Nutrients & Growth
What is the most important nutrient molecule for MO?
Carbon source
Gram+ won't grow only Gram-. Which type of media is used?
Selective media
One possibility to determine the # of living cells
- Petroff-Hauser chamber (but only if live-dead-strain is used!!!!!!)
- viable cell counting (colony forming units)
You want to sterile filter a buffer - what pore size do these membrane filters need to have
0.22 um
Why is a low pH in the environment a problem for most neutrophiles
Protons lead to protein denaturation
Why could sequencing of rRNA genes be helpful to establish protocols for cultivated "uncultured" bacteria?
Because you ay narrow down their taxonomy and be able to use protocols that have been established for closely related species.
The generation time is the shortest in __________
the exponential phase
Laboratory safety hoods have UV lights built in. What is the purpose of these UV lights?
UV light is absorbed by DNA and mutagenic, induces thymine-dimer formation --> DNA replication is affected --> survival of MO decreases
Phototrophs use ________ as energy source
light energy
You get a soil sample and want to search for antibiotic-producing bacteria. What would be the first step in the lab with your sample?
Obtaining a pure culture by serial dilution and a streak plate
You take an exponentially growing Pseudomonas aeruginosa culture (in TSM media, 37C) and dilute it into fresh media (TSB). You split it up into two tubes. One is continues to grow at 37 C, the other will be cultivated at 42 C. Which growth phase(s) will be affected?
Lag phase will be longer at higher temperatures
What is a good parameter to consider when you want to determine the efficacy of an antimicrobial?
decimal reduction time (D value)
Why does the color of E. coli and Salmonella colonies differ on Mac Conkey agar?
Bc of the differential nature of the media and its ability to distinguish lactose fermenters (E. coli) from non-fermenters (Salmonella)
Why does the color of E. coli and Salmonella colonies differ on Mac Conkey agar?
Bc of the differential nature of the media and its ability to distinguish lactose fermenters (E. coli) from non-fermenters (Salmonella)
You take an exponentially growing Pseudomonas aeruginosa culture (in TSM media, 37C) and dilute it into fresh media (TSB). You split it up into two tubes. One is continues to grow at 37 C, the other will be cultivated at 10 C. Which growth phase(s) will be affected?
lag phase, exponential phase, stationary phase
You wash your clothes in the washing machine - what type of eliminating microbes is the washing machine
Pasteurization
Hypochlorous acid, the active component of household bleach and one of the main antimicrobials produced during host defense, is a strong oxidant that oxidizes many cell components including amine acids (Cys, Arg, Met, His, Trp, Tyr), or nucleotides. You want to test the HOCl's efficacy to kill Escherichia albertii, a newly discovered pathogen. Which media would you use?
Defined media (not complex)
What is an advantage of using nutrient agar over nutrient broth
Cell is immobilized, will divide repeadedly and produce a colony (mound of clonal cells)
When preparing microbial media in the lab, why isn't it sufficient to simply boil the medium at 100 C for 15 min to sterilize it
endospores can tolerate 100 C
liquid would evaporate --> higher pressure results in 121 C / 250 F --sufficient
Clostridium botulinum is the cause of foodborne botulism and a obligate anaerobe which thrives in slightly acidic conditions. Why is it important for the commercial canning process to destroy the endospores of this species?
The spores could germinate in the can and cells become vegetative