Term
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Definition
-cell elongates and DNA is replicated
-cell wall and plasma membrane begin to constrict
-cross wall forms completely separating DNA
-cell separates |
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Term
| other ways bacteria can reproduce |
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Definition
-budding
-fragmenting or conidiospores |
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Term
| bacterium that reproduces by budding |
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Definition
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Term
| bacterium that fragments or forms conidiospores |
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Definition
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Term
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Definition
-very little change in cell number
-synthesis of enzymes and various molecules (cell adapt) |
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Term
| log (exponential growth) phase |
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Definition
-cell reproduction is most active
-general time is constant
-exponential increase in population |
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Term
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Definition
-growth rate slows
-cells dying = new cells
-due to exhaustion of nutrients, build up of waste, change in pH |
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Term
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Definition
-number of cells dying is greater than number of new cells
-population decreases exponentially |
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Term
| continuous flow culture allows... |
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Definition
| maintenance of a culture in a log phase |
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Term
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Definition
| time it takes for a population of bacteria to double in number |
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Term
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Definition
-diphasic growth that occurs when cells are growing on a mixture of 2 sugars
-cells grow using the fastest metabolizable sugar first (usually glucose)
-once it is exhausted there is a brief delay while enzymes needed to metabolize second sugar are synthesized |
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Term
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Definition
-a nutrient material prepared for growth of microorganisms
-can be liquid (broth) or solid 9tubes/petri dish) |
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Term
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Definition
| microorganisms initiated into a culture medium to initiate growth |
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Term
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Definition
| microorganisms that grow and multiply in or on a culture medium |
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Term
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Definition
-contain appropriate nutrients (source of E,C,N,S,P growth factors)
-have sufficient moisture
-pH appropriate
-suitable oxygen level
-be sterile
-be incubated at correct temp. |
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Term
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Definition
-contain appropriate nutrients (source of E,C,N,S,P growth factors)
-have sufficient moisture
-pH appropriate
-suitable oxygen level
-be sterile
-be incubated at correct temp. |
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Term
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Definition
| complex polysaccharide derived from algae |
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Term
| what makes agar good for microbio? |
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Definition
-not degraded(only a few microbes can)
-liquefies at 100 degrees celsius and remains liquid at temp above 40 celsius
-once solidified it remains solid up to temp of 100 degrees celsius |
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Term
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Definition
-chemically defined media
-complex media
-selective media
-differential media |
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Term
| chemically defined medium |
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Definition
-exact chemical composition is known
-glucose is often used as source of carbon and/or energy |
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Term
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Definition
-exact composition varies from batch to batch
-usually contains yeast, meat, plant, protein (peptones digests
-ECNS are provided by proteins
-yeast or meat extracts provide vitamins and other organic growth factors |
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Term
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Definition
-designed to suppress growth of certain microorganisms and promote growth of desired
-useful for isolation of specific organism in a mixed culture
-Sabouraud's dextrose agar
-EMB
-Bismuth sulfite agar |
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Term
| Sabouraud's dextrose agar |
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Definition
-used to identify fungi
-its pH of 5.6 prevents growth of most bacteria while allowing growth on fungi |
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Term
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Definition
-Eosin methylene blue
-selects for Gram negative
-E and M inhibit growth of Gram positive
-also differential
-turns green with lactic acid |
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Term
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Definition
-used to isolate Salmonella typhi
-bismuth sulfite inhibit Gram+and- |
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Term
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Definition
-allows to distinguish colonies of desired organisms from others growing on same plate
-uses biochemical characteristics or indicators
-Blood agar
-MacConkey agar |
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Term
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Definition
-contains RBCs
-used to identify bacterial species that destroy RBCs |
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Term
|
Definition
-used to identify bacteria that ferment lactose
-contains lactose and dye neutral red to stain bacteria forming lactose
-also selective
-bile salts and crystal violet inhibit Gram positive organisms |
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Term
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Definition
-contains 7.5% NaCl which inhibits most microorganisms except Staphylococcus
-also contains mannitol and pH indictator if mannitol is fermented |
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Term
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Definition
-usually liquid
-used to grow bacteria present in small numbers in a sample containing other microorganisms that may be present in large numbers
-selective for bacteria that need to be enriched
-MS medium |
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Term
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Definition
-magnesium chloride selenite
-used to enrich and isolate Salmonella from feces or other samples
-a small inoculum is used to inoculate MS broth
-after 48 hours, a small amount is transferred to a new tube of MS broth
-after 3-4 transfers, a small inoculum is plated onto a solid MS medium |
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Term
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Definition
-used to grow bacteria that cannot tolerate oxygen
-contains sodium thioglycolate (inactivates dissolved oxygen)
-heated just before to get rid of absorbed oxygen |
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Term
| types of direct measurement |
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Definition
-plate count (CFU)
-filtration
-most probable number method
-direct microscopic count |
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Term
| indirect measurement types |
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Definition
-turbidity
-metabolic activity
-dry weight |
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Term
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Definition
-measures number of viable cells
-takes some time for colonies to become visible
-assume that each cell divides to form a single colony (CFU)
-to be accurate plates need to contain 30-300 colonies
-serial dilutions must be performed |
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Term
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Definition
| number of colonies on plate x reciprocal of dilution |
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Term
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Definition
-inoculate empty plate
-add melted nutrient agar
-swirl
-colonies on and in solidified medium |
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Term
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Definition
-inoculate plate containing solid medium
-spread inoculum over surface evenly
-colonies grow on surface medium |
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Term
| pour plate vs spread plate |
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Definition
-pour plate is more accurate
-gives lower counts
-hot agar may kill some bacteria
-reduced growth rates of obligate anaerobes in depth of agar |
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Term
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Definition
-suitable for samples which there is a small amount of bacteria
-lakes, streams,
-at least 100ml of water passed through a filter with pores
-routinely used to detect coliform (fecal contamination) in water and food |
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Term
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Definition
-useful when organisms grown on solid medium
-statistical estimate-the greater the number of present bacteria in a sample, the more dilution is required to reduce the density to a point at which no bacteria are left to grow in the tubes containing the liquid medium |
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Term
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Definition
-a measure volume of a bacterial suspension is place on a microscope slide within a square centimeter area
-several fields are counted
-avg/volume = # bacteria/mL
-Petroff Hausser cell counter is specially designed for direct cell counting
-Coulter counters too |
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Term
| direct microscopic count problems |
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Definition
-motile bacteria hard to count
-some dead may be counted as living
-high cell concentration is needed
-but very rapid, no need for incubation |
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Term
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Definition
-based on the fact that bacteria multiply in a liquid medium and make it cloudy (turbid)
-spec is used
-beam of light transmitted through a bacterial suspension
-the more bacteria, the less the transmittance
-log scales indicates Abs
-abs can be matched with plate counts |
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Term
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Definition
-based on the assumption that the amount of metabolic product is proportional to the number of bacteria present
-Co2, acids... |
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Term
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Definition
-useful for filamentous bacteria and molds
-fungus or bacteria cultures filtered, dessicated (dried), weighted |
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