Test Answers on Micro lab final – Flashcards
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| a nutrient agar plate that contains streptomycin is best described as what type of media? |
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| selective |
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| Missense |
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| mutation that causes a single nucleotide change, which then leads to a change in the amino acid sequence of a peptide |
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| if you innoculated a nutrient agar slant of Serratia marcescens and left it out over night on your bench, in the morning you would most likely see? |
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| red colonies |
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| 2 ways to determine the concentration of cells in a liquid culture |
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| serial dilution, spectrophotometer |
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| Why is it important to autoclave thioglycollate media before innoculating it with bacteria like Clostridium sporogenes? |
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| remove oxygen from media |
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| B. Stearothermophilus |
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| thermophile, extremophile |
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| when Pseudomona aeruginosa grows it may produce ? |
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| pyocyanin- a substance that inhibits bacterial growth |
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| in molds where would you expect to find most of the nutrient uptake occuring? |
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| hyphal tips |
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| 2 reasons why the human throat is an ideal environment for microbial growth to occur? |
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| mucus is a good media, turns over nutrients/waste, large aerobic surface area |
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| to determine the antibiotic ability of various chemicals relative to one another we looked for |
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| zones of inhibition |
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| liquid media |
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| nutrients suspended in liquid. Used to grow large numbers of microorganisms |
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| semisolid media |
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| solidifying agent added (agar). used for fermentation studies, bacterial motility and anaerobic growth. |
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| solid media |
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| solidifying agent added (agar) used for: surface growth of microorganisms in order to observe colony appearance, pure culture isolation, storage of cultures, observe specific reactions |
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| agar |
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| a polysaccharide composed of galactose obtained from raw seaweed. Agar dissolves |
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| agar |
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| a polysaccharide composed of galactose obtained from raw seaweed. Agar dissolves at 100 degrees C and solidifies at 42 degrees C |
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| agar slant |
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| liquid agar hardened at slanted position |
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| agar deep |
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| liquid agar hardened in upright position |
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| agar plate |
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| liquid agar poured into petri dish and allowed to harden |
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| chemically defined or synthetic media |
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| composed of known amounts of pure chemicals |
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| complex or nonsynthetic media |
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| composed of complex materials rich in vitamins and nutrients (beef extract, yeast extract, and peptone) |
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| sterilization |
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| process of rendering a medium or material free of all forms olf microorganisms |
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| autoclaving |
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| items are sterilized by exposure to steam at 121 degrees C and 15lbs of pressure for 15 minutes. |
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| microorganisms including endospores will not survive longer than about ___ minutes |
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| 12-13 |
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| is it high temp or pressure that kills microorganisms |
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| temp |
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| bacterial reproduction entails |
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| increase in cell size, duplication of entire chromosome, synthesis of new cell wall and plasma membrane and division (binary fission) |
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| 4 phases of exponential growth curve |
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| lag, log, stationary, death |
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| Lag phase |
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| freshly innoculated cells grow accustomed to their surroundings, needing to become accustomed to pH, salts, nutrients, oxygen levels, light, temperature. |
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| log (exponential phase) |
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| bacteria begin dividing on a fairly normal schedule(generation time) based on species and media. cell counts jump rapidly in a short period of time due to the doubling of the population. |
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| Stationary phase |
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| cells are at max growth potential, limited by nutrient concentration being too low, metabolic products which inhibit cell, space limitations (densely packed) . cell numbers remain same but not a static phase. cells are continuously growing up to a point and then stopping, population keeps moving |
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| death phase |
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| population of cells declines |
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| how do we count cell numbers? |
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| microscopic counts, electronic counts, viable counts (dilution series) |
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| how do we count cell mass? |
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| physical measures (weight, volume) chemical measures( atomic methods, protein/DNA counts) chemical activity measures(gas consumption/production) turbidity measures (optical density) |
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| turbidity |
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| term used for innoculated broth cultures with growth. (when there is growth the broth becomes cloudy or foggy, this can be given a quantitative number using UV spectroscopy. |
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| spectrophotometer |
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| measure an objects absorbance (AKA optical density) of light from source, as well as its transmittance of that light. |
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| spechtrophotometers have what issues? |
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| since dead cells refract as well, it is difficult to see the death phase and occasionally one will not appear at all, machines can be finicky, physics get in way, (limits to linear lines vs concentration) |
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| T or F? spectrophotometer readings are okay for quick estimations, they will not give you a physical number for the bacteria |
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| true |
