Labs 7 and 8 Manual

Labs 7 and 8 Manual - WEEK 7 October 11 17 Control of Microbial Growth Exercises to be Completed Microbial Flora of the Hand Results Examin e your

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WEEK 7: October 11 - 17 Control of Microbial Growth Microbial Flora of the Hand Results Examine  your  streak  plate  from  your  hand  plate.  You  should  have  obtained  several  isolated   colonies,  all with  the  sam e  morphology  indicating  that  you  were  succ e s sful  in picking  an   isolated  colony  to begin  with. Show  your  streak  plate  to your  lab  instructor  who  will evaluate   your  technique. * * * Bacterial Conjugation Results Record  your  results  in the  table  below: Strain LB Media Result I - I ampicillin I streptomycin I ampicillin + streptomycin II - II ampicillin II streptomycin II ampicillin + streptomycin I + II ampicillin + streptomycin MCRO  251  Lab  Manual Exercises to be Completed   43
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Knowing that Strain I carries the gene for streptomycin resistance on the bacterial chromosome and that Strain II  carries the gene for ampicillin resistance on a plasmid; list all possible explanations for your observed results. * * * Microbial Flora of the Throat Materials (per  pair of students) 2 she e p  blood  agar  plates Procedure 1.  After  consulting  with your  lab  instructor,  select  an  isolated  colony,  and  streak  for isolated   colonies  on  the  she e p  blood  agar  plate,  heating  your  loop  between  quadrants. 2.   Rubber   band   your   two   plates   together   and   place   inverted   into   the   labeled   box   for   incubation. * * * Microbes in the Food Supply Procedure and Results : IMPORTANT!   Despite  the  fact that these  organism s  were  isolated  from  an  'approved'  food  source,  it   realize  that   on  the  agar  plates  they  are  now  present  in      extremely      high  numbers  and  must  be  treated       as  potential  pathogens ! 1. Examine  the  trypticase  soy  agar  plates  with the  dilutions  of alfalfa sprouts. 2.Using  the  dilution  that   most  nearly  results   in  30- 300  colonies  on   a   plate,   calculate  the   number  of organisms  per  gram  of food  sample  by  using: original sample  concentration   =  (# of colonies  counted/volume  plated)   x  (1/dilution counted) MCRO  251  Lab  Manual 44
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For example, 38 colonies from the 1:100 sample would be equal to 38  ÷  0.1 (which   equals 380) x [1/10 -2 ]. Remember: [1/10 -2 ] is equal to 1 x 10 2 ,   resulting in 3.8 x 10 bacteria/gram of  original sample.  3. Based on the instructions of your lab instructor, calculate the following: Organisms per gram of alfalfa sprout 4. Each pair should subculture a single, well-isolated colony of the type selected by your instructor into a trypticase  soy broth (to be used later in this lab session). 5. Record the colony description.
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This note was uploaded on 02/11/2012 for the course MCRO 251 taught by Professor Lorrainecramer during the Fall '09 term at UNC.

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Labs 7 and 8 Manual - WEEK 7 October 11 17 Control of Microbial Growth Exercises to be Completed Microbial Flora of the Hand Results Examin e your

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