MCB 3020L Final Exam Questions with Correct Answers
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Course
MCB 3020
Institution
MCB 3020
Importance of Handwashing - Answer-- Essential to the science of microbiology
•Rewind to 1846 / 174 (150) years ago / gold rush / potato famine era
•Dr. Ignaz Semmelweis and cadaverous particles
•But lets not forget his though process of childbed fever
•Sex, Body Position, Noise, Smell
...
MCB 3020L Final Exam Questions with
Correct Answers
Importance of Handwashing - Answer-- Essential to the science of microbiology
•Rewind to (150) years ago / gold rush / potato famine era
•Dr. Ignaz Semmelweis and cadaverous particles
•But lets not forget his though process of childbed fever
•Sex, Body Position, Noise, Smell
Aseptic Technique - Answer-- Set of routine measures that are taken to prevent
cultures, sterile media stocks, and other solutions from being contaminated by
unwanted organisms (sepsis)
- We use flames, gloves, EtOH, NaClO, UV, cabinets, autoclaves, and filters
** NO protection against bad techniques
Wet Mounts - Answer-- Non-heat fixed slides
- Used when you want to visualize living organisms
•Motility of bacteria (≥1000x)
•water samples for many kingdoms of life
•amoebas, paramecium, ciliates, arthropods, bacteria, protozoa, hydras, fungi,
phytoplankton, and algae
•Fluids (fecal, blood, semen, saliva)
•Pretty much any "wet" sample of interest ya know?
Why streak for isolation? - Answer-- Technique used to isolate a bacterial sample into
pure cultures
- only one phenotype/species
- Simultaneously diluting to obtain 1 colony forming unit of 1 cfu or 1 bacterial cell
•1 bacterial cell replicates by binary fission
•Same strain and very close to identical genomes.
•Slight spontaneous mutations still occur but not significant
Important things:
- Use a new loop for each quadrant
- Keep lid closed when not streaking
- Do not breathe onto the plate
- Optimal goal: many individual "circles" of bacteria
Quick Math Mindblower - Answer-•Many people don't really understand the scale of
bacterial mutations and how amazing spontaneous mutations that lead to resistance
are.
•BACTERIA ARE THE ULTIMATE COLONIZERS
•Lets take a nasty but serious example
, •E. coli k-12 has a 4.64 million base pair genome and a doubling time of 20 minutes
•Spontaneous mutation rate of 1 • 10-3 mutations per genome generation
•Roughly speaking, the chance for 1 perfect mutation at the perfect spot to confer strep
resistance in E. coli is 1 in 4.64 million
(actually lower bc not all nucleotides have same effect)
Antibiotics in Livestock - Answer-•Meaninggg the chance of a that mutation happening
are 1 in 4,640,000,000 divisions
•
•Sounds like not that likely but on average there can be 100,000,000 E. coli cells in a
gram of manure
•So in either 46 grams of manure or 2 hours, there will be a cell resistant to an antibiotic
•There is about 22680000 grams of manure per acre when fertilizing vegetable crops
•So there are about 500,000 E. coli cells ALREADY resistant to strep applied to each
crop!!!
•
•This happens SPONTANEOUSLY!!!!
•This is why we need to continue limiting giving antibiotics to farm animals (US vs UK vs
China)
•antibiotic use in livestock is likely to account for approximately 70-80 percent of total
consumption
Importance of Pipetting - Answer-•Why do we care?
•Good pipetting techniques are important to accomplish precise and accurate -
reproducible - results.
•We will use the micropipette in several of our subsequent experiments (PCR)
•Important!
•Please be aware that your pipettes are NOT cheap. Each pipette is about $500, so
please treat it carefully and don't contaminate them, break them or disassemble them.
Prevention of Cross Contamination - Answer-- Use a fresh tip each time
- Do not touch the well with the pipette, only with the tip
- If you suspect pipette contamination, wipe with ethanol on the outside. If the inside is
contaminated - talk to TA
- Draw up liquid slowly to prevent formation of aerosols
Gram Staining - Answer-- Needed to visualize bacteria
- Heat fix vs chemically fix
- Ingredients:
•Crystal Violet - Stains free peptidoglycan
•Iodine - Increases Affinity of CV to FP
•Decolorizer - Removes unbound CV, shrinks membranes
•Safranin - dyes all remaining membranes
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