Chapter 6 – Microbiology Answers – Flashcards
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| Requirements for Growth |
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| Every organism has a range of suitable conditions it can live in; minimal, optimal, and maximum conditions. |
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| Psychrophiles |
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| -10 - 20 degrees Celsius |
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| Psychrotrophs |
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| 0-30 degrees Celsius; grow well at refrigerator temperature = food spoilage |
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| Mesophiles |
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| 10-50 degrees Celsius; refrigeration based off principle many pathogenic microbes don't grow very well outside of the 20-40 "Danger Zone" |
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| Thermophiles |
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| 40-70 degrees Celsius |
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| Hyperthermophiles |
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| 70-110 degrees Celsius |
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| Plasmolysis |
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| the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis |
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| halophiles |
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| extremophile organisms that thrive in environments with very high concentrations of salt |
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| Important elements for survival |
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| Nitrogen, Sulfur, Phosphorus |
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| Trace Elements |
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| Wide variety of locations, can be toxic in high amounts ex. Fe, Cu, Zn, Mg |
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| Oxygen |
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| Essential toxic and has toxic forms |
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| obligate aerobes |
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| oxygen required |
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| facultative anaerobe |
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| can grow with or without oxygen, but greater with oxygen |
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| obligate anaerobe |
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| only grows in the absence of oxygen |
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| aerotolerant anaerobes |
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| doesn't utilize oxygen but can grow in its' presence |
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| microaerophiles |
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| only grows in small concentrations of oxygen |
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| SOD |
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| superoxide dismutase detoxifies superoxide radicals/anions; converts them into oxygen (diatomic) and hydrogen peroxide |
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| Catalase |
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| detoxifies hydrogen peroxide, converts it into water and oxygen (diatomic); our cells have catalase |
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| peroxidase |
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| also detoxifies hydrogen peroxide, converts it into water only |
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| organic growth factors |
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| essential organic compounds an organism is unable to synthesize |
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| biofilms |
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| matrix made of DNA, polysaccharides, and proteins; cells communicate through film by quorum sensing. Biofilms make microbes more pathogenic, harder for drugs to penetrate film to reach cells. |
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| quorum sensing |
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| chemical communication |
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| culture medium |
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| nutrient material prepared for the growth of microorganisms |
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| inoculum |
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| microbes introduced into a media to initiate growth |
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| culture |
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| microbes that grow and multiply in or on a culture medium |
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| agar |
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| complex polysaccharide derived from marine algae |
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| chemically defined medium |
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| exact chemical composition is known |
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| complex media |
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| made up of nutrients including extracts from yeasts, meat, plants, or digests |
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| Complex media (liquid form) |
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| nutrient broth |
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| Complex media (nutrient broth + nutrient agar) |
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| nutrient agar |
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| growing anaerobes |
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| grown in a medium with chemicals that bind and use harmful oxygen or in a had where a candle or sack of CO2 and H2 deplete the oxygen |
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| Capnophiles |
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| microbes that grow well in high levels of CO2 |
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| Selective Media |
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| designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes |
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| Differential Media |
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| makes it easier to distinguish colonies of different microbes based one color changes in the media as a result of certain microbe by-products |
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| Enrichment Culture |
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| provides nutrients and environmental conditions that favor the growth of a particular microbe but not others; like selective but focus is to increase number of desired microbes. |
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| Biosafety Levels |
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| 1-basic microbiology teaching lab 2-open bench tops, gloves, lab coats, and possible eye masks required 3-for highly infectious airborne bacterial; uses safety cabinet, and negatively air pressurized filters for the lab room 4-only a few of these lab types in the US; lab is a sealed environment, under negative pressure, HEPA filters, personal wear space suits. |
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| colony |
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| theoretically arises from a single spore/microbe |
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| streak/plate method |
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| isolation technique |
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| preserving bacteria: Deep Freezing |
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| pure liquid culture is quick frozen; lasts several years |
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| preserving bacteria: Lyophilization |
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| freeze-drying; quick frozen and then water removed with vacuum, lasts several years. |
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| Generation time |
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| time required for a cell to divide |
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| Lag phase |
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| little to no cell division, 1 hr to several days; time for intense metabolic activity |
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| Log phase (exponential growth phase) |
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| cellular reproduction most productive, generation time is constant, most metabolic activity |
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| stationary phase |
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| period of equilibrium, number of microbe deaths balanced by newly formed microbes |
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| death phase |
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| nutrients used up/build up of by-products so number of deaths exceeds division; microbe population brought down to a sustainable size |
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| plate count (direct measurements of microbial growth) |
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| measures the number of viable cells; assumes each bacteria is a CFU; serial dilutions are used to decrease the number of CFUs to make the counting practical. |
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| pour plate (direct measurements of microbial growth) |
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| bacterial dilution mixed with agar before setting; can damage heat sensitive microbes and some will grow beneath surface, incubated, and CFU's counted |
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| spread plate (direct measurements of microbial growth) |
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| bacterial dilution spread onto the agar, incubated, and CFU's counted |
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| filtration (direct measurements of microbial growth) |
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| used to count number of bacteria in low concentration in a liquid |
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| MPN (direct measurements of microbial growth) |
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| most probable number; is only a statement that the bacterial population falls within a certain range based of statistics; based on there number of bacteria required for growth in a medium and bacterial solution concentrations |
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| direct microscopic count (direct measurements of microbial growth) |
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| bacterial suspension placed on microscope slide and microbes counts per volume |
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| turbidity (indirect measurement of microbial growth) |
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| bacteria in liquid medium have light |
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| metabolic activity (indirect measurement of microbial growth) |
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| measures amount of certain by-product to estimate amount of bacteria |
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| dry weight (indirect measurement of microbial growth) |
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| measure desiccated microbes |
