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Which of the following methods used to count microbes is correctly identified as direct or indirect?
- turbidity--direct method
- plate count--indirect measurement
-dry weight--direct measurement
-filtration--direct method
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Terms in this set (73)
Which of the following phases of the bacterial growth curve is matched with the correct definition?
- log phase--the phase in which organisms are actively dividing and the generation time is constant
-stationary phase--the phase in which cells are not dividing very rapidly as they acclimatize to a new environment
-lag phase--the phase in which the death of organisms exceeds the creation of new cells and the curve declines
-death phase--the phase in which the curve is flat; microbial deaths balance the number of new cells
A microbe reproduces by binary fission every 20 minutes under favorable conditions. If you started with one cell, how long would 10 generations take and how many bacteria would be present if all the conditions were just right?
-2 hours and 10 minutes, producing 1,048,576 bacteria
-24 hours, producing 262,144 bacteria
-3 hours 20 minutes, producing 1,024 bacteria
-18 hours and 40 minutes, producing 1 million bacteria
Which of the following statements accurately describes the culture medium necessary for growing Clostridium tetani?
-A chemically defined medium is one made up of extracts such as those from yeasts, meat, or plants whose exact chemical composition may vary slightly.
-Nutrient agar contains ingredients that combine with oxygen and remove it, creating an anaerobic environment.
-Reducing media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment.
-A complex medium is one whose exact chemical composition is known.
Application of heat to living cells can result in all of the following EXCEPT alteration of membrane permeability .decreased thermal death time. breaking of hydrogen bonds. damage to nucleic acids. denaturation of enzymesdenaturation of enzymesMicrobial control methods usually target any of the following microbial structures EXCEPT which one? -plasma membrane permeability -mitochondria -microbial proteins -nucleic acids-mitochondriaWhich of the following is the best method to sterilize heat-labile solutions? -dry heat -autoclave -freezing -membrane filtration -pasteurizationmembrane filtrationConsider various effects of moist and dry heat to control microbial growth. Which of the following methods would best reduce microbes without altering the taste and chemical composition of beer? -autoclaving -boiling -hot-air sterilization -pasteurizationpasteurizationWhich of the following disinfectants acts by disrupting the plasma membrane? heavy metals bisphenols soaps aldehydes halogensbisphenolsGluteraldehydes are among the most effective chemical control agents because they __________. -are oligodynamic -considered a relatively safe sterilizing agent -act as surfactants -are useful in preserving foodconsidered a relatively safe sterilizing agentSurface-active agents act by decreasing surface tension so that microbes can be more easily removed. All of the following agents use this mechanism of action EXCEPT __________. -quaternary ammonium compounds (quats) -halogens -acid-anionic sanitizers -soaps and detergents-halogensBiotechnology involves the -use of microorganisms to make desired products. -use of microorganisms to make desired products and the use of animal cells to make vaccines. -use of animal cells to make vaccines. -development of disease-resistant crop plants. -use of microorganisms to make desired products, the use of animal cells to make vaccines, and the development of disease-resistant crop plants.-use of microorganisms to make desired products, the use of animal cells to make vaccines, and the development of disease-resistant crop plants.Self-replicating DNA used to transmit a gene from one organism to another is a PCR. vector. clone. Southern blot. library.vector.PCR can be used to identify an unknown bacterium because -DNA can be electrophoresed. -DNA polymerase will replicate DNA. -all cells have RNA. -the RNA primer is specific. -all cells have DNA.-the RNA primer is specific.The use of an antibiotic-resistance gene on a plasmid used in genetic engineering makes -direct selection possible. -the recombinant cell unable to survive. -he recombinant cell dangerous. -replica plating possible. -All of the answers are correct.direct selection possibleWhy is baker's yeast useful for expressing genetically engineered genes? -Many inducible promoters from the yeast genome have been cloned, such as the lac operon. -The yeast cells do not secrete their protein products. -The yeast cells are best suited for making human products for medical use. -Yeast cells are eukaryotic and so would likely be successful in expressing eukaryotic genes.