VirusesAnimal Viruses-more varied replication cycles than bacteriophages-still have some basic stages-adsorption-very similar capsid (fibers) or envelope proteins (spikes)-penetration and uncoating -no injection structure-several methods:-endocytosis (enveloped and non enveloped)-membrane fusion (enveloped viruses)-translocation (direct penetration: few specific types of viruses)-uncoating: freeing of DNA or RNA of virus into the host cell-translocation: virus being threaded through the vesicle -synthesis and maturation-quite varied, depending on type of viral nucleic acid-release-several methods:-lysis-exocytosis (budding)Persistent Animal Viruses-persistent virus: causes long lasting infection (months, years, even decades)-chronic infection: long lasting but virus is always detectable -Hepatitis B, HIV-latent infection (latency): long lasting but virus is dormant (undetectable)-no symptoms (or they’re mild and ignored), no antibody production-Herpes viruses (simplex, zoster, Epstein-Barr)-Herpesviridae group-simplex: oral/genital herpes-zoster: chicken pox, shingles -first exposure leads to disease (initial infection- chicken pox), immune system kicks in to cure, the virusgoes into the spine and stays in sensory nerve roots and CNS for some decades and reactivates many decades later, making its way back to the skin (now called shingles) with much more severe symptoms -viruses remain inside host cells-host cell damage  diseaseOncogenic Viruses-cancer causing viruses-viral nucleic acid is incorporated into the host genome-can sit in the chromosome for years: messes up normal replication of cells or redirects how many times a cell goes through mitosis- the cellsproduced are damaged-redirect normal growth patterns of host cells-leads to neoplasia (cancer)-examples:-Burkitt’s lymphoma (Epstein-Barr virus)-some leukemias (retroviruses)-human papillomavirus (cervical cancer): recently discovered- cause minor damage to epithelial tissue (ex: warts) and can be sexually transmitted Other Infectious Particles-not really viruses but act similarly-prions-infectious protein particles (PrP): no nucleic acid-pathogens of animals-cause chronic persistent infections: neurologic diseases (usually of CNS)-slowly cause damage and eventually gets bad enough it causes symptoms-examples:-scrapies (sheep)-BSE (cattle): mad-cow disease -Creutzfelt-Jacob disease (humans)-Kuru (humans)-viroids-infectious RNA particles: no protein (no capsid around them)-pathogens of plant cells Nutrition and GrowthMicrobial Nutrition-elements-major bioelements (bulk elements): make up most weight-C, H, O, N, P, S-minor bioelements: tend to form ions (salts important for human function)-Ca, Na, Fe, Cl, K-micronutrients (trace minerals): tend to be metals -Cu, Mn, Zn- too high of levels of these can cause disease-molecules: elements come together to make these-organic biomolecules (molecules in living things with a C backbone)-types: proteins, carbohydrates, lipids, nucleic acids-many are macromolecules (cannot get across membrane)-synthesized from smaller inorganic or small organic molecules-growth factors (in human organisms: called vitamins)-organic molecules that cannot be synthesized and mustbe taken into the cell from the environment-how do microbes (no digestive systems) acquire nutrients?-transport across cell membrane -small inorganic and organic molecules (can get across membrane)-salts (ions), simple sugars (monosaccharides), aminoacids-carbon dioxide, oxygen, water-most bacteria and fungi, many protozoa -problem: some molecules in the environment are macromolecules (too large to get through cell wall and membrane- ex: big particles,proteins, complex carbs)-acquiring nutrients from large molecules-bacteria and fungi, some protozoa: secrete digestive (degradative) enzymes that break the macromolecule into smaller pieces (extracellular digestion)-phagocytosis and ingestion-some protozoaMetabolic Categories (Nutritional Types)-based on how microorganisms obtain carbon and energy-heterotrophs: C comes from organic compounds, use ready made organicmolecules for food (other feeders)-2 types:-chemoheterotrophs: get energy from organic compounds-predators: feed on living organisms-some protozoa (ciliates), few bacteria and fungi (very rare)-saprobes (saprophytic): live off dead or decaying organisms (decomposers)-most fungi (very common, many bacteria, someprotozoa-commensals: live on or in another organism, feeds off some organic materials the organism makes -bacteria, protozoa, fungi-parasites (pathogens): like commensals but damage/hurt the host organism as it lives on it-bacteria, fungi, protozoa, viruses -photoheterotrophs: get energy from light (very rare- ex: purple nonsulfur bacteria, green nonsulfur bacteria)-autotrophs: C comes from CO2, make own food from reducing CO2 (self-feeders)-2 types:-photoautotrophs: get energy from sunlight (ex: photosynthetic bacteria- cyanobacteria)-chemoautotrophs: get energy from inorganic compounds (ex: nitrifying bacteria)Bacterial Growth-microbiologists measure the growth of a population (how they reproduce)-types of growth;-open system: ideal conditions/system for growth and reproduction (unlimited nutrients, plenty of space for new cells, no build up ofwastes)-closed system: limited nutrients limited space, build up of wastes -standard/normal growth curve-lag phase: don’t seem to get many cells, amount of time for cells to take in nutrients-exponential growth phase (doubling growth): very rapiddividing of cells -physiologic tests are done when cells are in this phase-stationary phase: nutrients run out and cells cannot dividevery quickly so just as many cells are dying as are being produced-death phase: more cells are dying than are being produced-dashed line: how long the death phase goes on Methods of Enumeration (counting)-standard (viable) plate count: take sample and thinly spread on a petriplatewith growth medium and wait, look at colonies and count them, each colony represents one original cell (one of most common methods)-turbidity/spectrophotometric: (cloudiness), when some bacteria begin to divide they make the liquid cloudy, the cloudier the liquid, the more bacteria(spectrophotometer)-direct count (total cell count)-microscopy: take a drop out and put on a microscope slide and count the number of cells you see (slide with a grid printed on it- not used for counting large numbers of cells)-flow cytometry: mechanical way to count cells in a sample Factors