Test 2 Flashcards

Question

- Unusual Forms of Medically Significant Bacteria: Rickettsia and Chymadia - Archaea - Genus Clostridium - Tetanus - Pathology - Treatment and Prevention

Answer 1

- Obligate intracellular parasites: Rickettsias - very tiny, gram-negative bacteria, Rickettsia rickettisii (rock mountain spotted fever) - Chlamydias: tiny (chlamydia trachmatis (severe eye infection and sexually transmitted disease) - Constitute third Domain Archaea - More closely related to Eukarya than to Bacteria - Contain unique genetic sequences in their rRNA - Have unique membrane lipids and cell walls - Live in the most extreme habitats in nature, extremophiles - Adapted to heat, salt, acid pH, pressure, and atmosphere -Includes: methane producers, hyperthermophiles, extreme ealohiles, and sulfur reducers - Gram-positive, spore-forming rods - Anaerobic - catalase negative - 120 species: saprobes --> free living; commensals of humans and animals; several pathogens - Oval or spherical spores produced only under anaerobic conditions - Synthesize organic acids, alcohols, and exotoxins - Two types of infections: wound infections and tissues infections, food intoxications - Clostridium Tetani --> Common resident of soil and GI tracts of animals, causes tetanus or lockjaw - neuromuscular disease, most commonly among geriatric patients and IV drug abusers - neonates in developing countries - Pathology: Spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts - Anaerobic environment required for vegetative cells to grow and release toxin - Tetanospasmin: very potent A-B toxin, neurotoxin causes paralysis by binding to motor nerve endings and blocking release of neurotransmitter for muscular contraction inhibition, muscles contract uncontrollably - Death most often due to paralysis of respiratory muscles - Treatment aimed at deterring degree of toxemia and infection and maintaining homeostasis - Antitoxin therapy with human tetanus immune globulin --> inactivates circulating toxin but does not counteract that which is already bound to neurons - Control infection with penicillin or tetracycline - Supportive care: muscle relaxants, sometimes a respirator and tracheostomy - Vaccine available - booster needed every 10 Yeats - Part of the DTaP vaccine - Tetanus toxoid

