading cause of nontraumatic blindness in humans worldwide, is caused by the sexually transmitted bacterium. At a small farm, the children regularly played in a pond that was frequented by livestock. The children were unusually ill one year and complained of stomachaches, vomiting, headaches, and fever. The bacterium that causes syphilis is transmitted via contact with toilet seats, soiled clothing, or other fomites. Evidence suggests that male circumcision reduces the risk of cervical cancer in female sexual partners. A person infected with herpesvirus but lacking blisters frequently spreads genital herpes in mucous secretions. Although usually sexually transmitted, trichomoniasis can be transferred via damp fomites. Label the following stages and structures of the chlamydia life cycle: elementary body, endocytosis, vesicle, host cell, inclusion body, reticulate body. A (0 hour) (f) (a) D ( ) (b) Short Answer 1. The normal microbiome of the female reproductive tract helps maintain a vaginal pH of about 4. If the urinary organs and the urine in them are usually axenic, why does normally voided urine contain bacteria What structure found in Neisseria gonorrhoeae allows the bacterium to attach to sperm cells and travel up the uterine tubes to produce pelvic inflammatory disease Why have scientists had problems identifying virulence factors of Treponema pallidum It has been observed that prepubescent girls are more susceptible to vaginal infections than adult women. Explain this observation, mentioning glycogen, lactic acid, pH, and estrogen in your discussion. Although vaginal douching is a cleansing procedure, it can actually promote infection. B ( ) (c) C ( ) (e) (d) Questions for review 775 2. Some scientists think that syphilis is a New World disease brought to Europe by returning Spanish explorers; others think that syphilis traveled the opposite way. Although laser surgery can successfully remove genital warts, some physicians are reluctant to choose this procedure. Discuss how the use of antimicrobials to prevent genital disease may have negative effects. After a patient complains that his eyes are extremely sensitive to light and feel gritty, his doctor informs him that he has ocular herpes. Why does treatment of strep throat with an antibacterial drug increase the chance for vaginal candidiasis Body-wide rash Cardiovascular syphilis Chancre Dark-field microscopy Infect fetus in pregnant woman Latent stage Neurosyphilis Never progress Penicillin Primary syphilis Secondary syphilis Serological tests Spirochete Tertiary syphilis Treponema pallidum Syphilis diagnosed by 14 caused by 1 4 begins with characterized by 5 treated with 15 may progress to 6 may progress to 8 Last for years may 9 may progress to 11 characterized by characterized by 7 10 causing Congenital syphilis Gummas 12 13 is 2 impossible to culture in Cell-free media viewed with 3 25 Applied and Industrial Microbiology A Case of Dehydration Mateo works as an architect and has just finished one of the biggest projects of his career. After work on Friday night, Mateo and some of his coworkers go out for a celebratory dinner at a local restaurant featuring food prepared by local artisanal chefs. He had sweated a lot on the bike ride, so he assumes that he is just a bit dehydrated and needs to drink more water. When Mateo wakes up on Sunday morning, he still has a dry mouth and is having a hard time swallowing. Bacteria and fungi in particular are capable of many metabolic processes that are useful to humans. In this article, we examine how the vast metabolic capability of microbes is harnessed to serve human needs. In addition to an initial starter culture, secondary cultures may be added to further modify the flavor or aroma of foods. For example, the same starter culture is used to initiate formation of both Swiss cheese and blue cheese; the two cheeses differ because different secondary cultures are used in their production. Bread Saccharomyces cerevisiae (sak-r-msz se-ri-vis-) metabolizes sugars to leaven1 bread. Bakers add the yeast to flour, salt, and other ingredients to make dough, which is kneaded to introduce oxygen. Sourdough bread is made using starter cultures consisting of yeast and lactic acid bacteria. Food Microbiology Microorganisms are involved in producing many of our favorite foods and beverages, from bread to wine to yogurt. Indeed, fermented foods are among the oldest foods known and are culturally very diverse. The characteristic flavors, aromas, and consistencies of such foods result from the presence of acids or sugars made by microbes during fermentation. Besides conferring taste and aroma, microbial metabolism also acts as a preservative, destroys many pathogenic microbes and toxins, and, in some cases, adds nutritional value in the form of vitamins or other nutrients. In the following sections, we explore how our knowledge of microbial growth and metabolism enables us to use microbes in food production and to control microbial activity that results in food spoilage. Most of these vegetable products are the result of the actions of lactic acid bacteria, such as Streptococcus (strep-t-koks), Leuconostoc (look-nos-tk), Lactobacillus (lakt-b-sils), or Lactococcus (lak-t-koks), which specifically produce lactic acid during fermentation. Lactic acid acidifies the food and produces a "sour" flavor, as in sourdough bread. Food products derived from the fermentation of cabbage include Korean kimchi (kim-ch) and German sauerkraut. Soy sauce is made by the fermentation of soybeans and wheat by lactobacilli, yeast (S. Coffee production relies on natural fermentation to release the coffee bean from the outer layers of the coffee berry so that the bean can then be dried and roasted. People often equate "pickles" with cucumbers, but other foods, such as beets and eggs, can also be pickled. Pickling refers to the process of preserving or flavoring foods with brine (saturated salt water) or acid. Microbial fermentation can be the source of the acid- as it is with dill pickles. Because pickled foods are acidic, few pathogenic microorganisms survive, making pickling an excellent preservation method. Silage, a product used as animal feed on many farms, is made by the natural fermentation of potatoes, corn, grass, grain stalks, or other types of green foliage. Under such moist, anaerobic conditions, the vegetation in the silos