Microbiology Exam 2

Which of the following microbiology tools should be flame-sterilized until their metal glows orange-red hot right before use?

-inoculating loop -inoculating needle

The effectiveness of a microbial control agent depends on:

-number of microbes present -environment (organic matter, temperature, biofilms) -time of exposure -microbial growth

Figure 40 above is a growth curve for a purified bacterial strain, with time as the X axis and Optical Absorbance as the Y-axis. What is the generation time for these bacteria under these conditions?

21 minutes

In figure 38 above, what is the thermal death time?

60 minutes

Most bacteria grow best at pH _______, while most fungi grow best at pH _______.

7 & 5

Which concentration of ethanol is the most effective bactericide?

70 percent

A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample contained

94,000 cells per milliliter

Three cells with generation times of 60 minutes are inoculated into a culture medium. How many cells are there after 5 hours?

96

You have isolated a bacterium that grows in a medium containing only inorganic nutrients. Ammonia is oxidized by this bacterium to a nitrate ion. This bacterium

A chemoautotroph

In microbiology what is dichotomous key?

A graphic tool that offers a series of opposing choices that lead the user to the correct identification of a microorganism.

A holoenzyme is

An enzyme together with the cofactor(s) required for activity.

Which of the following statements regarding metabolism is False?

Anabolic reactions are degradative.

In Figure 32 above, which tube shows the expected growth pattern for a facultative anaerobe?

B

Figure 29 above shows a typical bacterial growth curve with the y-axis indicating the log of the number of bacteria and the x-axis indicating time in culture. In the figure, which sections of the graph illustrate a logarithmic change in cell membrane?

B and D

Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage, such as through the urethra and into urinary bladder) are susceptible to infections because

Biofilms can develop on catheters

In figure 29 above, which section (or sections) shows a growth phase where the number of cells dying equals the number of cells dividing?

C

The graph at the far left in Figure 14 above shows the reaction rate for an enzyme at its optimum temperature. Which graph shows enzyme activity at a higher temperature?

C

If there are two completely full containers of just-cooked hot rice of the same diameter, but container a) is 10 centimeters deep while container b) is 5 centimeters deep, which will likely allow growth (when in a refrigerator) of more Bacillus cereus spoilage bacteria?

Container a that is 5 centimeters deep.

An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n)

Disinfectant

In Figure 23 (above) of the electron transport chain, where is ADP + Pi —> ATP happening?

E

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

Facultative hapohiles

True/False: The use of enzymes by living cells is necessary to increase the activation energy threshold of a chemical reaction.

False

Salts and sugars work to preserve foods by creating a _________ that makes bacterial cells become plasmolyzed (their plasma membranes shrink away from their cell walls).

Hypertonic environment

How would a noncompetitive inhibitor interfere with the enzyme shown in Figure 12 above?

It would bind to B.

Most life on Earth depends on photosynthesis, if energy is traced back far enough. Does carbon "fixation" of CO2 into organic molecules like glucose happen in the light-dependent (light) reactions, or in the light-independent (dark) reactions called the Calvin cycle?

Light-independent (dark) reactions

Vaccine proteins can be freeze-dried as a method of microbial control and longer shelf-life, this is called:

Lyophilization

Biological __________ is removal of electrons or is dehydrogenation, while _______ is the gain of electrons or addition of hydrogen, and these reactions are usually paired.

Oxidation, reduction

Escherichia coli belongs to the

Proteobacteria

In Figure 23, the path labeled "2" is the flow of

Protons or hydrogen ions (H+)

Choose the correct order of terms from left to right (cold to hot as in figure 19) on preferred growth temperature:

Pyschrophiles, Pyschrotrophs, Mesophiles, Thermophiles, Hyperthermophiles

__________ is microbial contamination, while _______ is the absence of microbial contamination.

Sepsis, asepsis

Which of the following is the best definition of generation time?

The length of time needed for a cell to divide

True/False: Agar used as a solidifying agent in microbiological media since few bacteria can degrade it.

True

True/False: An isolated colony on a quadrant streak plates contains hundreds to millions of identical cells all arising from one initial cell.

True

True/False: Bacterial growth refers to an increase in the numbers of cells in a bacterial culture.

True

True/False: Both respiration and photosynthesis require the use of an electron transport chain.

True

True/False: Currently no members of Archaea have been linked to human disease.

True

True/False: Glycolysis is utilized by cells in both respiration and fermentation.

True

True/False: In general, ATP is generated in catabolic pathways and expended in anabolic pathways.

True

True/False: Once enzymes converts substrates into products, active sites revert back to original form.

True