Answer 2

``` Gram-positive, endospore-forming, motile rods, Mostly saprobic (decomposing) – Versatile in degrading complex macromolecules – Primary habitat - soil • Aerobic – Catalase positive • Source of antibiotics • 2 species of medical importance: – Bacillus anthracis – Bacillus cereus ``` Large, block-shaped rods --> Facultative anaerobe, Central spores that develop under all conditions except in the living tissue • Primarily a zoonotic disease • Virulence factors – polypeptide capsule – Exotoxins = protective antigen, edema factor, lethal factor • Causative agent of anthrax 3 types of anthrax: – Cutaneous – spores enter through skin, black sore/eschar (dead tissue) • most common and least dangerous – Pulmonary– inhalation of spores – Gastrointestinal – ingested spores -Control and Treatment: -Two important considerations in treatment: – Kill the bacteria • Treated with antibiotics: clindamycin, doxycycline, ciprofloxacin – Inactivate the toxin • New drug raxibacumab: antibody that binds one of the toxins produced by B. anthracis • Vaccines – Live attenuated spores and toxoid (inactivated exotoxin) to protect livestock – Purified toxoid; for high risk occupations and military personnel; toxoid 5 inoculations over 1.5 years; annual boosters • Animals that die of anthrax are burned or chemically decontaminated before burial

Answer 3

- Mild intestinal illness --> 2nd common most common form of food poisoning worldwide - Food left to stand too long after cooking - Rare but severe intoxication usually from home canned food - Botulism disease occurs form botulinum toxin - Botulism: intoxication associated with inadequate food preservation - Spore-forming anaerobe --> commonly inhabits soil and water - Pathogenesis: Classic Case - home canners - Spores are present on food when gathered and processed - If reliable temperature and pressure are not achieved, air will be evacuated but spores will remain - Anaerobic conditions favor spore germination and vegetative growth - Potent toxin, botulin, is released - Disease mostly from ingested toxin, in some instances, due to active infection - Botulism: botulin toxin is carried to neuromuscular junctions and blocks the release of acetylcholine necessary for muscle contraction to occur - A-B toxin: active component is protease - most potent neurotoxin known -Infant botulism: Caused by ingested spores that germinate and release toxin --> flaccid paralysis - Wound botulism: spores enter wound --> release toxin - Similar symptoms to food intoxication caused by ingestion of botulin - Treatment/prevention: determine presecene of toxin in food, intestinal contents, or feces; administer antitoxin - cardiac and respiratory support, infectious botulism treated with penicillin; practice proper methods of preserving and handling canned foods, addition of preservatives

Answer 4

-Protozoa, Fungi, Algae, Helminths, Arthropods, etc. - External: Appendages (flagella and cilia), Glycocalyx (capsules and slimes) - Boundary: Cell wall/cytoplasmic membrane - Internal: Cytoplasmic membrane, nucleus (nuclear envelope, nucleolus, chromosomes), organelles (ER, Golgi, Mitochondria, and Choloroplasts), ribosomes, cytoskeleton (microtubules and microfilaments)

Answer 5

-Nucleus: Compact sphere, most prominent organelle of eukaryotic cell – Nuclear envelope composed of two parallel membranes separated by a narrow space and is perforated with pores, Contains chromosomes – Nucleolus – dark area for rRNA synthesis and ribosome assembly -Endoplasmic Reticulum - 2 types: – Rough endoplasmic reticulum (RER) – originates from the outer membrane of the nuclear envelope and extends in a continuous network through cytoplasm; rough due to ribosomes; proteins synthesized and shunted into the ER for packaging and transport; first step in secretory pathway – Smooth endoplasmic reticulum (SER) – closed tubular network without ribosomes; functions in nutrient processing, synthesis, and storage of lipids -Golgi Apparatus: Consists of a stack of flattened sacs called cisternae --> Modifies, stores, and packages proteins -Transport Processes: Transitional vesicles from the ER containing proteins go to the Golgi apparatus for modification and maturation – Condensing vesicles transport proteins to organelles or secretory proteins to the outside **nucleus → RER → Golgi → vesicles → secretion** -Lysosomes: Vesicles containing enzymes that originate from Golgi apparatus --> Involved in intracellular digestion of food particles and in protection against invading microbes * Vacuoles: Membrane bound sacs containing particles to be digested, excreted, or stored * Phagosome: vacuole merged with a lysosome -Mitochondria: Function in energy production --> Consist of an outer membrane and an inner membrane with folds called cristae --> Cristae hold the enzymes and electron carriers of aerobic respiration – Divide independently of cell (Contain DNA and prokaryotic ribosomes) ----> Evolved from bacterial cell similar to Rickettsias -Chloroplast: Convert the energy of sunlight into chemical energy through photosynthesis (Found in algae and plant cells) --> Outer membrane covers inner membrane that is folded into sacs, thylakoids, stacked into grana – Primary producers of organic nutrients for other organisms --> Evolved from cyanobacteria • Ribosomes: Composed of rRNA and proteins –> Scattered in cytoplasm or associated with RER, Larger than prokaryotic ribosomes [80S (60S + 40S)] – Function in protein synthesis -Cytoskeleton: Flexible framework of proteins, microfilaments and microtubules form network throughout cytoplasm --> Involved in movement of cytoplasm, amoeboid movement, transport, and structural support

Answer 6

-Cell Wall: – Rigid, provides structural support and shape – Fungi have thick inner layer of polysaccharide fibers composed of chitin or cellulose and a thin layer of mixed glycans – Algae – varies in chemical composition; substances commonly found include cellulose, pectin, mannans, silicon dioxide, and calcium carbonate Cytoplasmic (cell) membrane: Typical bilayer of phospholipids and proteins (Sterols confer stability) --> Serves as selectively permeable barrier in transport –>Eukaryotic cells also contain membrane-bound organelles that account for 60-80% of their volume

Answer 7

- Locomotor appendages: Flagella (Long, sheathed cylinder containing microtubules in a 9+2 arrangement), Covered by an extension of the cell membrane, 10X thicker than prokaryotic flagella --> Function in motility - Cilia: Similar in overall structure to flagella, but shorter and more numerous, Found only on a single group of protozoa and certain animal cells--> Function in motility, feeding, and filtering Glycocalyx: An outermost boundary that comes into direct contact with environment (Usually composed of polysaccharides) --> Appears as a network of fibers, a slime layer or a capsule – Functions in adherence, protection, and signal reception – Beneath the glycocalyx: Fungi and most algae have a thick, rigid cell wall; Protozoa, a few algae, and all animal cells lack a cell wall and have only a membrane

Answer 8

-Kingdom Fungi: – Majority are unicellular or colonial; a few have cellular specialization --> 100,000 species divided into 2 groups: – Macroscopic fungi (mushrooms, puffballs, gill fungi) – Microscopic fungi (molds, yeasts) - exist in 2 morphologies: yeast (round ovoid shape, asexual reproduction (buds)) and hyphae (long filamentous fungi or molds) •Some exist in either form – dimorphic – characteristic of some pathogenic molds -All fungi are heterotrophic --> Majority are harmless saprobes living off dead plants and animals (Extremely widespread distribution in many habitats) • Some are parasites, living on the tissues of other organisms, but none are obligate --> Mycoses – fungal infections - White nose syndrome: Mass extinction of bats in the easter US due to a fungal infection (Pseudogymnoascys destructans -- related to geqmyces) - -> Spread by direct contact -- afflicts primarily bat species that hibernate during winter months -Fungal Neighbors: Fungal spores are EVERYWHERE, though germination conditions may be quite specific. • Many are harmless, but others can cause ‘sick building syndrome’ (infection and fungal produced toxins) -Fungal Organization: -Yeast – soft, uniform texture and appearance –> Reproduce through an asexual process called budding -Filamentous fungi – mass of hyphae called mycelium; cottony, hairy, or velvety texture – Hyphae may be divided by cross walls – septate – Vegetative hyphae – digest and absorb nutrients – Reproductive hyphae – produce spores for reproduction -Fungal Reproduction --> Primarily through spores formed on reproductive hyphae • Asexual reproduction – spores are formed through budding or mitosis --> conidia or sporangiospores • Sexual reproduction – spores are formed following fusion of two different strains and formation of sexual structure (Zygospores, ascospores, and basidiospores) • Sexual spores and spore-forming structures are one basis for classification • Haploid – Single copy of genome –> meiosis – cell division without duplication of genome resulting in haploid cells • Diploid – Two copies of genome -Formation of zygospores - (+ and - contact mating hyphae) --> gametangia --> fertilization --> zygospore forms --> zygospore matures --> germination --> germinating zygospores - Basidospores = mushroom - Zygospores = bread mold

Answer 9

