Viruses Animal 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 quite varied depending on type of viral nucleic acid synthesis and maturation 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 virus goes 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 disease Oncogenic 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 cells produced 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 Microbial Nutrition elements Nutrition and Growth 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 must be 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 amino acids 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 protozoa Metabolic Categories Nutritional Types based on how microorganisms obtain carbon and energy heterotrophs C comes from organic compounds use ready made organic molecules 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 some protozoa 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 of wastes 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 rapid dividing of cells physiologic tests are done when cells are in this phase stationary phase nutrients run out and cells cannot divide very 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 petriplate with 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 Influencing Growth nutrient limitation waste accumulation physical space other physical and chemical forces temperature enzymes effects rate of catalysis temp rate 2x per 10 C high temps will eventually degrade proteins too low and enzymes