ferments, producing many organic compounds that make the silage aromatic and tasty to livestock and more easily digested by them. Biochemists use the word fermentation to refer to the partial oxidation of sugars to release energy using organic molecules as electron acceptors (see Chapter 5). In food microbiology, however, fermentation may refer to any desirable changes that occur to a food or beverage as a result of microbial growth. In contrast, spoilage denotes unwanted change to a food that occurs from undesirable metabolic reactions, the growth of pathogens, or the presence of unwanted microorganisms. In antiquity, people relied on these naturally occurring microbes to produce fermented foods and drinks. However, the same microbes are not always present on a food from harvest to harvest, yielding varying results. Most modern commercial food and beverage production relies on starter 1From Latin levare, meaning "to raise. The combination of fermentation and drying or smoking has been used for centuries to preserve meats, particularly pork and beef. Dry sausages, such as salami and pepperoni, are made by grinding meat, mixing in various spices and starter cultures, allowing the mixture to ferment in the cold, and then stuffing it into casings. Fermented fish-common in Asian countries-are prepared by grinding fish in brine. The solids are removed and pressed to form a fish paste, while the liquid portion is drained off and mixed with flavoring agents to form fish sauce. Addition of starter bacterial culture Coagulation of milk proteins (curd formation) Fermented Dairy Products Milk fermentation relies, for the most part, on the activities of lactic acid bacteria. Milk in an udder is sterile, but because milking introduces microorganisms, we pasteurize "raw" milk. The metabolic products of starter cultures give fermented milk products their characteristic textures and aromas. Buttermilk is made from fat-free milk (skim milk) by adding a starter culture of Lactococcus lactis (laktis) subspecies cremoris (kre-mris) and Leuconostoc citrovorum (sit-r-vrum). Yogurt production utilizes starter cultures of Streptococcus thermophilus (ther-mofil-us) and Lactobacillus bulgaricus (bulgri-ks). Yogurt manufacturers mix pasteurized milk, milk solids, sweeteners, and other ingredients to a uniform consistency and then add the starter culture. The microorganisms are left alive and may have beneficial effects; they are so-called probiotics; that is, live microorganisms administered to improve health and prevent disease. Cultures of Lactococcus lactis coagulate protein in milk to form curds (solids) and whey (liquids). For cheeses sold as soon as they are made (called unripened cheeses, such as cottage cheese), the curd is removed, cut into small pieces, and packaged. Alternatively, the curdling process can be accelerated by the addition of the enzyme rennin, a type of protease (protein-digesting enzyme). Rennin was originally obtained from the stomach of cud-chewing animals, but now most of it is produced by the genetically modified fungus Aspergillus. Other cheeses (so-called ripened cheeses) are aged until they have the desired texture or taste. Hard cheeses, such as Parmesan and cheddar, are pressed until little water remains, while soft cheeses retain enough moisture to make them spreadable. Once curds are pressed, a cheese is aged for months to years while continued microbial activity imparts characteristic smells and tastes.

Syndromes

• Abnormally dark or light skin
• Itching, pain, or bleeding with bowel movements
• Heart failure (type II)
• Certain types of moles (atypical or dysplastic) or multiple birthmarks
• Serum iron
• The skin on your breast appears dimpled or wrinkled (like the peel of an orange)
• Stomach pain
• Calcium deposits forming around the mitral valve
• You have a family history of IP and are considering having children

Anaerobic organisms then take over the water system diferencia entre antiviral y vacuna buy 5 gm zovirax cream otc, leading to an increased production of H2S and the release of foul odors antiviral drug list purchase zovirax cream 5 gm on-line. They rarely cause human disease hiv infection rates by race buy zovirax cream 5 gm online, though plant pathogens are prevalent in soils and are agriculturally and economically important hiv infection without fever purchase genuine zovirax cream line. The Nature of Soils Soil arises both from the weathering of rocks and through the actions of microorganisms infection rates of hiv cheap zovirax cream master card, which produce wastes and organic materials needed to support more complex life forms what is the hiv infection process purchase zovirax cream 5 gm amex, such as plants. Most microorganisms are found in topsoil, where the richness of the organic deposits sustain a large biomass. Topsoil itself, however, is highly heterogeneous, and therefore different kinds and amounts of microbes are found in various soils around the world. Because oxygen dissolves poorly in water, moist soils have a lower oxygen content than drier soils. Weather patterns also affect oxygen content, as the presence or absence of rainwater determines moisture and thus dissolved oxygen. Highly acidic and highly basic soils favor fungi over bacteria, though fungi typically prefer acidic conditions. Thus, most soil microbes live quite well in areas where winters and summers are not too extreme. Psychrophiles grow only in consistently cold environments and cannot survive in soils that experience spring thawing; the opposite is true for thermophiles, which cannot survive where winters are harsh. The biomass of a microbial community is determined more by the amount of organic material than by the kind of organic material: any soil that has a relatively constant input of organic material can support a wider array of microorganisms than soil that is more barren. Factors Affecting Microbial Abundance in Soils Several environmental factors influence the density and the composition of the microbiome within a soil, including the amount of water, availability of oxygen and other electron acceptors, acidity, temperature, and the availability of nutrients. Moisture is essential for microbial survival; microbes exhibit Microbial Populations in Soils Because of the variety of soils, microbial populations differ tremendously from soil to soil and even within the same soil over the