Ch 6 – Microbiology – Flashcards
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| Requirements for microbial growth fall into these two categories? |
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| Physical and chemical |
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| What are the 3 physical requirements |
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| Temperature, pH, osmotic pressure |
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| Temperature requirements for.... Psychrophiles – |
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| Cold- food spoilage |
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| Temperature requirements for.... Mesophiles – |
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| moderate temp. 37 C= body temp |
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| Temperature requirements for.... Thermophiles – |
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| heat 50-60C |
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| Temperature requirements for.... Extreme thermophiles |
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| Very hot 80 up to 110C |
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| Name two extreme thermophiles |
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| Archea, sulrfur bacteria |
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| What is the most common type of bacteria as far as temperature requirements? |
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| Mesophiles (37 C/ body temp) |
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| What is the optimal pH range for most microbes? |
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| 6.5-7.5 |
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| Acidophiles= |
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| acidic pH, can tolerate to 1 |
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| Molds/Yeasts pH = |
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| 5-6 |
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| Most microbes= ______tonic conditions (hypo, hyper, iso) |
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| hyper |
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| Most microbes ___ to ___% water |
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| 80-90% |
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| Plasmolysis = |
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| plasma membrane shrinks away from the cell wall & interferes with metabolism |
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| Makes organic molecules= |
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| Carbon |
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| Second most important requirement for microbes |
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| Carbon |
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| Carbon is ___% of the dry weight of bacteria |
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| 50 |
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| Nitrogen is ___% of the dry weight of bacteria |
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| 14 |
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| Nitrogen is important for _______ |
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| protein synthesis |
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| Many microbes use N gas from atmosphere = |
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| nitrogen fixation |
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| Sulfur & Phosphorus = ___% dry weight of bacteria |
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| 4% |
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| Surfur (S) is important for? |
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| amino acid & vitamin synthesis |
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| Phosphorus is important for? |
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| ATP synthesis |
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| Trace elements (Fe++, Zn+, Cu++, etc.) are required in ____amounts. |
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| very small |
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| Obligate aerobes |
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| must have O2 |
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| Facultative aerobes |
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| Use O2 but grow w/o O2. +O2 use aerobic cellular respiration. -O2= switch to fermentation. |
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| Obligate anaerobes= |
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| unable to use O2. Can be toxic. Lack of enzymes to catabolize O2 (C. tetani & C. botulinum. |
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| Aerotolerant anaerobes+ |
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| Cannot use 02 for growth Can tolerate O2 presence. fermentation |
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| Microaerophiles |
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| O2 is required at lower levels than atmospheric O2 |
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| Culture Media= |
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| nutrient material for growth of microbes in vitro |
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| Inoculum= |
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| microbes introduced on culture medium |
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| Culture= |
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| organisms that grow on culture medium |
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| Sterile= |
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| initally contains no living organisms. |
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| Agar= |
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| complex polysaccharid, from marine algae, thickner in food (ice cream, jellies), culture media |
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| Why is Agar used as a culture media? |
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| not degraded by most bacteria liquid at 100C stays liquid at 100-40C |
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| Chemically defined medium |
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| exact chem. composition is known |
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| Complex medium |
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| exact chem. composition slightly varies from batch to batch |
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| liquid complex medium= |
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| nutrient broth |
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| solid complex medium= |
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| nutrient agar |
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| reducing medium= |
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| culture anaerobes "reduction" (GER); deplete O2 in medium |
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| Selective medium= |
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| suppress growth of unwanted bacteria and encourage growth of desired bacteria |
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| Differential medium |
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| selects a certain bacteria by chem reaction. Ex. blood agar plates= white halo around Steptococcus colonies. |
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| Enrichment culture |
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| Favors growth of one bacterium and not others. is a selective medium, but use low amount of bacteria to start ex. water sample |
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| Colony= |
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| visible growth on a plate many morphologies originate from one cell or one group of cells |
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| Preserving.. Deep Freezing- temp/how long |
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| -50 to -90C years |
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| Lyophilization= |
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| freeze drying, water removed -54 to -72C years solid water to vapor water use high vacuum |
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| most bacteria divide by_____ Some bacteria divide by |
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| binary fission budding (initial sep. from parent cell, bud, bud grows and separates (ex. yeast) |
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| Generation time= |
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| time required for cells to divide and population doubles |
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| generation time for most bacteria |
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| 1-3 hours |
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| each generation expressed as _______ |
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| exponent. ex. 8 cells, divide 7 times= 8 X 2 (to the 7th power)= 1024 graph on a logarithmic scale |
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| Bacteria growth curve is the growth of cells over _____. |
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| time |
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| 4 phases of bacteria growth |
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| Lag,log, stationary,death |
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| What is the phase of the most growth |
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| log |
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| lag= |
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| litte of no division, active metabolism, ex. new medium, 1 hr to days long |
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| log= |
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| highest metabolic rate highest susceptibility to drugs, radiation,etc. exponential growth phase |
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| stationary= |
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| decreased growth-nutrient exhausted, accumulation of waste, change pH slow metabolism |
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| death= |
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| log decline, few or no organisms left |
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| plate counts= |
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| measure # of viable bacteria minimum of 24 hours= disadvantage |
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| CFU= |
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| colony forming unity, can be one organism or one group of similar organisms. |
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| Each plate = ___ to ___ CFU |
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| 25 to 250 |
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| Serial dilutions |
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| dilute high bacterial counts quantitatively |
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| Serial dilutions if 10,000 bacteria. Dilute 1 ml to __ml liquid to create sample with 1000 bacteria |
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| 9 ml liquid |
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| 1,000 to start. Dilute 1 ml to ___ ml liquid to create sample = 100 bacteria |
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| 9 ml |
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| pour plate= |
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| a dilution placed in a dish and add liquid agar & mix |
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| Spread = |
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| dilution spread over surface of solid agar. use special spread stick. |
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| Filtration used to measure very ____ samples |
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| dilute. |
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| process for filtration 3-steps |
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| vacuum pulls medium through a filter bacteria caught on filter surface transfer filter onto agar surface |
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| MPN stands for what? one reason it would be used for measuring bacterial growth? |
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| most probable number for use with microbes that don't grow well in agar |
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| steps for mpn? |
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| Do many dilutions in multiple steps, count positive results, compare to special chart |
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| Direct microbial count= |
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| measured volume of bacterial suspension applied to a special microscope slide with grid. |
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| _____ bacteria are hard to count using direct microbial count method |
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| motile |
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| Coulter Counter= |
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| electronic counter used for direct microbial count. |
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| direct microbial count... each square represents a certain ______. Count the # of bacteria and multiply by the _____ _____ to get #/ml |
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| volume dilution factors |
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| Turbidity measures bacteria with a ________. _____numbers of bacteria causes the bacterial suspension to become increasingly _____ |
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| Spectophotometer, higher cloudy |
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| sensor in the spectophotmeter detects? |
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| light scatter |
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| One problem with using turbidity for measuring bacterial numbers of liquids with relatively small numbers of bacteria is _________ |
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| contaminants |
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| Metabolic activity estimates the number of bacteria by measuring the ____________ |
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| metabolic end products. ex. H2 gas production, pH |
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| What is the process involved for measuring bacteria using the dry weigh method? |
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| remove bacteria from medium, purified, dried in desiccator, weighed |
