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Using a back and forth mo"on to create confluent growthA dilu!on gradient is formed. The resul!ng gradient should always containwithin it the growth of individual colonies.Your Answer:5 / 5 ptsQues!on 23In what phase of a dilu"on streak would you expect to find the lowest concentra"onof bacteria, P2 or P4?P4 because when you get to zone 4 the bacteria has been thinned and diluted andthis is where you may find clonal isolatesP4 (Phase 4) would contain the lowest concentra!on of bacteria. The phasesrank (from highest to lowest), P1 > P2 > P3 > P4.2 / 2 ptsQues!on 24True or False. When performing a dilu"on streak a new (or sterilized) loop is notrequired for each phase as long as the bacterial culture is pure.True False Correct!Correct!A new or sterilized loop is absolutely required for each phase. Failure to do so would prevent the establishment of a dilu"on gradient, as the same bacterial concentra"on would be spread across both phase regions, regardless of whether or not the culture is pure.Your Answer:5 / 5 ptsQues!on 25The number of phases (3 vs. 4) and/or the number of "mes a loop passes through aprevious phase (once vs. mul"ple "mes) is acceptable provided what happens?Provided that it is documented and the resul"ng gradient holds the growth of theinvidual colonies, if not the experiement needs to be rerun. Either devia!on is acceptable in prac!ce provided the resul!ng gradientcontains within it the growth of individual colonies—if not, the experimentmust be repeated.2 / 2 ptsQues!on 26True or False. To restrict the growth of a pathogenic microbe a researcher mightdecrease an incubator from 37°C to 25°C.True Correct!Correct!Pathogenic strains of bacteria tend to grow faster than non-pathogenic strains at 37°C, so researchers may set incubators at 25°C to restrict its growth.False Your Answer:5 / 5 ptsQues!on 27When given an unknown bacterial sample the first step is to expand the currentbacterial popula"on. Which form of media best suites this need? Why?1. MSA agar2. LB media3. MacConkey agar4. Columbia CNA agarLB Media because it is a nutri"onally rich liquid and it is popular and frequently useddue to its ability to grow various different microbes.Correct AnswerLB media. All other op!ons (A, C and D) are all forms of selec!ve media,meaning they may poten!ally inhibit the growth of the unknown sample. Theculture should be first expanded and then place onto selec!ve/differen!alagar plates.0 / 2 ptsQues!on 28True or False. Only directly inges"ng the pre-formed clostridium toxin (neither thebacteria nor its spores) will cause disease in adults.True Correct AnswerCorrect AnswerFalse You Answered2 / 2 ptsQues!on 29True or False. There are currently no cures for tetanus.True Correct!Although the symptoms can be treated it is only to manage the discomfort not to cure.