``` -Kingdom Eumycota is subdivided into several phyla • Phylum Zygomycota – – Hyphae usually nonsepate – zygospores; mostly sporangiospores and some conidia • Phylum Ascomycota – – Hyphae with porous septa – ascospores; conidia • Phylum Basidiomycota – – Incompletely septate hyphae – basidiospores; conidia • Phylum Chytridomycota – – Do not form hyphae – flagellated spores • Fungi that produce only Asexual Spores (Imperfect) ``` • Isolation on specific media (ex: Sabouraud’s agar) • Macroscopic and microscopic observation of: – Sexual and Asexual spore-forming structures and spores – Hyphal type – Colony texture and pigmentation – Physiological characteristics – Genetic makeup • Fungi do not readily enter sexual reproductive cycle in lab setting (ex. Fungi Imperfecti) * Adverse impact (includes Mycoses, allergies, toxin production; Destruction of crops and food storages) * Beneficial impact (Decomposers of dead plants and animals; Sources of antibiotics, alcohol, organic acids, vitamins; Used in making foods and in genetic studies) -Fungi can grow and divide by mitosis, can reproduce asexually to sexually (not all fungi show both forms, sexual reproduction involves two haploid cells merging to form a diploid cell --> later, through meiosis, haploid spores are formed), SPORES ARE A FORM OF REPRODUCTION AND SURVIVAL --> method of spore formation differs among fungi and is used as a means of classification (ex. sexual vs asexual, spore forming structure).

Answer 10

•Molds and yeasts are widely distributed in air, dust, fomites, and normal flora --> Humans are relatively resistant and Fungi are relatively nonpathogenic • Of the 100,000 fungal species, only 300 have been linked to disease in animals - Fungi are the most common plant pathogens • Human mycoses are caused by true fungal pathogens and opportunistic pathogens (a disease caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease) * True or primary fungal pathogen can invade and grow in a healthy, noncompromised host --> Most striking adaptation to survival and growth in the human host is the ability to switch from hyphal cells to yeast cells * Thermal dimorphism – grow as molds at 30°C and as yeasts at 37°C - Thermal Dimorphism: (1) When fungal spores from the environment gain entrance to a warm-blooded animal, they germinate into yeasts and remain in this phase in the host (2) Yeast cells leaving the animal host return to the environment and revert to the sporulating hyphae state --> these conversions can be demonstrated on artificial media in the laboratory -Healthy people generally resistant to most fungal infection (Skin and mucus membranes) –> Tissue temperature- majority grow better at less than 37C – Redox potential in vivo • Majority of fungal disease acquired from respiratory tract • Portal of entry – Primary mycoses – respiratory portal; inhaled spores – Subcutaneous – inoculated skin; trauma – Cutaneous and superficial – contamination of skin surfac • Virulence factors – thermal dimorphism, toxin-like substances, capsules and adhesion factors, hydrolytic enzymes, inflammatory stimulants * Most fungal pathogens do not require a host to complete their life cycles and infections are not communicable * Dermaphytes and Candida sp naturally inhabit human body and are transmissible * Dermaphytoses most prevalent * Cases go undiagnosed or misdiagnosed * True fungal pathogens are distributed in a predictable geographical pattern – climate, soil

Answer 11

• Restricted to endemic regions of the world, Infection occurs when matter containing conidia is disturbed, Spores germinate in the lungs, Infection can become systemic, Spores may be inoculated into the skin, All diseases result in immunity • Coccidioides immitis – causes coccidioidomycosis – most virulent of fungal pathogens • Distinctive morphology – blocklike arthroconidia in the free-living stage and spherules containing endospores in the lungs, Lives in alkaline soils in semiarid, hot climates and is endemic to southwestern U.S. • Arthrospores inhaled from dust, creates spherules, and can form nodules in the lungs --> Most people get mild disease that clears up completely, but some people appear to be genetically predisposed to a more serious systemic form of infection (5/1000 people) 1) Digging soil produces aerosol of arthrospores (inset) 2) inhaled arthrospores establish a lung infection 3) An arthrospore develops into a spherule that produces endospore --> endospores are released in the lungs 4) Immunocompetent persons effectively fight infection and return to health 5) Compromised people can develop meningitis, osteomyelitis, and skin granulomas - Patient present’s with: Fungal Pneumonia, Lung Nodules/Abcess, Disseminated skin manifestations - Risk factors: age, sex, immunosuppression -Histoplasma capsulatum –> most common true pathogen; causes histoplasmosis • Grows in moist soil high in nitrogen content • Inhaled conidia produce primary pulmonary infection that may progress to systemic involvement of a variety of organs and chronic lung disease • characterized by intracellular growth of the pathogen within macrophages and a granulomatous reaction in tissue -Soil with bird droppings is whipped by the wind --> microconidia are inhaled --> the patient develops mild pneumonitis which may recur --> in tissue phase, yeast phase develops, is phagocytosed, and mutliplies by budding intracellularly - most patients recover without compliance --> In some cases, phagocytes enter in the blood and can cause disseminated disease in a number of organs