course of a season. Bacteria are numerous, and diverse inhabitants of soil and are found in all soil layers. Archaea are present in soils, but the inability to culture many of them has limited our ability to study them. Free-living and symbiotic fungi are found only in topsoil, where they can form gigantic mycelia that cover acres. Soil algae live on or near the surface because, as photoautotrophs, they require light. Neither algae nor protozoa can withstand dramatic environmental changes or the introduction of pollutants. They cycle nitrogen, sulfur, phosphorus, and other elements, converting them into usable forms. Microbes degrade dead organisms and their wastes, and some can clean up industrial pollutants. Further, microbes produce an incredible variety of compounds that have potential human uses. Although topsoils in general are richer in nutrients and microbes than are subsoils, the nutrient and microbial content of topsoils is highly variable. Fusarium oxysporum Phytophthora cinnamomi Viruses Hantavirus Tobamovirus tobacco mosaic virus Furovirus soil-borne wheat mosaic virus Humans Plants Plants Hantavirus pulmonary syndrome Necrotic spots in various plants Mosaic disease in winter wheat and barley Humans Humans Humans Plants Plants Plants Histoplasmosis Blastomycosis Coccidioidomycosis Root rot in cereals Root rot in many plants Potato blight; root rot in many plants Humans Humans Plants Plants Plants Anthrax Tetanus Crown gall disease Potato wilt Potato scab Host Disease Soilborne Diseases of Humans and Plants Although the majority of soil microorganisms are harmless, there are exceptions. Soilborne infections of humans generally result from either direct contact with, ingestion of, or inhalation of microorganisms deposited in soil in animal or human feces or urine. In some cases, the microbes live and replicate in the soil, but in most cases soil is simply a vehicle for moving the pathogen from one host to another. Disturbing the soil can lead to infection if endospores enter cuts or abrasions on the skin (cutaneous anthrax) or are inhaled into the lungs (inhalation anthrax). Histoplasma grows in soil and is also deposited there as spores in the droppings of infected birds and bats. Microbial plant infections are generally characterized by one or more of the following signs: necrosis (rot), cankers/lesions, wilt (droopiness), blight (loss of foliage), galls (tumors), growth aberrations (too much or too little), or bleaching (loss of chlorophyll). Bacteria, fungi, and viruses all cause diseases in plants and spread either as airborne spores, through roots or wounds, or by insects. Types of Aquatic Habitats Aquatic habitats are divided primarily into freshwater and marine systems. Natural aquatic systems can be greatly affected by the release of so-called domestic water, which is water resulting from the treatment of sewage and industrial waste. Domestic water released into the environment affects water chemistry and the microorganisms living in the water. Furthermore, faulty treatment of sewage leads to contamination of natural water systems with pathogenic microorganisms. Freshwater Ecosystems Microorganisms become distributed vertically within lake systems according to oxygen availability, light intensity, and temperature. Aquatic microbiologists study microorganisms living in freshwater and marine environments. Compared to soil habitats, water ecosystems support fewer microbes overall because nutrients are diluted. Many organisms that live in aquatic systems exist in biofilms attached to surfaces. Both deep lakes and oceans can be divided into zones that vary with respect to light penetration, concentration of nutrients, temperature, and pressure-and thus the types and abundance of microorganisms. In large lakes, wave action continually mixes nutrients, oxygen, and organisms, which allows efficient utilization of resources. In stagnant waters, oxygen is readily depleted, resulting in more anaerobic metabolism and poorer water quality. It has a lesser oxygen content and more diffuse light than the previous two zones. Some photosynthetic organisms, such as purple and green sulfur bacteria, perform anaerobic photosynthesis here. Anaerobic bacteria in the sediments produce H2S, which is used by organisms nearer the surface. In contrast to lakes, streams and rivers are more uniform because organisms and nutrients are swept along and mixed. Biofilms are particularly important in moving waterways, and the majority of organisms live toward the edges, where surfaces are available, currents are less severe, and organic materials enter the water. Marine Ecosystems Marine ecosystems are typically nutrient poor, dark, cold, and subject to great pressure. Photoautotrophic prokaryotes, diatoms, dinoflagellates, and algae are found near the surface. Most marine waters are extreme environments inhabited only by highly specialized microorganisms. All microbes in marine systems must be salt tolerant and possess highly efficient nutrient-uptake mechanisms to compensate for the scarcity of nutrients. The majority of marine microorganisms are found in the littoral zone, where nutrient levels are high and light is available for photosynthesis. Even though the benthic and abyssal zones have sparse nutrients, they still support microbial growth, particularly around hydrothermal vents located in the abyssal zone. Such vents spew superheated, nutrient-rich water, providing nutrients and an energy source for thermophilic chemoautotrophic anaerobes, which in turn support a variety of invertebrate and vertebrate animals. Specialized Novel Aquatic Ecosystems In addition to the two broad categories of water systems just described, many distinctive aquatic ecosystems also exist, including salt lakes, iron springs, and sulfur springs. Each of these systems is inhabited by specialized microorganisms that are highly adapted to the conditions. Criteria for Assessing Biological Threats to Humans In the United States, the assessment of a potential biological threat to humans is based on the following four criteria: Public health impact. This criterion relates to the ability of hospitals and clinics to deal effectively with numerous casualties. The more casualties, the more difficult it is for hospitals and clinics to effectively respond to the needs of all patients. If an agent causes numerous serious cases, emergency response