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