Answer 12

-Blastomyces dermatitidis – causes blastomycosis (Dimorphic - exists in environmental form and host-associated form) --> Free-living species distributed in soil of a large section of the midwestern and southeastern U.S. (host associated form and environmental form) -Inhaled 10-100 conidia convert to yeasts and multiply in lungs --> escapes phagocytosis by shedding surface antigen after infection • Initial symptoms include cough and fever • Dissemination throughout body including the skin, bones and nervous system (Often mistaken for tuberculosis) • Amphotericin B is the anti fungal medicine used to treat it -Ex. Cutaneous Blastomyces: Man gets gruesome fungal lesion after snipping pimple with dirty wood tools - Diagnosis: Microscopic thick walled yeast in tissue or mucus of patient -> KOH examination - examined the presence of yeast with single broad-based buds, double refractive walls, and multiple nuclei - -> Potassium hydroxide (KOH) solution is alkaline and has the ability to dissolve keratin that is scraped from the outer layer of the skin. As the KOH dissolves the material binding the skin cells (and other cells) together, any fungus present is released. This allows for the identification of organisms such as dermatophytes -Paracoccidioidomycosis: aka Paracoccidioides brasiliensis • Distributed in Central and South America --> Lung infection occurs through inhalation or inoculation of spores • Systemic disease is not common --> Majority of infections are self-limited -Protists: Algae are eukaryotic organisms, usually unicellular and colonial, that photosynthesize with chlorophyll α • Protozoa - unicellular eukaryotes that lack tissues and share similarities in cell structure, nutrition, life cycle, and biochemistry -Algae: • Photosynthetic organisms --> Microscopic forms are unicellular, colonial, filamentous • Macroscopic forms are colonial and multicellular – giant kelp • Contain chloroplasts with chlorophyll and other pigments • Have Cell wall (or pellicle) and may or may not have flagella • Most are free living in fresh and marine water (ex. plankton) • can be single cell organisms and colonial organisms • Provide basis of food web in most aquatic habitats • Produce large proportion of atmospheric O2 • Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms - Algae Classification: Classified according to types of pigments and cell wall --> used for cosmetics, food, and medical products - LOOK AT TABLE ON SLIDE 79 - Main threat of algae to humans - do not infect humans with one exception (Prototheca causes a skin infection). - Threat to health comes from toxins released: Red Tide (Harmful algal bloom - caused by dinoflagellate:Karenia brevis (produces saxotoxin which is a potent neurotoxin that plays a role in paralytic shellfish poisoning). - other species also form HABs

Answer 13

• Diverse group of 65,000 species, Vary in shape because they lack a cell wall; Most are unicellular; colonies are rare; Most are harmless, free-living in a moist habitat; Some are animal parasites and can be spread by insect vectors; All are heterotrophic – lack chloroplasts; Cytoplasm divided into ectoplasm and endoplasm; Feed by engulfing other microbes and organic matter -Have locomotor structures like flagella, cilia, or pseudopods -Exist as trophozoite - motile feeding stage -Many can enter into a dormant resting state when conditions are unfavorable for growth and feeding (ex. cyst) -All reproduce asexually - mitosis or multiple fission --> many also reproduce sexually by conjugation -Life cycle: Trophozoite: active feeding stage --> cell rounds up and loses motility --> early cyst wall formation (when there is a lack of nutrients) --> mature cyst (dormant, resting stage) --> cyst wall breaks open (when moisture is restored) --> trophozoite reactivated Ex. Mastigophora: has cell membrane, glycocalyx, pellicle, organelles, and flagella -Sarcodina: Amoeba - asexual reproduction by fission --> most are free-living and not infectious -Ciliophora: Most are free-lining and harmless -Apiconplexa: Entire group is parasitic - no means of motility - complex life cycles (includes water born pathogens) -Multicellular animals, organs for reproduction, digestion, movement, protection • Parasitize host tissues --> Have mouthparts for attachment to or digestion of host tissues • Most have well-developed sex organs that produce eggs and sperm (Fertilized eggs go through larval period in or out of host body) -Protozoan Pathogen • Parasitology: The study of eukaryotic parasites, protozoa, and helminths • Protozoa: Single-celled, animal-like microbes, most having some form of motility – Estimated 100,000 species, approximately 25 are important pathogens – Life cycles vary • Most propagate by simple asexual cell division of the active feeding cell (trophozoite) • Many undergo formation of a cyst • Others have a complex life cycle that includes asexual and sexual phases • Entamoeba histolytica and Amebiasis: Alternates between a large trophozoite, motile by means of pseudopods and a smaller nonmotile cyst • Trophozoite has a large nucleus and lacks most other organelles – nucleolus called karyosome -Humans are the primary hosts •Cysts are swallowed and arrive at the small intestine --> alkaline pH and digestive juices stimulate cysts to release 4 trophozoites • Mature trophozoites attach, multiply, actively move about and feed in large intestine • Asymptomatic in 90% of patients --> Amoeba may secrete enzymes that dissolve tissues and penetrate deeper layers of the mucosa • Causing dysentery, abdominal pain, fever, diarrhea, and weight loss • Carried by 10% of world population -Life-threatening manifestations are: hemorrhage, perforation, appendicitis, and tumorlike growths (aka amoebomas) • extraintesinal infections may invade liver and lung • Severe forms of disease result in 10% fatality rate -Amebic Infections of the Brain: Caused by Naegleria fowleri and Acanthamoeba • Ordinarily inhabit standing water • Primary acute meningoencephalitis is acquired through nasal contact with water or traumatic eye damage • Infiltration of brain is usually fatal • Rare • Small, pear-shaped * 4 anterior flagella and an undulating membrane * Exist only in trophozoite form * 3 infect humans: T. vaginalis, T. tenax, T. hominis Trichomonas vaginalis * Causes an STD called trichomoniasis (Reservoir is human urogenital tract) --> Strict parasite, cannot survive long outside of host * 50% of infected are asymptomatic * Female symptoms – foul-smelling, green-to-yellow discharge; vulvitis; cervicitis; urinary frequency and pain * Male symptoms – urethritis, thin, milky discharge, occasionally prostate infection * Metronidazole treatment for 1 week * Easily identified by microscopy as moving cells due to flagella • Pathogenic flagellate --> Unique symmetrical heart shape with concave ventral surface that acts like a suction cup • Cysts are small, compact, and multinucleate • Reservoirs include beavers, cattle, coyotes, cats, and humans • Cysts can survive for 2 months in environment • Cysts survive in cold water for weeks --> enter small intestine germinate, feed and multiply • Usually ingested with water and food – ID 10 to 100 cysts • Causes giardiasis – diarrhea • Diagnosis is difficult: organism is shed in feces intermittently • Resistant to chlorine • Treatment: quinacrine or metronidazole

