Micro test chp 6-8
Supposed you stared a cultue fo E.Coli in the moringn and after lunch (4 hours) you calculate there are approximately 2^18 cells in your culture. How many generations have occured?
18 generations
The directon of DNA replication is always
5 to 3
Most bacterial grow between pH range of
6.5 to 7.5
Which concentration of ethanol is the most effective bactericide
70 percent
Which of the following are involved in translation?
A.ribosome, B. mRNA c.tRNA
Which of the following affects the elimination of bacteria form and object?
All of the above
In fig B in which tube are facultative anaerobes growing
B
False 2
Bacteria typically contain multiple chromosomes.
True
Bacterial populations die at a constant logarithmic rate
Which of the following pairs of terms is mismatched?
Bacteriostatic- kills vegatative bacterial cells
The addition of which of the following to a culture medium will neutralize?
Buffers
Fig C shows a typical bacterial growth curve with the x-axis indicating the log of the number of bacteria and the y-axis indicating time in culture. In the fig, which section shows a growth phase where the number of cells dying equals the number of cells dividing
C
False 3
Capnophiles are organisms that thrive in low levels of CO2
Which of the following are ways that microbes "fight back" against microbial control methods
Certain bacteria can use porins to regulated the entry of biocides.
In the semi-conservative replication of nucleic acids,base pairs are seldom mismatched because of the proof-reading capability of the
DNA polymerase
Which of the following statements is false
DNA replication proceeds in one direction around the bacterial chromosome.
Radiation
Damagage DNA via cross linkage
True 2
Dry heat destroys organisms by oxidation
In fig B, in which tube are microaerophiles growing?
E
Stationary phase
Equilibrium, the number of new cells= number of dead cells.
The term used to describe a segment of DNA that encodes a functional product is
Gene
Salts and sugars work to preserve foods by creating a
Hypertonic environment
Which of the following is a limitation of the autoclave?
It cannot be used with heat-labile materials
With reference to DNA replication what does "semi-conservative" mean?
It means the "new" DNA strand would be made from 1 of the original strands and 1 new strand of DNA
All of the following would be direct methods of measuring microbial growth except.
Measureing the metabolic activity of a culture( ie looking for a change in the color of the pH indicator in a culture)
Prions are one of the most difficult ( if not the most difficult) microbes to eradicate. However, there are methods confirmed to eliminate prion contaminants. Do any of the following describe an effective method?
Moist heat autoclave setting of 17 psi (134 degrees) with the additon fo NaOH for 60 mins.
Thinking back to oxygen tolerance and types of bacteria, which type of bacteria absolutely will not grow in the presence of oxygen?
Obligate anaerobes
Which of the following pairs is mismatched?
RNA polymerase- makes a molecule of RNA from a RNA template
What is the difference between transcription and translation?
Transcription makes mRNA from DNA and translation makes protein from mRNA
Think about the control of microbial growth. Select the true statement
When treating with antibiotics, the number/concentration of microbes is a factor that can affect the effcacy of the treatment.
False
When using the phrase"microbial growth" you are referring to an increase in the actual size of a bacterium, not the increase in bacterial number.
An enzyme in response to the presence of a substrate(product) is called
a repressibel enzyme
Patient with indwelling catheters are susceptible in infections because
biofilms develop on catheters
Heavy metals
broad activity against many antibiotic organisms by denaturing proteins.
Alcohols
denature proteins and dissolves lipids
An agent to reduce the number of bacteria on a toilet would most accurately be called a
disinfectant
Phenols
disrupts plasma membrane
Log phase
exponential increase in bacterial numbers
Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes?
freezing
Sanitization
high temperature washing to lower microbial counts
Lag phase
lots of activity preparing to divide
Which class of organisms thrives in moderated temps and thus comprised the majority of pathogenic organisms
mesophiles
Genetic change in bacteria can be brought about by
mutation conjugation transduction transformantion
These small circular pieces of DNA often encode genes for antibiotic resistance or toxin production
plasmid
Fredrick Griffith's experiment with S. pneumonia using mice resulted in the important observation that_________ of genes was possible by injecting both living nonencapuslated and heat-killed encapsulated bacteria into mice
recombination
Sterilization
removal of all microbial life
Degerming
removal of microbes from a limited area
Disinfection
removal of vegetative pathogens
Mannitol Salt agar is an example of
selective and differential media
Recall our discussion on the Lac operon model, for the synthesis of an inducible enzyme to occur, the following must happen
substrate must mind to the repressor to signal transcription
Which of the following is an example of a chemically-defined or simple media?
super duper media
During the translation process which of the following are involved in bringing the complimentary amino acid to the Ribosome?
tRNA
Give an example of a location/surface where a biofilm would be commonly found.
teeth, contact lenes
Conjugation differs form reproduction because conjucation
transfers DNA horizontally to cells in the same generation
There are a variety of mechanisms that enable the exchange of genetic information (DNA) within and between cells and increase microbial diversity. The mechanism by which entire sections of DNA are transferred(hop) from one region of a chromosome to another chromosomal region is called
transposons