Exam 6: Microbial Growth

Figure 6.1 -In Figure 6.1, which line shows the growth of an obligate aerobe incubated anaerobically?

Most bacteria reproduce by

Most bacteria grow best at pH

An isolated colony on a streak plate contains millions or billions of identical cells.

In performing a ten- fold dilutions series from a sample containing 10,000 bacteria per milliliter, the fourth tube in the dilution series will have 10 cells per milliliter.

The addition of which of the following to a culture medium will neutralize acids?

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

Table 6.3 -Bacterial generation times for four different bacterial species were calculated in the media listed in Table 6.3. All media were prepared with tap water and incubated aerobically in the light. Compare and contrast the growth requirements of the four bacteria listed above. Which of the media, if any, are chemically defined?

Bacterial growth refers to an increase in the numbers of cells in a bacterial culture.

Assume you inoculated 100 cells into 100 ml of nutrient broth. You then inoculated 100 cells of the same species into 200 ml of nutrient broth. After incubation for 24 hours, you should have

Figure 6.1 -In Figure 6.1, which line best illustrates the growth of a facultative anaerobe incubated aerobically?

The biosafety level (BSL) for most introductory microbiology laboratories is

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

Turbidity is an indirect measurement of bacterial growth that can be measured using a spectrophotometer.

Filtration methods are used to count bacteria present in very low concentrations, such as in lakes and streams.

Nitrogen- fixing bacteria, such as cyanobacteria, can use atmospheric nitrogen (N₂) for their nitrogen source.

Figure 6.1 -In Figure 6.1 ,which line best depicts an obligate anaerobe in the presence of O₂?

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

Which enzyme catalyzes the reaction: H₂O₂ + 2H⁺ -2H₂O?

Thirty- six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate count. How many cells were in the original sample?