-Yeast cells are eukaryotic and so would likely be successful in expressing eukaryotic genes.The following are steps used to make DNA fingerprints. What is the third step? -Add stain. -Lyse cells. -Perform electrophoresis. -Collect DNA. -Digest with a restriction enzyme.Digest with a restriction enzyme.The Human Genome Project, which was completed in 2003, was focused on -determining the nucleotide sequence of the entire human genome. -finding a cure for all human genetic disorders. -determining all of the proteins encoded by the human genome. -identifying all of the genes in the human genome. -cloning all of the genes of the human genome.determining the nucleotide sequence of the entire human genome.Which statement regarding agricultural biotechnology is FALSE? -Scientists have used gene silencing to create tomatoes with a longer shelf life. -Scientists have created plants that are resistant to herbicides by using a mutant enzyme gene from Salmonella. -Scientists have created plants that produce an insect toxin originally found in bacteria. -Agricultural biotechnology is extremely limited because foreign genes cannot be inserted into plant cells.Agricultural biotechnology is extremely limited because foreign genes cannot be inserted into plant cells.Which of the following techniques is NOT used to introduce recombinant DNA into plants? -protoplast fusion -electroporation -Ti plasmids and Agrobacterium -gene guns -microinjectionmicroinjectionThe random shotgun method is used in -forensic microbiology. -RFLP analysis. -transforming plant cells with recombinant DNA. -amplification of unknown DNA. -genome sequencing.-genome sequencing.Which technique is often used to determine the identity and abundance of microorganisms in an environment? (This technique is particularly useful because it does not require culturing the organisms.) -nucleic acid hybridization -fluorescent in situ hybridization (FISH) -DNA chips -ribotypingfluorescent in situ hybridization (FISH)Organism A has 70 moles % G+C, and organism B has 40 moles % G+C. Which of the following can be concluded from these data? -The organisms make entirely different enzymes. -The two organisms are related. -The two organisms are unrelated. -Their nucleic acids will completely hybridize. -None of the answers is correct.The two organisms are unrelatedA clone is. -a taxon composed of species. -a genetically engineered cell. -a mound of cells on an agar medium. -genetically identical cells derived from a single cell. -None of the answers is correct.-genetically identical cells derived from a single cell.Organisms once classified as protists are now being divided into which of the following? -clades -strains -species -clonescladesThe highest level in the current taxonomic hierarchy is "Kingdom." -True -False-FalseIf two organisms have similar rRNA sequences, you can conclude that they -live in the same place. -will both ferment lactose. -will have different G-C ratios. -mated with each other. -evolved from a common ancestorevolved from a common ancestorWhich of the following statements about the members of the Kingdom Animalia is FALSE? -They ingest nutrients through a mouth. -They are composed of eukaryotic cells. -They are heterotrophs. -They are multicellular. -They undergo photosynthesis.-They undergo photosynthesis.Once a culture is purified, the next logical step in the process of identifying bacteria is biochemical testing. -True -false-falseWestern blotting is an immunological test used to identify the antibodies in the serum of an individual suspected of having Lyme disease. -True -FalseTrueThe Gram stain is not suitable for identifying members of the Archaea. -True -FalseFalseStreptomyces differs from Actinomyces because Streptomyces -is a strict aerobe. -makes antibiotics. -is a bacterium. -produces conidia. -forms filaments.-is a strict aerobe.Mycoplasmas differ from other bacteria in that they -are gram-negative. -grow inside host cells. -are acid-fast. -lack a cell wall. -are motile.lack a cell wall.Dengue fever is transmitted by which of the following? -sucking lice -fleas -mosquitoes -mites and ticksmosquitoesWhich of the following arthropods does NOT transmit diseases by sucking blood from a human host? -lice -fleas -houseflies -mosquitoes -kissing bugshousefliesHumans are the definitive host for __________, which is a type of __________. -Taenia solium; roundworm -Echinococcus granulosus; tapeworm -Plasmodium; cestode -Taenia saginata; tapeworm-Taenia saginata; tapewormThe Platyhelminthes group includes roundworms, tapeworms, and flukes. -true -false-falseThe encysted larva of the beef tapeworm is called a -proglottid. -cercaria. -redia. -metacercaria -cysticercus.-cysticercus.You see acid-fast oocysts in a fecal sample from a patient who has diarrhea. What is the MOST likely cause? -Taenia -Entamoeba -Giardia -Cryptosporidium -diatomsCryptosporidiumAll of the following are characteristic of algae EXCEPT which ONE of the following? -Some produce harmful toxins. -They are currently classified as plants. -They mostly live in aquatic habitats. -Most are photoautotrophs. -They may be unicellular or multicellular.-They are currently classified as plantsWhich of the following is a nucleated, unicellular organism that, if you changed the incubation temperature, would form filaments with conidiospores? -ascomycete -euglenozoa -cellular slime mold -plasmodial slime mold -tapewormascomyceteSeventeen patients in ten hospitals had cutaneous infections caused by Rhizopus. In all seventeen patients, Elastoplast bandages were placed over sterile gauze pads to cover wounds. Fourteen of the patients had surgical wounds, two had venous line insertion sites, and one had a bite wound. Lesions present when the bandages were removed ranged from vesiculopustular eruptions to ulcerations and skin necrosis requiring debridement. Fungi are more likely than bacteria to contaminate bandages because they -cannot tolerate high osmotic pressure. -can tolerate low-moisture conditions. -have a fermentative metabolism. -are aerobic. -prefer a neutral environment (pH 7).can tolerate low-moisture conditions.A viroid is a(n) -complete, infectious virus particle. -infectious piece of RNA without a capsid. -provirus. -capsid without nucleic acid. -infectious protein.