Answer 14

-Viral envelope – Mostly animal viruses – Acquired when the virus leaves the host cell– Exposed proteins on the outside of the envelope, called spikes, are essential for attachment of the virus to the host cell -Functions of Capsid/Envelope: Protect the nucleic acid when the virus is outside of the host cell and also helps the virus bind to cell surface and assists the penetration of the viral DNA or RNA into a suitable host cell -Complex viruses: atypical viruses–> Poxviruses lack a typical capsid and are covered by a dense layer of lipoproteins – Some bacteriophages have a polyhedral nucleocapsid along with a helical tail and attachment fibers -Nucleic Acids: Viral genome – either DNA or RNA but never both --> Carries genes necessary to invade host cell and redirect cell’s activity to make new viruses • Number of genes varies for each type of virus – few to hundreds -DNA viruses: Usually double-stranded (ds) but may be single stranded (ss) --> circular or linear -RNA viruses: Usually single stranded, may be double stranded, may be segmented into separate RNA pieces – ssRNA genomes ready for immediate translation are POSITIVE-SENSE RNA – ssRNA genomes that must be converted into proper form are NEGATIVE-SENSE RNA - + vs - sense: RNA is read by the ribosome and translated into amino acids to make a protein. • RNA has a directionality (or orientation) in order for the translation to make sense. • + sense RNA genome is in correct orientation, ribosome translate to protein directly • - sense RNA genome must first be converted into + sense before translation can begin -Other stuff in viral capsids • Some viruses package enzymes essential to establish an infection in their capsid – Polymerases – DNA or RNA – Replicases – copy RNA • RNA dependent RNA polymerase – Reverse transcriptase – synthesis of DNA from RNA (AIDS virus) • Viruses can also pack host material

Answer 15

-Obligate intracellular parasite –> specific for host, but viruses found that infect all forms of life ( Been around a VERY long time) • Ultra microscopic • Do not independently fulfill the characteristics of life – Alive or not? • Genome can be either RNA or DNA (single-stranded or double-stranded) -Requires electron microscope -Viral Structure: Viruses bear no resemblance to cells --> Lack protein-synthesizing machinery • Viruses contain only the parts needed to invade and control a host cell -Capsids: Protein coats that enclose and protect the nucleic acids -capsomers: protein subunits that makeup the capsid – The capsid together with the nucleic acid is the NUCELOCAPSID – Some viruses have an external covering called an ENVELOPE; those lacking an envelope are NAKED -Two structural capsid types: helical or icosahedral • Helical capsid - continuous helix of capsomers forming a cylindrical nucleocapsid • Icosahedral capsid – 20-sided with 12 corners

Answer 16

* Viruses are the most common cause of acute infections --> Several billion viral infections per year * Some viruses have high mortality rates * Possible connection of viruses to chronic afflictions of unknown cause * Viruses are major participants in the earth’s ecosystem

Answer 17

- Persistent InfectionsL Cell harbors the virus and is not immediately lysed - Length of time varies --> several weeks to Yeats or host's lifetime --> several can periodically reactivate - chronic latent stage - Measles may be hidden in brain cells for years - Herpes: cold sores and genital herpes - Herpes zoster: chickenpox and shingles -Viral Damage: Some animal viruses enter the host cell and permanently alter its genetic material resulting in cancer – transformation of the cell • Transformed cells have an increased rate of growth, alterations in chromosomes, and the capacity to divide for indefinite time periods resulting in tumors • Mammalian viruses capable of initiating tumors are called oncoviruses – Papillomavirus – cervical cancer – Epstein-Barr virus – Burkitt’s lymphoma

Answer 18

-Main criteria: structure, chemical composition, and genetic makeup - Family name ends in -viridae (i.e.Herpesviridae) and Genus name ends in -virus (ex. Simplexvirus) -(Still common to use the English vernacular names: Herpes simplex virus I (HSV-I)) -Virus coincidentally collides with a susceptible host cell and adsorbs specifically to receptor sites on the membrane • Host range or tropism – Cell or tissue type capable of supporting viral growth – Hepatitis B – human liver cells – Poliovirus – primate intestinal and nerve cells – Rabies – various cells of many mammals -Flexible cell membrane is penetrated by the whole virus or its nucleic acid by –> Endocytosis – entire virus is engulfed and enclosed in a vacuole or vesicle called an endosome – Fusion – envelope merges directly with membrane resulting in nucleocapsid’s entry into cytoplasm -Varies depending on whether the virus is a DNA or RNA virus •DNA viruses generally are replicated and assembled in the nucleus •RNA viruses generally are replicated and assembled in the cytoplasm – Positive-sense RNA contain the message for translation – Negative-sense RNA must be converted into positive-sense message -Release: Assembled viruses leave the host cell in one of two ways: – Budding – exocytosis; nucleocapsid binds to membrane which pinches off and sheds the viruses gradually; cell is not immediately destroyed – Lysis – nonenveloped and complex viruses released when cell dies and ruptures • Virion – fully formed extracellular virus particle that is virulent and able to establish infection in a host Damage to host cell: Cytopathic effects - virus-induced damage to cells 1. Changes in size and shape 2. Cytoplasmic inclusion bodies – masses of virus particles – damaged cell organelles 3. Cells fuse to form multinucleated cells – syncytia 4. Cell lysis 5. Alter DNA (cancer viruses) 6. Transform cells into cancerous cells

