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Microbiology
Chapter 6
| Question | Answer |
|---|---|
| What factors affect Microbial growth? | pH, water availability, O2, pH |
| How to asses microbial growth | calculating growth, growth curve, methods to measure growth |
| Microorganism based on their oxygen requirements for Growth | Aerobes, Obligate aerobes, anarobes (use fermentation), obligate anaerobes, Facultative anaerobes, Aerotolerant anaerobes, microaerophiles |
| What are the toxic products Oxygen can transform into? | O2, superoxide ion (O2-), peroxides (H2O2), and hydroxyls (OH-) *destroy cells and damage proteins Aerobic, facultative anaerobic organisms have these enzymes, but anaerobic organisms don't |
| Catalase test | positive reaction is the presence of bubbles(O2 present) |
| Obligate aerobes and Obligate anaerobes | *Obligate aerobes: Bacteria must grow with oxygen( psuedomonas) *Obligate anaerobes: Bacteria must grow without oxygen(closterdiun) |
| Microaerophiles | aerobes that require oxygen at low concentrations from 2 to 10% |
| Facultative anaerobes | can perform fermentation or anaerobic respiration or aerobic respiration (ex. E.coli) |
| Aerotolerant anaerobes | do not use aerobic metabolism but can tolerate its presence by having enzymes that detoxify oxygen’s poisonous forms |
| How does high & low temperature affect growth? | *Too high a temperature denatures proteins and cell membranes become too fluid (causing a lot of transport) *Too low a temperature results in rigid and fragile membranes(disturbs nutrient transport) |
| Taq Polymerase | An enzyme that replicates DNA |
| Psychrophiles | Organism that lives in the Arctic and Antarctic regions -5°C to 15°C |
| Psychrotrophs | 20°C to 30°C (ex: Bacillus) |
| Mesophiles | 25°C to 45°C (E.coli) |
| Thermophiles | 45°C to 70°C Hot springs |
| Hyperthermophiles | 70°C to 110°C Usually members of Archaea. ex) Hydrothermal vents |
| Neutrophiles: | bacteria and protozoa that grow best in a narrow range around neutral pH (6.5-7.5) |
| Alkalinophiles: | live in alkaline soils and water up to pH 11.5 (ex: bacteria) |
| Acidophiles: | bacteria and fungi that grow best in acidic habitats |
| Facultative halophiles: | can tolerate high salt environments |
| Obligate halophiles: | bacteria that must have high salt for cell growth (up to 30% salt) (can be archae) *Halobacterium(a member domain of Archaea) |
| Barophiles: | organisms that live under extreme pressure of water(members of archae) |
| Inoculum | Cells you introduced to medium(broth or solid) |
| Pure culture | All genetically identical |
| Colony: | formed from a single cell that undergoes many cell divisions |
| Streak-plate method | Cells from high conc. to low conc. *objective to reduce number of cells in spread |
| Disadvantages of Pour plate method | Difficult to get culture because they're embedded into agar |
| Types of culture media | Defined media, Complex media, Selective media,Differential media, Anaerobic media |
| Defined media: | exact chemical composition is known and each batch is chemically identical, easy to replicate |
| Deferential complex media | Made of bile salts extracted from natural products, which means concentrations will always differ. Can differentiate between different medias |
| Selective medium: | selecting growth of some microbes and inhibiting growth of other microbes. *pH makes it selective |
| Blood agar | used as a differential medium, not selective media |
| Beta-hemolysis | Blood cells are completely destroyed because color is clear around bacterial growth in blood agar. |
| Alpha-hemolysis | Partial break down in RBC because red color is a slightly seen in blood agar |
| Gama-hemolysis | No break down of RBC because colonies rich in red color in blood agar |
| MacConkey agar | *selective and differential medium*Selective because its made of Bile salt and crystal violet which inhibit growth of gram (+), Differential because Lactose+pH fermenters produce pink or purple colonies, nonfermenters are colorless. |
| Nutrient agar | not selective medium and not differential |
| TSA(triple soy agar) | non selective media |
| How do bacterial cells divide? | Binary Fission (1 cell replicated into 2 identical cells) |
| Doubling time/Generation time: | time required for parent cell to divide and produce two daughter cells |
| The growth curve in a bacterial culture | Lag phase, Log Phase, Stationary phase, Death phase |
| Lag phase | growth slow; cells adjusting, not multiplying at max. |
| Log Phase | exponential growth, max. rate of cell division |
| Stationary phase | cells stop growing/grow slowly; Due to low nutrients, or buildup of waste |
| Death phase | number of viable cells decreases(because we're only measuring live cells) |
| How to Measure Microbial Growth | Viable plate counts, Direct cell counts, Membrane filtration Turbidity method |
| Viable plate counts | Counting manually viable cells growing *limitation:need to have # of cells within that range, 30-300, depends on media used to get colonies |
| Direct cell count | does not distinguish between living and dead cells(measured by hemocytometer) *limitation: hard to evenly to get correct count,can't keep track if they're motile |
| what is Membrane filtration used for? | to estimate microbial population *limitation:depends on media, some might not grow. Size of membrane, some bacteria may pass through. *advantage: can determine the # of cells in a liquid |
| Turbidity Method | *measures with spectrophotometer, measures light transmitted through sample. *Limitation: must have high number of cells, contamination (finger prints on TT), ruptured cells cause more turbidity, not mixed well, cells clump&cannot separate |
| What organisms are based on source of carbon? | Autotrophs, heterotrophs, |
| Autotrophs | Use inorganic source of carbon (CO2) |
| Heterotroph | Catabolizes reduced organic molecules as source or carbon (rely on autotrophs) |
| What organisms based on use of chemical or light as source of energy? | chemotrophs, phototrophs |
| Chemotrophs | Obtain energy from redox rxn using inorganic and organic compounds |
| phototrophs | use light as their source of energy |
Created by:
izis
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