-infectious piece of RNA without a capsid.Dogs do not get measles because their cells lack the correct receptor sites for that virus. -true -false-trueGlycoprotein spikes are found on the capsids of all viruses. -true -false-falseContinuous cell lines differ from primary cell lines in that -continuous cell lines can be maintained through an indefinite number of generations. -continuous cell lines always have to be re-isolated from animal tissues. -viruses can be grown in continuous cell lines. -continuous cell lines are derived from primary cell lines. -continuous cell lines are from human embryos.continuous cell lines can be maintained through an indefinite number of generations.Lysogeny can result in all of the following EXCEPT -immunity to reinfection by any phage. -specialized transduction. -immunity to reinfection by the same phage. -acquisition of new characteristics by the host cell. -phage conversion.-immunity to reinfection by any phage.A virus's ability to infect an animal cell depends primarily upon the -presence of receptor sites on the cell membrane. -type of viral nucleic acid. -enzymatic activity of a host cell. -presence of pili on the host cell wall. -host cell's ability to phagocytize viral particles.presence of receptor sites on the cell membrane.Which of the following places these items in the correct order for DNA-virus replication?1. Maturation2. DNA synthesis3. Transcription4. Translation 2; 3; 4; 1 4; 3; 2; 1 1; 2; 3; 4 4; 1; 2; 3 3; 4; 1; 22; 3; 4; 1Which one of the following steps does NOT occur during multiplication of a picornavirus? -synthesis of DNA -synthesis of viral proteins -synthesis of + strands of RNA -synthesis of - strands of RNA -None of the answers is correct.-synthesis of DNAWhich of the following is a human disease caused by prions? -subacute sclerosing panencephalitis (SSPE) -chickenpox (varicella) -shingles -Creutzfeldt-Jakob disease (CJD)Creutzfeldt-Jakob disease (CJD)Direct measurements-count microbial cellsPlate count Filtration Most probable number (MPN) method Direct microscopic countEnteropluri testRapid identification method One tube containing media for 15 biochemical tests is inoculated with an unknown enteric bacterium. After incubation, the tube is observed for results. The value for each positive test is circled, and the numbers from each group of tests are added to give the code number. Comparing the resultant code number with a computerized listing shows that the organism in the tube is Citrobacter freundii.slide agglutination testbacteria agglutinate when mixed with antibodies produced in response to the bacteriaEnzyme-linked immunosorbent assay (ELISA)Known antibodies and an unknown type of bacterium are added to a well; a reaction identifies the bacteria Turns a colorWestern blottingIdentifies antibodies in a patient's serum; confirms HIV infection Look for common shapes of antibody sequences that we used to fight HIV Problem: could be positive for HIV 6 months before you tested positive for this testPhage Typing Test for determining which phages a bacterium is susceptible toOn a plate, clearings called plaques appear where phages infect and lyse bacterial cellsFatty Acid ProfilesFAME: Fatty acid methyl esters provide profiles that are constant for a particular species $250,000Flow CytometryUses differences in electrical conductivity between species or fluorescenceHelminthsParasitic worms Two phyla: Platyhelminthes (flatworms) Do more damage Nematoda (roundworms) Physical damage; tissuesTrematodes (flukes)Flat, leaf-shaped Ventral and oral sucker Absorb food through cuticle covering Paragonimus spp.—lung fluke Schistosoma—blood flukeLife Cycle of helminthsDioecious Separate male and female Monoecious (hermaphroditic) Male and female reproductive systems in one animal Egg → larva(e) → adultCharacteristics of HelminthsMulticellular eukaryotic animals Specialized to live in hosts (host specific) May lack digestive system Reduced nervous system Reduced or lacking locomotion Complex reproductive systemCestodes (tapeworms)Scolex—head that has suckers for attachment Absorb food through cuticle Proglottids—body segments; contain male and female reproductive organs Humans as definitive hosts -Eggs from proglottids are ingested, hatch into larvae, and bore into the intestinal wall -Produce cysticerci -Taenia solium—pork tapeworm Humans as intermediate hosts -Eggs are ingested and hatch in the intestine -Larvae migrate to the liver or lungs and develop a hydatid cyst -Echinococcus granulosusNematodesRoundworms Cylindrical; complete digestive system Dioecious; males contain spicules Free-living and parasitic Eggs infective for humans Ascaris lumbricoides—infects human intestines Baylisascaris procyonis—raccoon roundworm Trichuris trichiura—whipworm Enterobius vermicularis—pinworm Itchy anusLarvae infective for humansStrongyloides—reemerging infection Can get once and can bio amplify in your body (auto infection) Necator americanus and Ancylostoma duodenale— hookworms; enter the skin and are carried to the intestines Dirofilaria immitis—spread by mosquitoes; causes heartwormMultiplication of Animal VirusesAttachment: viruses attach to the cell membrane Entry by receptor-mediated endocytosis or fusion Uncoating by viral or host enzymes Biosynthesis: production of nucleic acid and proteins Maturation: nucleic acid and capsid proteins assemble Release by budding (enveloped viruses) or rupture