Microbiology

It is sometimes difficult to obtain pure cultures of microbes that grow naturally in mixed communities.

True

Microbes will only grow until the least represented (limiting) nutrient is used up.

True

Label the image with the statements that most accurately describe the process of plasmolysis.

1) Higher solute conc. outside the cell: water leaves the cell 2) Higher water conc. inside the cell; water leaves the cell

Match the statement to the correct step in the streak plate procedure.

1) start by sterilizing the loop 2) inoculate loop and streak back and forth in one area 3) sterilize loop and streak another area, passing over the previous section a few times 4) sterilize loop and streak the final area of the plate while passing over the previous area a few times

From which of the following would you be most likely to obtain a pure culture?

A single colony on a streak plate.

You use the streak-plate method to obtain a pure culture and observe individual colonies following incubation. Consider a single bacterial colony. All of the following statements about the colony are true EXCEPT:

All cells in the colony are expressing the same set of genes and are performing the same metabolic functions.

You observe bacteria growing on the surface of a Petri dish of nutrient agar you left on the counter in your lab. You can be confident that your bacteria are NOT which of the following?

Obligate anaerobes

When studying microbes, why is it important to separate mixed communities into individual pure cultures of the different species?

So we can understand the biochemical characteristics of one species without confusing it with another species.

You inoculate a flask containing a complex medium with a culture of bacteria and use a spectrophotometer to measure the absorbance of the culture to detect growth. Initial measurements show a modest turbidity (cloudiness) that remains unchanged for the first few hours, followed by a steady increase for the rest of the day. Why was there this delay in growth following inoculation?

The bacteria were actively expressing genes and synthesizing enzymes in order to grow in their new environment.

Identify the type of bacterial formation being shown in this image.

biofilm

Microorganisms that have complicated nutritional requirements are

fastidious

Choose the statement that best describes the concept behind the enrichment culture method.

the liquid culture enhances growth of only certain microbes, so this no increases in proportion with each transfer