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Bio110 Exam 2:1
Growth Culture
| Define: sterile | Completely free of microbes |
|---|---|
| Define: aseptic technique | procedures that minimize unintentional introduction of microorganisms to media |
| Define: colony | pile of cells descended from a single cell |
| Define: psychrophiles | "cold loving" 0*C. True psychrophiles are sensitive to temperatures over 20*C, ideal = 15*C (rarely cause spoilage or disease) Psychrotrophs: optimum growth 20-30*C most low temp food spoilage |
| Define: mesophiles | "middle loving" MOST BACTERIA Most pathogens and spoilages 25-40*C is optimum Live inside animals |
| Define: thermophiles | "heat loving" 50-60*C cannot grow below 45*C sunlit soil, compost piles, hot springs Heat resistant endospores Extreme Thermophiles: 80*C or higher. Archaebacteria - volcanic and ocean vents |
| How do we use acidity | To preserve food (pickling) |
| Most bacteria like a pH of | 6.5-7.5, yeast and molds are 5-6 |
| Define: acidophiles | "acid loving" pH of 0.1-5.4 lactobacillus (lactic acid) |
| Define: alkaliphiles | "alkali loving" pH 7-12 Vibrio cholerae = 9 Soil bacterium Agrobacterium = 12 |
| Cells are ___% water | 80-90 |
| Define: halophiles | moderate to large salt concentrations (ocean water = 3.5% salt) Most in oceans Extreme/Obligate halophiles = HIGH salt (20-30%, dead sea or brine vats) Facultative = no high salt needed, but tolerate 2+% |
| Define: chemoheterotrophs | Obtain carbon from their energy source: lipids, proteins, carbs |
| Define: chemoautotrophs and photoautotrophs | obtain carbon from CO2 |
| Carbon makes up ___% of cell dry weight | 50 |
| Nitrogen makes up _____ | 14% of dry cell weight. Used for amino acids, DNA, RNA |
| Sulfur is used to Sources are | form proteins and vitamins Protein, Hydrogen sulfide, sulfates |
| Phosphorus is used to Sources are | Form DNA, RNA, ATP, and phospholipids inorganic phosphate salts/buffers |
| Define: obligate aerobes | require O2 to live Disadvantage: oxygen dissolves poorly in water |
| Define: facultative anerobes | can use oxygen, can grow in absence. complex enzymes. (E. coli, yeasts) |
| Define: obligate anerobes | Cannot use oxygen and are harmed by the presence of toxic forms of oxygen (Clostridium that causes tetanus and botulism) |
| Aerotolerant Anerobes | Can't use oxygen, but tolerate its presence. Can break down toxic forms of O2 (Lactobacillus) |
| Define: Microaerophiles | Require low concentrations of oxygen and sensitive to toxic forms of O2 (campylobacter) |
| Singlet Oxygen | extremely reactive O2 form, phagocytic cells |
| Superoxide Free Radicals (O2-) | Extremely toxic and reactive form of O2. All organisms growing in atmospheric oxygen must produce an enzyme superoxide dismutase (SOD) to get rid of them. SOD is made of facultative anerobes, aerotolerant anerobes, but NOT anerobes or microaerophiles |
| Reaction of O2- and SOD | O2- + O2- + 2H+ = = = > H2O2 + O2 SOD |
| Hydrogen Peroxide | toxic and active ingredient of antimicrobials (benzoyl peroxide) |
| What breaks down Hydrogen Peroxide | Catalase:breaks down hydrogen peroxide into water and O2. Common in humans Peroxidase: converts hydrogen peroxide into water |
| Define: culture medium and give requirements | nutrient material prepared for microbial growth in the lab. Must: be sterile, contain appropriate nutrients, be incubated at appropriate temp |
| Culture: | microbes that grow and multiply in or on a culture medium |
| When are special culture techniques used | for bacteria with unusual growth requirements (in animals, or CO2 levels like Capnophiles-high CO2 and low O2 |
| How can you produce CO2 rich environments? | Burn a candle in a jar with the specimens in the jar or use a gas generator with a petri plate/culture in a packet |
| Define: selective media | used to suppress the growth or unwanted bacteria and encourage the growth of desired microbes |
| Saboraud's Dextrose Agar: | pH of 5.6, discourages bacterial growth used on fungi |
| Brilliant green agar: | inhibits gram-positive bacteria, isolates gram-negative Salmonella |
| Bismuth Sulfite Agar: | used to isolate Salmonella typhi and inhibits growth of most other bacteria |