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| viable counts |
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| use a broth culture which is serially diluted and plated on media to grow. the amount of colonies which grow are directly related to the amount of bacteria present in sample |
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| What gives the CFU |
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| colonies which grow in conjunction with the used dilution factor. |
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| T or F given viable counts we can accurately estimate the amount of bacteria in a culture. |
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| true |
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| Can you do a calculation of generation time with turbidity measurements? |
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| no, generation time requires you have a starting and ending CFU/mL. |
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| spread plating |
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| pouring a small amount of sample over an agar plate and spreading it along the surface until the agar absorbs the sample |
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| T or F serial dilutions will not always give good results, more often than not most of plates will be either too over grown with colonies or have extremely few |
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| true |
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| plates should be counted only if there are ______ well defined colonies |
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| 25-250 |
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| bacteriostatic agents |
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| inhibit microbial growth but do not kill the microbe (usually requires immune system) |
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| bacteriocidal agent |
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| kills bacteria provided concentration is high enough |
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| bacteriocidal agent |
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| kills bacteria provided concentration is high enough |
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| if no growth occurs on a plate with a reagent, restreak onto media with no reagent. if growth occurs? |
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| the agent was bacteriostatic |
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| if no growth occurs? |
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| agent was bacteriocidal (bacteria was killed/rendered nonviable |
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| zone of inhibition |
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| a halo which has formed around a disk which contains various chemicals due to the death or inhibition of bacterial cells. (bacteriocidal agents will also form zones of inhibition) |
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| antibiosis |
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| the harmful effect of one microorganism on another |
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| antibiotic |
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| a specific substance produced by a microorganism which exterts an inhibitory effect on certain other organisms |
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| streptomyces |
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| a group of gram + bacteria found in soil and decaying vegetation, most produce spores. distinct earthy odor which results from production of volatile metabolite, geosmin. make soil smell like soil |
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| streptomyces produce |
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| over 2/3 clinically useful antibiotics |
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| cyclohexamide |
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| inhibits growth of eukaryotic organisms and molds but not streptomyces, antibiotics can be isolated from soil with addition of cyclohexamide |
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| P. aeruginosa is known for? |
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| resistant to many antibiotics due to permeability barrier afforded by its outer membrane LPS. (natural habitat is soil, living in assoc. w bacilli actinomycetes and molds it has developed resistance to a variety of naturally occuring antibiotics) |
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| pyocyanin |
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| a blue pigment produced by some strains of P. aeruginosa, which can act as an antibiotic to other organisms (especially gram +) |
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| Wild type |
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| a naturally occuring strain of bacteria, typically seen when the cell is not stressed greatly |
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| mutant |
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| a bacterium which possesses a different genetic make up (genotype) This may or may not result in physical change of bacteria (phenotype) |
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| mutations can occur? |
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| by changing a single base pair of DNA, adding or removing large sequences. by changes in physical or chemical environment (UV light, heavy metals, xrays) |
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| point mutations |
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| single base pair changes |
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| silent mutations |
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| mutations where the base pair change does not alter the amino acid coded by that codon (CGA-CGG still gives an arginine) |
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| selective pressure |
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| can cause a mutant bacteria to gain dominance over its wild type |
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| missense mutation |
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| mutations which cause a change in the amino acid sequence ( AAA-AAC changes the amino acid from lysine to asparagine) |
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| nonsense mutations |
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| mutations which cause a codon to become a stop codon which can cause a shortening of the coded protein |
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| insertions/deletions |
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| mutations which add or remove segments of DNA. Results in shifting of reading frame which can change everything down the line. |
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| how can we select for mutants to appear |
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| altering conditions we put bacteria into. using selective media which forces bacteria to adapt or die. limiting nutrients, altering pH etc, addition of antibiotic, etc. |
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| frequency of mutation calculation |
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| # of mutant CFU's divided by inoculated CFU's. |
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| bacterial variation does not always mean a mutation has occured. Occasionally the environment can influence a gene or gene set ro produce a different level of expression (pigment production, motility, sporulation, toxin release, nutritional requirements) |
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| true |
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| Serratia marcescens produces a pigment with is partially dependant on temp |
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| true |
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| obligate anaerobes |
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| cannot grow in presence of oxygen at atmospheric levels. due to lack of enzyme which can protect them from oxygenic damage |
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| facultative anaerobes |
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| can use oxygen, but when none is present can also undergo anaerobic respiration/fermentation |
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| aerotolerant anaerobes |