Answer 19

-Bacteriophages – bacterial viruses (phages) • Most widely studied are those that infect Escherichia coli –complex structure with dsDNA • Multiplication goes through similar stages as animal viruses • Only the nucleic acid enters the cytoplasm - uncoating is not necessary • Release is a result of cell lysis induced by viral enzymes and accumulation of viruses - lytic cycle - Multiplication Cycle: Adsorption, penetration, duplication of components and replication of genetic material, assembly of new virions, maturation, lysis of weakened cell, release of viruses - REVIEW CHART ON PAGE 50 -Lysogeny: The Silent Virus Infection • Not all phages complete the lytic cycle --> Some DNA phages, called temperate phages, undergo adsorption and penetration but don’t replicate • The viral genome inserts into bacterial genome and becomes an inactive prophage –> the cell is not lysed • Prophage is retained and copied during normal cell division resulting in the transfer of temperate phage genome to all host cell progeny – lysogeny --> results in the spread of the virus without killing host cell • Induction can occur resulting in activation of lysogenic prophage followed by viral replication and cell lysis • Transduction - Often viruses carry extra DNA in addition to their genome, which may encode for genes that can alter the state of the bacterial cell • Phage genes in the bacterial chromosome can cause the production of toxins or enzymes that cause pathology – lysogenic conversion – Corynebacterium diphtheriae – Vibrio cholerae – Clostridium botulinum -Obligate intracellular parasites that require appropriate cells to replicate • Methods used: – Cell (tissue) cultures – cultured cells grow in sheets that support viral replication and permit observation for cytopathic effects – Bird embryos – incubating egg is an ideal system; virus is injected through the shell – Live animal inoculation – occasionally used when necessary

Answer 20

-Prions - misfolded proteins, contain no nucleic acid –> Extremely resistant to usual sterilization techniques –> Cause transmissible spongiform encephalopathies, which are fatal neurodegenerative diseases -Common in animals: Scrapie in sheep and goats; Bovine spongiform encephalopathies (BSE), a.k.a. mad cow disease; Wasting disease in elk; Humans –Creutzfeldt-Jakob Syndrome (CJS) • 3 distinct influenza virus types: A, B, C – Type A causes most infectionous –> Based on different ribonucleoprotein antigens • Enveloped, Negative-sense ssRNA • Virus attaches to, and multiplies in, the cells of the respiratory tract, Segments of RNA genome enter the nucleus, and Finished viruses are assembled and bud off the cell • Structure: 3 types of membrane proteins inserted in lipid bilayer: hemagglutinin (H), neuraminidase (N), & M2 ion channel protein. • The 8 ribonucleoprotein segments each contain viral ssRNA surrounded by nucleoprotein & associated with RNA transcriptase. – Genome of virus consists of 10 genes encoded on 8 separate RNA strands - Key to glycoproteins spikes: - H is the most important virulence factor - binds to host cells (15 subtypes) - N hydrolyzes mucus and assists viral budding and release (N) - -> Both glycoproteins frequently undergo genetic changes decreasing the effectiveness of the host immune response * *Binding sites used to anchor virus to host cell have a low rate for mutation (keep the rate of infectivity the same) but the site of antibody binding has the high rate of mutation - A constant mutation is antigenic drift: A gradual change in amino acid composition (minor change) - Antigenic shift: one of the genes or RNA strands is substituted with a gene or strand from another influenza virus from a different animal host (major changes that can lead to a new strain)

Answer 21

* Viruses are the most common cause of acute infections --> Several billion viral infections per year * Some viruses have high mortality rates * Possible connection of viruses to chronic afflictions of unknown cause * Viruses are major participants in the earth’s ecosystem -Detection: take sample, infect cell culture to look for characteristic cytopathic effects, screen for parts of the virus, PCR, immunoflourescence or electron microscopy, screen for immune response to virus (antibodies) -Antiviral drugs can cause serious side effects – Target processes that overlap with host cell -Ex. AZT, a treatment for HIV targets nucleic acid synthesis • Antibiotics don’t work on viruses • Proactive vaccination to prevent infections