systems could be overwhelmed and even cease to function. If an agent is highly lethal, proper disposal of bodies might become difficult, which would contribute to the spread of disease. The more people that can be infected at one time, the more devastating a primary attack. If an introduced agent spreads on its own through a population, secondary and tertiary waves of illness will augment the number of casualties. Also assessed as part of delivery potential are ease of mass production (the easier an agent is to produce in quantity, the greater its potential threat), availability (the more prevalent it is in the environment, the easier it is to obtain and weaponize), and environmental stability (the longer it remains infective once released, the greater the threat). This criterion evaluates the effect of public fear on the ability of response personnel to control a disease outbreak following an attack. Agents with high mortality, few treatment options, and no vaccine instill greater fear into a populace, making quarantine (isolating infected and sick patients from the rest of the population) difficult to enforce. The resulting chaos could dramatically decrease the ability of response personnel to control disease transmission and treat patients. This criterion assesses existing response measures and attempts to identify improvements needed in the health care infrastructure to prepare for a biological attack. Diagnosis and recognition involve proper surveillance and training medical personnel to ascertain whether an attack has occurred. Once an attack has been confirmed, predetermined responses are required to reduce confusion and allow rapid control of the situation. Public health preparedness also involves funding for research and development of new vaccines, treatments, and diagnostic capabilities. When assessing a threat, government authorities assign each potential bioterrorist agent a score for each of the criteria. Biological Warfare and Bioterrorism the properties of microorganisms that allow scientists to manipulate organisms to make advancements in medicine, food production, and industry also enable humans to fashion microbes into biological weapons, which can be directed at people, livestock, or crops. A topic of growing concern is agroterrorism-the bioterrorist use of microbes to destroy a food supply. International treaties and laws of the United States, Great Britain, and other countries prohibit the use of biological weapons. Many microorganisms cause disease, but not all disease-causing organisms have potential as biological weapons. Governments Biological Warfare and Bioterrorism 813 Criteria for Assessing Biological Threats to Livestock and Poultry the criteria used to evaluate biological threats to livestock and poultry include agricultural impact, delivery potential, and analysis to determine if the outbreak is the result of terrorism or is a naturally occurring event. Infectious agents prove the most devastating for agricultural livestock kept in large herds or flocks. Many animal pathogens exist naturally in soil or are already endemic in livestock and poultry, so they can be easily obtained and readily grown in large quantities. The highly infectious nature of some agents means that by the time a disease is recognized, much of a herd is infected already, so all must be destroyed to control an outbreak. Further, some pathogens can persist in the soil even after the animals are destroyed. Many animal diseases are spread either by contact or by inhalation, thus making attack easier for a terrorist. Though highly contagious among animals, most are not infectious to humans, making them "safe" for terrorists to handle. Category C agents are potential threats; not enough is currently known about them to determine their true potential as weapons. Agents in all three categories are known as biological select agents or more simply as select agents. Fortunately, it is difficult for would-be terrorists to acquire viral samples for propagation; it also takes a high degree of skill, in addition to specific containment facilities, to work with smallpox virus. An effective vaccine is available, and the vaccine is effective when administered soon after infection. Animal Pathogens Biological agents against animals are also divided into categories, with category A agents being the most dangerous. Whereas many potential agents are spread via inhalation, others are spread by insect vectors, making them less likely to be used as weapons. Some agents infect wild animal populations in addition to livestock, potentially amplifying any outbreak that might occur. Foot-and-mouth disease virus, the most dangerous of potential agroterrorism agents, affects all wild and domestic cloven-hoofed animals. Humans can transport it from herd to herd on their person, on farm equipment, or through the movement of animals between auctions and farms. Any appearance of foot-and-mouth disease on a farm requires destruction of entire herds, complete disinfection of all areas occupied by the herd, and disposal of all animals by burning or burial. Criteria for Assessing Biological Threats to Agricultural Crops Plant diseases are generally not as contagious as animal or human diseases. Threats to crops are evaluated on predicted extent of crop loss, delivery and dissemination potential, and containment potential. Plant pathogens that either cause severe crop loss or produce toxins are considered the greatest threats. Such agents already exist in the environment and can be readily obtained; however, plant pathogens are not as easily mass-produced as animal agents. Plant pathogens that can be spread systematically through fields by natural means, such as through contaminated soil or by insects, could remain in the environment even after destruction of the target crop. Successive plantings in contaminated fields could result in continued crop loss for as long as the agent persists. Because the causes of many plant diseases are not easily diagnosed, such a pathogen could be widely disseminated before response measures are instituted. Economic losses would be staggering, particularly given that embargos on affected crops would likely remain in place for years after an attack. Plant Pathogens Many plant pathogens exist, but the categorization of plant pathogens as terrorist agents lags behind similar efforts for humans and animals.