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| can survive in presence of oxygen, but do not use it for their terminal electron acceptor |
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| to cultivate strict anaerobes |
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| oxygen needs to be removed from the media and surrounding area |
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| how is oxygen removed from media |
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| autoclaving, gas packet when mixed with water convert O2 to CO2 and H+ ions |
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| although some molds cause disease or food spoilage, some are useful for? |
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| biodegradation, production of various foods, beverages, antibiotics and enzymes |
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| molds secrete hydrolytic enzymes from predominantly the hyphal tips. these enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can enter the hyphae. |
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| in this way molds play a major role in decomposition of organic material. |
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| mycotoxins |
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| many molds secrete, together with hydrolytic enzymes, inhibit the growth of competing microorganisms. |
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| molds reproduce through |
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| small spores |
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| asexual mold spores |
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| the products of mitosis |
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| sexual mold spores |
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| products of meiosis |
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| mesophiles |
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| bacteria that live in moderate environments, akin to what we normally live in. |
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| extremophiles |
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| bacteria that live in harsh and extreme environments (like underwater hydrothermal vents) |
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| thermophile |
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| hot spring |
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| psychrophile |
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| glacier |
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| acidophile |
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| coal mine |
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| neutrophile |
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| pure water |
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| alkaliphile |
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| lime quarry |
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| halophile |
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| salt water |
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| osmophile |
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| sugar syrup |
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| Thermus aquaticus |
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| produces a highly heat resistant DNA polymerase which is now used in polymerase chain reactions (PCR)in labs. Taq polymerased |
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| - |
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| no growth |
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| + |
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| some minor growth |
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| ++ |
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| healthy, strong growth |
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| +++ |
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| overgrown culture |
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| yeast |
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| eukaryotic microorganisms classified in the kingdom Fungi |
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| yeast reproduce by |
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| asexually by budding, some by binary fission |
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| Saccharamyces cerevisiae |
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| used in baking and fermenting alcoholic beverages. model organism in modern cell biology research, most thoroughly researched eukaryotic organism |
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| opportunistic pathogens |
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| strike when opportunity like compromised immune system (candida albicans) |
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| sterile areas in body |
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| internal organs, blood vessels, cerebrospinal fluid, and urine |
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| bacteria which colonize our body are responsible for |
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| keeping potentially pathogenic strains from gaining a foothold in the body |
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| staphylococcus epidermidis/aureus |
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| found frequently on skin. if it gains access to open wound, staph infections can occur |
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| streptococcus pneumoniae |
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| present in upper respiratory tract of about half population. if it invades lower tract can cause pneumonia. causes 95% of all bacterial pneumonia |
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| some strains of E. coli cause |
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| intestinal infections, urinary tract infections, and neonatal meningitis |
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| Pseudomonas aeruginosa |
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| quintessential opportunistic pathogen of humans. invade virtually any tissue. leading cause of hospital acquired (nosocomal) gram-negative infections |
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| MRSA |
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| methicillin resistant staph aureus |
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| VRSA |
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| vancomycin resistant staph aureus/enterococcus |
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| nasal passage, throat and lungs |
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| provide a unique environment for microbial growth |
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| mucus |
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| excellent media, constantly turning over nutrients/waste |
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| respiratory tract |
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| largely aerobic, although large surface area contributes to small anoxic regions |
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| staphylococcus, streptococcus and neisseria are |
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| very common in respiratory tract |
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| media for skin flora |
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| blood agar, phenethyl alcohol agar plate |
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| media for resp flora |
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| blood agar, mannitol salt plate |
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| fermentation |
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| anaerobic catabolism of organic compounds in the absence of an external electron acceptor |
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| milk |
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| contains the disaccharide lactose that can be hydrolyzed by the enzyme lactase into glucose and galactose. |
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| glucose and galactose fermented to |
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| lactic acid |
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| peptonization |
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| process by which organisms produce proteo |
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| peptonization |