Answer 22

*Influenza A • Greatest virulence & epidemic spread --> Antigenic drift & shift -(reassortment of genes, occurs every few years) • 15 subtypes of H (humans 1, 2, 3) & 9 subtypes of N (1 & 2) *Influenza B • Only undergoes antigenic drift --> Not known to undergo antigenic shift (antigenically stable) --> Localized outbreaks • Only known to naturally infect humans *Influenza C • Known to cause only minor respiratory disease; probably not involved in epidemics • Relatively minor causes of disease, affecting humans & pigs • A: Acute, highly contagious respiratory illness • Seasonal, pandemics; among top 10 causes of death in U.S. – elderly & small children • Binds to ciliated cells of respiratory mucosa – Although receptors for H1N1 are dominant in upper part of respiratory tract, H5N1 receptors are found in lower portion of lung in humans • Causes rapid shedding of cells, stripping the respiratory epithelium --> severe inflammation --> Abrupt onset of Fever, headache, pharyngeal pain, shortness of breath, coughing -Weakened host defenses predispose patients to secondary bacterial infections (pneumonia) • DIAGNOSIS: – Rapid immunofluorescence tests to detect antigens in a pharyngeal specimen – serological testing to screen for antibody titer • Antiviral: Tamiflu • PREVENTION: Annual trivalent vaccine recommended – Intranasal vaccine attenuated vaccine --> (Flumist): discontinued – Injectable vaccine inactivated virus: trivalent or quadrivalent -Flu vaccine: Jan to May - FDA selects three strains that are then provided by CDC --> FDA distributes to manufacturers --> tests and licensure (Jun - Jul) --> Aug is filling and packaging --> Sep is release/shipping --> Oct to Nov: vaccination begins

Answer 23

-Hepatitis –inflammatory disease of liver cells that may result from several viruses (Functions of Liver: glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification • Interferes with liver’s excretion of bile pigments --> bilirubin accumulates in blood & tissues causing jaundice, a yellow tinge in skin & eyes • 3 principal viruses involved in hepatitis: – Hepatitis B (DNA virus), hepatitis A (RNA virus), hepatitis C (RNA virus) LOOK OVER CHART -Hepatitis A Virus: Cubical picornavirus relatively resistant to heat and acid --> Not carried chronically, principal reservoirs are asymptomatic, short-term carriers or people with clinical disease – Self-limiting infection • Fecal-oral transmission; multiplies in small intestine and enters the blood and is carried to the liver • Most infections subclinical or vague, flu-like symptoms occur; jaundice is seldom present • Prevention– Inactivated viral vaccine, Pooled immune serum globulin for those entering into endemic areas

Answer 24

-Enveloped DNA viruses– Hepatitis B virus (HBV) • Never been grown in tissue culture, Unusual genome containing both double- and single- stranded DNA • Reverse transcriptase, Dane particle – complete HBV virus particle that infects hepatocytes • Tropism for liver -Rabies: Rhabdovirus family (Genus Lyssavirus) • Enveloped, bullet-shaped virions, helical nucleocapsid (N), Negative-sense ssRNA genome, RNA-dependent RNA polymerase, Matrix (M) protein, Knob-like glycoprotein (G) • Slow, progressive zoonotic disease --> Primary reservoirs are wild mammals; it can be spread by both wild & domestic mammals by bites, scratches, & inhalation of droplets • Virus enters through bite, grows at trauma site for a week & multiplies, then enters nerve endings & advances toward ganglia, spinal cord & brain --> Infection cycle completed when virus replicates in salivary glands **Clinical phases of rabies: • Prodromal phase – fever, nausea, vomiting, headache, fatigue; some experience pain, burning, tingling sensations at site of wound • Furious phase – agitation, disorientation, seizures, twitching, hydrophobia • Dumb phase – paralyzed, disoriented, stuporous • Progress to coma phase, resulting in death

Answer 25

• Heterotroph – must obtain carbon in an organic form made by other living organisms such as proteins, carbohydrates, lipids, and nucleic acids • Autotroph – an organism that uses CO2, an inorganic gas as its carbon source – Not nutritionally dependent on other living things • Growth factors/essential nutrients are organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them • Growth factors must be provided as a nutrient – Essential amino acids, vitamins – Example: Humans can not synthesize 9 amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine – E.coli can make all 20 amino acids from simple building blocks • Main determinants of nutritional type are: – Carbon source – heterotroph, autotroph – Energy source • Chemotroph – gain energy from chemical compounds • Phototrophs – gain energy through photosynthesis

Answer 26

-Nutrition – process by which chemical substances (nutrients) are acquired from the environment and used in cellular activities -Essential nutrients – must be provided to an organism -Two categories of essential nutrients: – Macronutrients – required in large quantities; play principal roles in cell structure and metabolism • Proteins, carbohydrates – Micronutrients or trace elements – required in small amounts; involved in enzyme function and maintenance of protein structure • Manganese, zinc, nickel -• Organic nutrients – contain carbon and hydrogen atoms and are usually the products of living things – Methane (CH4), carbohydrates, lipids, proteins, and nucleic acids • Inorganic nutrients – atom or molecule that contains a combination of atoms other than carbon and hydrogen – Metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water ``` -E.coli: • 70% water • 96% of cell is composed of 6 elements: – Carbon – Hydrogen – Oxygen – Phosphorous – Sulfur – Nitrogen • 5000 different compounds, but only requires a few types of nutrients to synthesize everything it needs. – glucose, water, NaCl, FeCl2, (NH4)2, (SO4), KH2PO4, MgSO4, CaHPO4, trace elements ```

Answer 27

• Photoautotrophs– Photosynthesis for energy, CO2 for carbon source • Chemoautotrophs – energy from oxidation of organic or inorganic molecules, CO2 for carbon source – Methanogens, a kind of chemoautotroph • produce methane gas under anaerobic conditions • Majority are chemoheterotrophs – Aerobic respiration • Two categories – Saprobes: free-living microorganisms that feed on organic detritus from dead organisms • Opportunistic pathogen • Facultative parasite – Parasites: derive nutrients from host • Pathogens --> some are obligate parasites • Passive transport – does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration – Diffusion – Osmosis – diffusion of water – Facilitated diffusion – requires a carrier • Active transport – requires energy and carrier proteins; gradient independent – Active transport – Group translocation – transported molecule chemically altered – Bulk transport – endocytosis, exocytosis, pinocytosis - Diffusion – Net Movement of Molecules Down Their Concentration Gradient (Passive Transport) - Osmosis - Diffusion of Water (Passive Transport)