| Differential media | Used to distinguish colonies of a desired organism |
| Blood agar | used to distinguish bacter that destroy red blood cells (hemolysis) - clearing around colony (Streptococcus pyogenes) |
| Selective and differential media | both distinguish colonies and inhibit growth of other microbes |
| Mannitol Salt Agar: | distinguish select for staphylococcus aureus. The high salt discourages growth of other organisms. pH indicator changes color when mannitol is fermented to acid |
| MacConkey Agar: | distinguish and select for Salmonella. Bile salts and crystal violet discourage growth of gram-positive bacteria. Lactose plus Ph indicator: lactose fermenters produce pink/red colonies, nonfermenters are colorless |
| Enrichment culutre | doesn't suppress other growth, used for microbes with small numbers, used for fecal/soil samples helps increase ID chances |
| Steps (4) of binary fission | 1) cell elongates and DNA is replicated 2) Cell wall and plasma membrane begin to divide 3) cross-wall forms completely around divided DNA 4) cells separate |
| Bacterial growth is logarithmic | 2^n (1-2-8-16-32) |
| Lag phase of bacterial growth | Period or adjustment to new conditions little/no cell division intense metabolic activity 1 hr to several days |
| Log phase | Cells being to divide and generation time reaches a constant minimum Period of most rapid growth Cells are at highest metabolic activity Cells most susceptible to adverse environmental factors (radiation and antibiotics) |
| Stationary phase | Population size stabilizes overall cell number does not increase cell division begins to slow down Factors to slowing: accumulation of toxic waste materials, acidic pH of media, limited nutrients, insufficient oxygen supply |
| Death phase | cell number decreases at a logarithmic rate cells lost ability to divide few cells may remain population size decreases |
| Kinds of stock cultures | Frozen in glycerol/DMSO solution Lyophilized = freeze drying Agar slants Stabs Streak plates |
| Define/Describe Plate count | most frequent method for measuring bacterial populations Inoculate plate with sample and count colonies Assumptions: each colony originates from single cell, original inoculum is homogeneous, no cell aggregates are present |
| Advantages/Disadvantages of Plate count | + Measures viable cells - takes 24+ hours for colonies to be visible - Must be between 25 and 250 colonies to be accurate -Requires serial dilutions |
| Filtration | Used to measure small quantities of bacteria in a large sample volume. Filter is transferred to petri dish and incubated and count colonies |
| Most probable number (MPN) | Used to measure bacteria that won't grow on solid medium Dilute a sample repeatedly and incolutate several broth tubes for each dilution point Count number of + tubes in each set |
| Statistical method | Determines 95% probability that a bacterial population falls within a certain range |
| Direct microscopic count | specific volume of a bacterial suspension is placed on a microscope slide with a special grib. stain is added to visualize bacteria. cells are counted and multiplied by a factor to obtain conecntration. |
| Adavnatages/Disadvantages of Direct microscopic count | + no incubation time required - cannot always distinguish between live and dead bacteria - motile bacteria are hard to count - requires a high concentration of bacteria |
| Turbidity to measure | Spectrophotometer to determine % transmission or absorbance and multiply by a factor to find concentration |
| Advantages/disadvantages of turbidity | + no incubation time - cannot distinguish between live and dead - requires high concentration of bacteria |
| Metabolic activity to measure | Measure metabolic products (acids, CO2) VERY expensive |
| Dry weight to measure | bacteria/fungi in liquid media are centrifuged resulting cell pellet is weighed. Doesn't distinguish between live/dead cells |
| Biofilms | polysaccharide-encased bacterial communities attached to surfaces (slippery rocks, slime coatings, tarter on teach) Build resistance to chemicals (antibiotics, antimicrobial, disinfectants). 65% of human infections. CATHETERS! |
Created by:
je121
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