In an active cell hiv infection rates gay generic zovirax cream 5 gm otc, the arginine will be used immediately garlic antiviral zovirax cream 5 gm with mastercard, and the repressor will remain inactive (unable to bind the operator) because there is too little free arginine to activate it hiv infection cdc trusted zovirax cream 5 gm. The free arginine is then available to act as a corepressor by attaching to the repressor hiv infection origin order zovirax cream with visa. This reaction changes the shape of the repressor hiv infection rate in sierra leone purchase zovirax cream online, making it capable of binding to the operator antiviral and antiretroviral order 5 gm zovirax cream overnight delivery. In eukaryotic cells, gene function can be altered by intrinsic regulatory segments similar to operons. These transcription factors can regulate gene expression in response to environmental stimuli such as nutrients, toxin levels, or even temperature. Eukaryotic genes are also regulated during growth and development, leading to the hundreds of different tissue types found in higher multicellular organisms. Phase Variation When bacteria turn on or turn off a set of genes that leads to obvious phenotypic changes, it is sometimes called phase variation. Phase variation is a type of phenotypic variation that is heritable-meaning it is passed down to subsequent generations-but may be further changed as it passes to subsequent generations. This process involves the turning on of genes mediated by regulatory proteins, as described with operons. Treatment with such drugs is based on an important premise: that growth of the bacterium will be inhibited by blocking its protein-synthesizing machinery selectively, without disrupting the cell synthesis of the patient receiving the therapy. Drugs that inhibit protein synthesis may exert their influence on transcription or translation. For this reason, it is very toxic and never used to treat bacterial infections, though it can be applied in tumor treatment. The ribosome is a frequent target of antibiotics that inhibit ribosomal function and ultimately protein synthesis. The value and safety of these antibiotics again depend upon the differential susceptibility of bacterial and eukaryotic ribosomes. Chloramphenicol, lincomycin, and tetracycline bind to the ribosome in a way that blocks the elongation of the polypeptide, and aminoglycosides (such as streptomycin) inhibit peptide initiation and elongation. A repressible operon remains on when its nutrient products (here, arginine) are in great demand by the cell because the repressor is unable to bind to the operator at low nutrient levels. Differentiate between repressible and inducible operons and provide an example of each. List several antibiotic drugs and their targets within the transcription and translation machinery. The operon is repressed when (1) arginine builds up and, serving as a corepressor, activates the repressor. Although bacteria have no exact equivalent to sexual reproduction, they exhibit a primitive means for sharing or recombining parts of their genome. Examples of phase variation include the ability of Neisseria gonorrhoeae strains to produce attachment fimbriae and the ability of Streptococcus pneumoniae to produce a capsule. They provide additional genes for resistance to drugs and metabolic poisons, new nutritional and metabolic capabilities, and increased virulence and adaptation to the environment. In general, any organism that contains (and expresses) genes that originated in another organism is called a recombinant. Conjugation: Bacterial "Sex" Conjugation is a mode of genetic exchange in which a plasmid or other genetic material is transferred by a donor cell to a recipient cell via a direct connection (figure 9. In gram-negative cells, the donor has a plasmid known as the fertility (F) factor that allows the synthesis of a conjugative pilus. Contact is made when a pilus grows out from the F+ cell, attaches to the surface of the F- cell, contracts, and draws the two cells together (as shown in figure 9. Conjugation is a conservative process, in that the donor bacterium generally retains ("conserves") a copy of the genetic material being transferred. There are many different kinds conjugative plasmids with some variations in their properties. The donor (F+) cell makes a copy of its F factor and transmits this to a recipient (F-) cell. The F- cell is thereby changed into an F+ cell capable of producing a pilus and conjugating with other cells. In a variation on that process, called high-frequency recombination (Hfr), the plasmid becomes integrated into the donor chromosome before instigating transfer to the recipient cell. The term high-frequency recombination was adopted to denote a cell with an integrated F factor that transmits its chromosomal genes. These genes become integrated into recipient chromosomes at a very high frequency. The F factor can direct a more comprehensive transfer of part of the donor chromosome to a recipient cell. It is now becoming clear that eukaryotic organisms-including humans-also engage in horizontal gene transfer, often aided and abetted by microbes such as viruses. This revelation has upended traditional views about eukaryotic evolution, taxonomy, and even "human-ness. Here, we will study the mechanisms used by bacteria to acquire genes horizontally. Plasmids are found in many bacteria (as well as some fungi) and typically contain, at most, only a few dozen genes. Although plasmids are not usually necessary for bacterial survival, they often carry useful traits, such as antibiotic resistance. Chromosomal fragments that have escaped from a lysed bacterial cell are also commonly involved in the transfer of genetic information between cells. An important difference between plasmids and fragments is that while a plasmid has its own origin of replication and is stably replicated and inherited, chromosomal fragments must integrate themselves into the bacterial chromosome in order to be replicated and eventually passed to progeny cells. Depending on the mode of transmission, the means of genetic recombination in bacteria is called conjugation, transformation, or transduction. The plasmid jumps into the chromosome, and when the chromosome is duplicated the plasmid and part of the chromosome are transmitted to a new cell through conjugation. Special resistance (R) plasmids, or factors, that carry genes for resisting antibiotics and other drugs are commonly shared among bacteria through conjugation. Transfer of R factors can confer multiple resistance to antibiotics such as tetracycline, chloramphenicol, streptomycin, sulfonamides, and penicillin. Other types of R factors carry genes for resistance to heavy metals (nickel and mercury) or for synthesizing virulence factors (toxins, enzymes, and adhesion molecules) that increase the pathogenicity of the bacterial strain. Cells that are capable of accepting genetic material through this means are termed competent. Transformation is a natural event found in several groups of gram-positive and gram-negative bacterial species. The experiment was conducted in the late 1920s by the English biochemist Frederick Griffith working with Streptococcus pneumoniae and laboratory mice. This bacterium exists in two different forms: (1) those that have a capsule have a smooth (S), glassy colony appearance, and are capable of causing severe disease; and (2) those that do not have a capsule have a rough (R) colony appearance and are nonpathogenic. Mice injected with a live, nonvirulent (R) strain