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| process by which organisms produce proteolytic enzymes to digest proteins into peptides (milk,casein is digested into peptones and amino acids) |
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| litmus |
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| a pH indicator that is purple to blue at neutral to alkaline pH and pink under acid conditions |
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| if lactose is fermented |
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| the solution should turn pink. |
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| if lactose is not fermented |
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| proteins are instead used for energy, the solution will become alkaline and more blue |
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| casein protein may be digested |
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| coagulating milk to form a curd |
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| casein may be metabolized all the way down to |
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| individual amino acids. this process is called peptonization, results in a clear(not milky) liquid that is usually brown in color. |
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| alpha hemolysis |
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| partial breakdown of blood cells. green tinge to develop around the colonies. |
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| beta hemolysis |
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| full lysis of blood cells, causing clear zone to appear around colony |
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| gamma hemolysis |
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| no hemolysis occurs |
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| on mannitol salt plates, looked for |
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| staphylococci (clusters of cocci) |
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| mycolic acids |
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| long chains of carbon fatty acids (60-90) give bacteria a waxy coating. makes it resistant to drying out, and nutrient uptake difficult and slow growth. |
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| Mycobacterium tuberculosis |
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| a bacteria which uses mycolic acids |
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| coliform bacteria |
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| gram - rods, ability to ferment lactose to an acid end product, along with gas. frequently found in the gut of warm blooded animal feces, easy to cultivate and usually non pathogenic |
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| total coliform |
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| entire coliform population, lactose fermentors |
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| fecal coliform |
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| sub section of total coliform that can grow in the presence of bile salts and at higher temps (44 degrees C) |
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| E. coli |
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| sub set of fecal coliform and best indicator of fecal contamination in drinking water, differentiated by further metabolic differences |
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| contamination can occur |
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| broken sewage pipe, large areas of pavement have excessive run off, dead animal carcasses, warm temp, high population, large amounts of rain |
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| potable water |
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| water which is free of detectable levels of coliform bacteria |
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| phenethyl alcohol agar |
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| inhibits (selects against) gram negative bacteria |
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| mannitol salts agar |
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| 7.5% NaCl and is therefore selective for halotolerant or halophillic bacteria |
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| positive mannitol fermentation |
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| yellow halo |
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| XLD (xylose lysine deoxycholate) agar |
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| selective against normal coliforms (E. coli and gram + bacteria) |
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| xylose fermentation |
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| yellow (non pathogens) |
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| H2S production |
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| black centers |
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| EMB (eosin Y-methylene blue) agar |
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| tests for lactose fermentation |
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| lactose fermentation |
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| green metallic (E. coli) or pink colonies |
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| TSI (triple sugar iron) agar |
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| glucose fermentation=red slant, yellow butt lactose/sucrose fermentation=yellow slant and butt gas production=split in agar H2S production=black |
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| CTA (cystine trypticase) agar |
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| tests for breakdown of carbs sugar fermentation = yellow |
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| urea broth |
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| test for presence of urease (breaks down urea) urease + = red (alkaline) |
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| normal flora of skin include |
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| yeasts and bacteria. yeasts primarily Pityrosporum |
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| staphylococcus epidermidis |
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| pathogenic on wounds, catheters and heart valves |
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| Micrococcus luteus |
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| relatively harmless |
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| Pityrosporum ovale |
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| responsible for dandruff when in large numbers |
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| propionobacterium acnes |
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| responsible for acne |
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| larger variety of flora of throat and nasal passages than of skin |
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| true |
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| normal flora of throat and nasal passages |
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| streptococcus, neisseria, haemophilus, anaerobic bacteriodes |
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| pathogenic species of flora of throat and nasal passages |
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| Staphylococcus aureus, corynebacterium diptheriae, neisseria meningitides, haemiophilus influenzae |
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| method of bacterial isolation and identification of nasal flora most commonly used |
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| blood agar |
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| blood agar |
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| distinctly seperates and identifies Streptococcus and Staphylococcus strains |
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| Streptococcus colonies appear |
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| small and translucent |
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| Staphylococcus colonies appear |
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| large and opaque |
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| media for skin |
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| EMB, TSI slant, CTA slants |
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| pneumococci sensitive to |
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| optochin |