Answer 28

-Like the semipermeable bag --> Phospholipid bilayer that is selectively permeable – The barrier that defines the passage of nutrients into the cell and discharge of wastes – Water, CO2, O2, and some other small molecules can freely diffuse across the membrane. – Most other molecules need help - Hyper: Solutes greater outside cell - Iso: Solutes equal outside and inside - Hypo: Solutes lower outside that inside - Carrier-mediated: transport of solute dependent on solute binding to protein -> ATP is consumed - Group: molecule is chemically modified as it transits the membrane --> activation of sugar molecules for sue in the cell

Answer 29

• Niche: totality of adaptations organisms make to their habitat • Environmental factors affect the function of metabolic enzymes – Temperature – Oxygen requirements – pH – Osmotic pressure – Barometric pressure * Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism * Maximum temperature – highest temperature that permits a microbe’s growth and metabolism * Optimum temperature – promotes the fastest rate of growth and metabolism Psychrophiles – optimum temperature below 15 oC; capable of growth at 0 oC – Psychrotroph – Capable of growth below 7 oC, optimum growth above 20 oC Mesophiles – optimum temperature 20 o - 40 oC; most human pathogens -Thermophiles – optimum temperature greater than 45oC – Hyperthermophile – Optimum growth above 80 oC

Answer 30

• Biofilms: group of surface-associated microorganisms enclosed in an extracellular substance matrix --> Dominate the structure of most natural environments on earth • Quorum sensing – Bacterial communication with chemical messages that initiates a response as a function of population density • Enables bacteria to function as a group to accomplish tasks too big for an individual cell – release of toxin, digestion of food, synchronized fluorescence • Special chemicals that allow for inter and intra species communication among bacteria • Microbial growth occurs at two levels: growth at a cellular level with increase in size, and increase in population • Division of bacterial cells occurs mainly through binary fission (transverse) – Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells * Time required for a complete fission cycle is called the generation, or doubling time --> Each new fission cycle increases the population by a factor of 2 – exponential growth * Generation times vary from minutes to days - Calculating population size over time: Nf = Ni x 2^n - Nƒ = total number of cells in the population - Ni = starting number of cells - Exponent n = number of generations - 2^n = number of cells in that generation -In laboratory studies, populations typically display a predictable pattern over time – growth curve -Stages in the normal growth curve: 1. Lag phase – “flat” period of adjustment, enlargement; little growth 2. Exponential growth phase – a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment 3. Stationary phase – rate of cell growth equals rate of cell death caused by depleted nutrients and O2, excretion of organic acids and pollutants 4. Death phase – as limiting factors intensify, cells die exponentially

Answer 31

-Symbiotic – two organisms live together in a close partnership – Obligate Mutualism – obligatory, dependent; both members benefit – Nonobligate Mutualism –both members benefit; can live independently – Commensalism – commensal member benefits, other member neither harmed nor benefited – Parasitism – parasite is dependent and benefits; host is harmed Non-symbiotic – organisms are free-living; relationships not required for survival • Synergism (syntrophy) – ‘cross feeding’; members cooperate to produce a result that none of them could do alone • Antagonism (amensalism) – actions of one organism affect the success or survival of others in the same community (competition) -Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa - normal microbial flora – # of microbes associated with the body = to number of human cells of the body – Huge affect on our physiology, immunity and genetics – Most are not harmful within their niche, but can become opportunistic pathogens and cause infections • Commensal, parasitic, and synergistic relationships

Answer 32

-As oxygen is utilized, it is transformed into several toxic products: – Singlet oxygen (1O2), superoxide ion (O2), peroxide (H2O2), and hydroxylradicals (OH-) • Most cells have developed enzymes that neutralize these chemicals: --> Superoxide dismutase, catalase, oxidase ****If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats**** -Aerobe – utilizes oxygen and can detoxify it – Obligate aerobe – cannot grow without oxygen – Facultative anaerobe – utilizes oxygen but can also grow in its absence (capable but not restricted to particular function) • Aerobe – utilizes oxygen and can detoxify it – Obligate aerobe – cannot grow without oxygen – Facultative anaerobe – utilizes oxygen but can also grow in its absence – Microaerophilic – requires only a small amount of oxygen • Anaerobe – does not utilize oxygen – Obligate anaerobe – lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment – Aerotolerant anaerobes – do not utilize oxygen but can survive and grow in its presence --Effects of pH: • Majority of microorganisms grow at a pH between 6 and 8 (neutrophiles) • Acidophiles – grow at extreme acid pH • Alkalinophiles – grow at extreme alkaline pH *Osmotic Pressure: Most microbes exist under hypotonic or isotonic conditions • Halophiles – require a high concentration of salt • Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs *Other Environmental Factors • Barophiles – can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure

Answer 33

-Take diluted sampled and spread over solidified medium --> incubate plates and count colonies --> measure total estimated population in flask -Turbidometry – most simple (Degree of cloudiness, turbidity, reflects the relative population size) • Enumeration of bacteria: – Viable colony count – Direct cell count – count all cells present; automated or manual • cytometer

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