remained alive and healthy (figure 9. First, he heat-killed an S strain and injected it into mice, which remained healthy (figure 9. Then came the ultimate test: Griffith injected both dead S cells and live R cells into mice, with the result that the mice died from pneumococcal blood infection (figure 9. If killed bacterial cells do not come back to life and the nonvirulent live strain was harmless, why did the mice die With this technique, foreign genes from a completely unrelated organism are inserted into a plasmid, which is then introduced into a competent bacterial cell through transformation. These recombinations can be carried out in a test tube, and human genes can be experimented upon and even expressed outside the human body by placing them in a microbial cell. This same phenomenon in eukaryotic cells, termed transfection, is an essential aspect of genetically engineered yeasts, plants, and mice. The participating bacteria in a single transduction event must be the same species because of the specificity of viruses for host cells. This specificity is explained by the prior existence of a temperate prophage inserted in a fixed site on the bacterial chromosome. During a lytic cycle, these specific viral-host gene combinations are incorporated into the viral particles and carried to another bacterial cell. The virulent strains of bacteria such as Corynebacterium diphtheriae, Clostridium spp. It turns out that the toxins are produced by bacteriophage genes that have been introduced by transduction. McClintock in 1951, it was greeted with nearly universal skepticism because it had long been believed that the location of a given gene was set and that genes did not or could not move around. For example, a pigmented bacterium can lose its ability to form pigment, or a strain of the malarial parasite can develop resistance to a drug. Mutations are most noticeable when the genotypic change leads to a change in phenotype. Mutations can involve the loss of base pairs, the addition of base pairs, or a rearrangement in the order of base pairs. This is different from genetic recombination, in which microbes transfer whole segments of genetic information among themselves. A microorganism that exhibits a natural, nonmutated characteristic is known as a wild type, or wild strain with respect to that trait. You may ask, In a constantly changing population of microbes, what is the natural, nonmutated state For that reason, most scientists prefer to define wild type as the trait present in the highest numbers in a population. Mutant strains can show variance in morphology, nutritional characteristics, genetic control mechanisms, resistance to chemicals, temperature preference, or nearly any type of enzymatic function. Mutant strains are very useful for tracking genetic events, unraveling genetic organization, and pinpointing genetic markers. A classic method of detecting mutant strains involves addition of various nutrients to a culture to screen for its use of that nutrient. For example, in a culture of a wild-type bacterium that is lactose-positive (meaning it has the necessary enzymes for fermenting this sugar), a small number of mutant cells have become lactose-negative, having lost the capacity to ferment this sugar. If the culture is plated on a medium containing indicators for fermentation, each colony can be observed for its fermentation reaction and the negative strain isolated. Some of the horizontally transferred genes in bacteria have the ability to make their new hosts pathogenic, or able to cause disease. These islands contain multiple genes that are coordinated to create a new trait in the bacterium, such as the ability to scavenge iron (important for the bacterium causing the plague, Yersinia pestis) or the ability to produce exotoxins (seen in Staphylococcus aureus). Data from these studies have shown that organisms "share" their genes, sometimes in great chunks, with one another, essentially leap-frogging the evolution process by shuffling genes in this manner. Mutation rates vary tremendously, from one mutation in 105 replications (a high rate) to one mutation in 1010 replications (a low rate). The rapid rate of bacterial reproduction allows these mutations to be observed more readily in bacteria than in most eukaryotes. These latter mutations, which involve addition, deletion, or substitution of single bases, are called point mutations. A change in a protein can likewise change the morphology and physiology of a cell. Some mutations have a harmful effect on the cell, leading to cell dysfunction or death; these are called lethal mutations. Of course, mutations can also be beneficial if they provide the cell with a useful change in structure or physiology. Any change in the code that leads to placement of a different amino acid is called a missense mutation (table 9. A nonsense mutation, on the other hand, changes a normal codon into a stop codon that does not code for an amino acid and stops the production of the protein wherever it occurs. A back-mutation occurs when a gene that has undergone mutation reverses (mutates back) to its original base composition. This type of cancer-causing agents, when vertebrates are exposed to them (see "The Ames Test" later in this section). Exposure to large doses of radiation can be fatal, which is why radiation is so effective in microbial control; it can also be carcinogenic in animals. This means that it is possible for living organisms similar to our own to be there, as well. A report released by the United States National Academy of Sciences in 2014 pointed out that we do not really know what would happen to our microbiome if we spent significant time in space. As you know, the human microbiome is a product of our diets and our interactions with other species and their microbiomes. In space, our diet is likely to be different, our interactions with other species are likely to be different, and then there are the different environmental conditions in space- weightlessness, for example. The report cited a study that showed that a Salmonella species alters its genomes after a few days in space, making it more virulent. Current studies are looking at how actual infections in space play out, how antibiotics work on microbes in space, and how the human microbiome differs in space. Maybe, if we discover bacteria that are native to space-on Mars, for example-they can teach us much more about what we can expect as we colonize the exoplanet. Normal gene Missense mutation: leading to amino acid switch (may or may not function well) Base substitution: silent (no change in function) (a) (b) (c) and the sugar phosphate strand at the site of the error. A repair system can also locate mismatched bases that were missed during proofreading, for example, C mistakenly paired with A, or G with T. The base must be replaced soon after the mismatch is made, or it will not be recognized by the repair enzymes. The Ames Test New agricultural, industrial, and medicinal chemicals are constantly Both lead to frameshifts Frameshift and premature stop being added to the environment, and and can lead to exposure to them is widespread. Although animal testing has Frameshift been a standard method of detecting chemicals with carcinogenic potenmutation, known as a frameshift (table 9. In this test, the experimental subjects are bacteria whose tions nearly always result in a nonfunctional protein because every gene expression and mutation rate can be readily observed and moniamino acid after the mutation is different from what was coded for tored.

One very clear advantage of cell culture is that a specific cell line can be available for viruses with a very narrow host range hiv infection worldwide zovirax cream 5 gm with amex. Ongoing worries about influenza pandemics and the need for vaccines have prompted scientists to look for faster and more efficient ways to grow the vaccine strains of influenza virus hiv infection in pregnancy zovirax cream 5 gm sale, which has been grown in chicken eggs since the 1950s general symptoms hiv infection zovirax cream 5 gm online. Around 2009 hiv infection statistics in kenya zovirax cream 5 gm otc, scientists succeeded in propagating the viruses in a continuous cell line derived from animal kidney cells hiv infection rate nigeria discount zovirax cream express. Since then ginger antiviral generic zovirax cream 5 gm with mastercard, influenza vaccines have been produced from both cell culture and from chicken eggs. One way to detect the growth of a virus in culture is to observe degeneration and lysis of infected cells in the monolayer of cells. The areas where virus-infected cells have been destroyed show up as clear, well-defined patches in the cell sheet called plaques (figure 6. This same technique is used to detect and count bacteriophages, because they also produce plaques when grown in soft agar cultures of their host cells (bacteria). A plaque develops when the viruses released by an infected host cell radiate out to adjacent host cells (figure 6. As this process continues, the infection spreads gradually and symmetrically from the original point of infection, causing the macroscopic appearance of round, clear spaces that correspond to areas of dead cells. One group of unusual forms, even smaller and simpler than viruses, is implicated in chronic, persistent diseases in humans and animals. These diseases are called spongiform encephalopathies because the brain tissue removed from affected animals resembles a sponge. The infection has a long period of latency (usually several years) before the first clinical signs appear. A common feature of these conditions is the deposition of distinct protein fibrils in the brain tissue. Researchers have determined that these fibrils are the agents of the disease and have named them prions (pree-onz). This was the first incidence of prion disease transmission from animals to humans. Several hundred Europeans developed symptoms of a variant form of Creutzfeldt-Jakob disease, leading to strict governmental controls on exporting cattle and beef products. One of the most compelling questions is just how a prion could be replicated, because all other infectious agents require some nucleic acid. Other fascinating viruslike agents in human disease are defective forms called satellite viruses that are actually dependent on other viruses for replication. Viroids are significant pathogens in several economically important plants, including tomatoes, potatoes, cucumbers, citrus trees, and chrysanthemums. Although most viral infections do not result in death, some, such as rabies or Ebola, have very high mortality rates, and others can lead to long-term debility (polio, neonatal rubella). The nature of viruses makes it difficult to design effective therapies against them. Because viruses are not bacteria, antibiotics aimed at disrupting bacterial cells do not work on them. Out of necessity, many antiviral drugs block virus replication by targeting the function of host cells and for that reason can cause severe side effects. Almost all currently used antiviral drugs are designed to target one of the steps in the viral life cycle you learned about earlier in this chapter. Because viral drugs are often less effective than antibiotics are with bacteria, scientists historically put a lot of effort into developing vaccines against viral diseases. We have completed our survey of bacteria, archaea, eukaryotes, and viruses and have described characteristics of different representatives of these four groups. As we continue, we will explore how microorganisms maintain themselves, beginning with nutrition and then looking into microbial metabolism. Certainly, viruses are the most common cause of acute infections that do not result in hospitalization, especially when one considers widespread diseases such as colds, chickenpox, influenza, herpes, and warts. Discuss the primary reason that antiviral drugs are more difficult to design than antibacterial drugs. Media Under the Microscope Wrap-Up the intended message of this article is that it is possible that infection with a certain virus can affect our cognitive abilities. There is certainly a secondary message, as well-which is that viruses have much more widespread effects than we previously thought. It sounds very intriguing, but how does a layperson begin to assess whether it is possible One plus: the article references another virus that has been shown to be associated with cognitive decreases (the herpes simplex virus). That is one good way to support a new finding-to show that it has been found (with other "players") before. The scientists suggested that infection with the virus could lead to lower intelligence. I cannot find a reason to give it an A, because there just was not enough in it to make any kind of judgment about its accuracy. It does say that the research was published in the Proceedings of the National Academy of Sciences, but it does not give the actual reference indicating when it was published. They are not alive, yet they are able to redirect the metabolism of living cells to reproduce virus particles. Viral replication inside a cell usually causes death or loss of function of that cell. Spikes on the surface of the virus capsid or envelope are critical for their attachment to host cells. This textbook uses their structure, genetic composition, and host range to categorize them. The International Committee on the Taxonomy of Viruses oversees naming and classification of viruses. These events turn the host cell into a factory solely for making and shedding new viruses. Bacteriophages vary significantly from animal viruses in their methods of adsorption, penetration, site of replication, and method of exit from host cells. It is replicated right along with the chromosome every time the bacterium divides. Cell and tissue cultures are cultures of host cells grown in special sterile chambers containing correct types and proportions of growth factors using aseptic techniques to exclude unwanted 100 m microorganisms. It is conceivable that many chronic diseases of unknown cause will eventually be connected to viral agents. Viral infections are difficult to treat because the drugs that attack viral replication also cause side effects in the host. Chapter Summary 163 High Impact Study these terms and concepts are most critical for your understanding of this chapter-and may be the most difficult. Circle the viral infections from this list: cholera, rabies, plague, cold sores, whooping cough, tetanus, genital warts, gonorrhea, mumps, Rocky Mountain spotted fever, syphilis, rubella. The envelope of an animal virus is derived from the peptidoglycan of its host cell. The nucleic acid of animal viruses enters the cell through a process called translocation. Viruses that persist in the (host) cell and cause recurrent disease are called latent. Clear patches in cell cultures that indicate sites of virus infection are called a. Provide evidence in support of or refuting the following statement: Viruses are simple cellular agents of disease. Summarize the unique properties of viruses and explain which of these characteristics allow them to function as "parasites. Compare and contrast the processes of latency and lysogeny, providing examples of latent viruses and lysogenic viruses. Use the Internet to search prion diseases, and identify three major differences between a viral disease and a prion disease. Using the words that follow, please create a concept map illustrating the relationships among these key terms from chapter 6. This opening case examines an article from the popular media to determine the extent to which it is factual and/or misleading. This article described their early, and successful, attempt to power a Samsung cell phone with urine. The key was microbes, which utilized chemicals in the urine during their own growth processes, and in so doing produced energy through a device called a microbial fuel cell. The microbes consume part of the urine, which generates electrons that when connected to a cathode, create an electric current. The researchers wanted to scale-up their production of electricity so that there would be enough to power the lights for a house in poor or remote areas of the world. Discuss characteristics of biofilms that differentiate them from planktonic bacteria and their infections. Identify one quantitative and one qualitative method used for analyzing bacterial growth. But the ultimate source of a particular element, its chemical form, and how much of it the microbe needs are all points of variation between different types of organisms. Any substance, whether in elemental or molecular form, that must be provided to an organism is called an essential nutrient. For microbes, the essential nutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus (phosphate), and sulfur-often Disease Connection What essential nutrients do humans need to survive The micronutrients needed for humans to survive are the vitamins A, C, D, E, and K, as well as the B-complex vitamins. Minerals include calcium, potassium, chloride, phosphorus, sodium, and magnesium (also known as electrolytes), as well as copper, cobalt, zinc, chromium, iron, and fluoride (which make up the trace elements). As you can see, we actually have a few essential nutrients in common with microbes! Once absorbed, nutrients are processed and transformed into the chemicals of the cell. Macronutrients are required in relatively large quantities and play principal roles in cell structure and metabolism. Micronutrients, or trace elements, such as manganese, zinc, and nickel, are present in much smaller amounts and are involved in enzyme function and maintenance of protein structure. An inorganic nutrient is an atom or simple molecule that contains a combination of atoms other than carbon and hydrogen. The natural reservoirs of inorganic compounds are mineral deposits in the crust of the earth, bodies of water, and the atmosphere. Examples include metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide), and water (table 7. In contrast, the molecules of organic nutrients contain carbon and hydrogen atoms and are usually the products of living things. The source of nutrients is extremely varied: Some microbes obtain their nutrients entirely from inorganic sources, and others require a combination of organic and inorganic sources. Parasites capable of invading and living on the human body derive all essential nutrients from host tissues, tissue fluids, secretions, and wastes. Chemical Analysis of Microbial Cytoplasm Examining the chemical composition of a bacterial cell can indicate its nutritional requirements. Some of these components are absorbed in a ready-to-use form, and others must be 168 Chapter 7 Microbial Nutrition, Ecology, and Growth Table 7. The following are important features of cell composition: Water is the most abundant of all the components (70% of cell contents). When cell contents are considered after the removal of water, we call it "dry weight. Chemical elements are needed in the overall scheme of cell growth, but most of them are available to the cell as compounds and not as pure elements (see table 7. Sources of Essential Nutrients In their most basic form, elements that make up nutrients exist in inorganic reservoirs. These reservoirs not only serve as a permanent, long-term source of these elements but also can be replenished by the activities of organisms. You will no doubt notice that some categories overlap and that many of the compounds furnish more than one element. Carbon Sources It seems worthwhile to emphasize a point about the extracellular source of carbon as opposed to the intracellular function of carbon compounds. Although a distinction is made between the type of carbon compound cells absorb as nutrients (inorganic or organic), the majority of carbon compounds involved in the normal structure and metabolism of all cells are organic. Because organic carbon originates from the bodies of other organisms, heterotrophs are dependent on other life forms (hetero- is a Greek prefix meaning "other"). Among the common organic molecules that can satisfy this requirement are proteins, carbohydrates, lipids, and nucleic acids. Some organic nutrients available to heterotrophs already exist in a form that is simple enough for absorption. Moreover, heterotrophs vary in their capacities to use different organic carbon sources. Some are restricted to a few substrates, whereas others (certain Pseudomonas species, for example) are so versatile that they can metabolize more than 100 different substrates. It does not cause disease in healthy humans, but in immunocompromised patients, it is a major pathogen. Sulfur is an essential component of some vitamins (vitamin B1) and the amino acids methionine and cysteine; the latter help determine shape and structural stability of proteins by forming unique linkages called disulfide bonds.

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