Question 1

Which of the following best explains the 'Great Plate Count Anomaly' observed in microbial ecology?

Accepted Answer

The number of microorganisms detected by direct microscopic counts is much higher than the number that can be cultured on laboratory plates.

Question 2

A researcher is interested in isolating a bacterium capable of nitrogen fixation from soil. Which cultivation strategy would be most appropriate?

Accepted Answer

Enrichment culture using a medium with mannitol as the carbon source and N$$_2 as $$the sole nitrogen source under anaerobic conditions.

Question 3

Which of the following is a limitation of cultivation-dependent methods in microbial ecology?

Accepted Answer

They may miss low-abundance species and organisms that do not grow on plates.

Question 4

In the sulfur cycle, which chemical form of sulfur is most likely to be found in oxic (oxygen-rich) environments?

Accepted Answer

Sulfate (SO$$_4$$^{2-}$$)

Question 5

A sample from an acid mine drainage site is found to contain high concentrations of Fe$$^{2+}. $$Which microbial process is most likely occurring?

Accepted Answer

Microbial oxidation of Fe$$^{2+} to Fe$^{3+}$$ under acidic, oxic conditions.

Question 6

Which of the following best describes the role of 16S rRNA gene sequencing in microbial ecology?

Accepted Answer

It serves as a molecular barcode for taxonomic identification of bacteria and archaea.

Question 7

Which of the following is a correct sequence of steps in the workflow for 16S rRNA gene sequencing?

Accepted Answer

DNA extraction $$\rightarrow$$ PCR amplification $$\rightarrow$$ Purification $$\rightarrow$$ Gel electrophoresis $$\rightarrow$$ Cycle sequencing $$\rightarrow$$ Database comparison

Question 8

Which of the following is a macronutrient required for microbial growth, and what is its usual environmental form?

Accepted Answer

Phosphorus (P); PO$$_4$$^{3-}$$

Question 9

A scientist wants to estimate the number of viable bacteria in a water sample. Which method would be most appropriate?

Accepted Answer

Most Probable Number (MPN) method using serial dilutions.

Question 10

Which of the following best describes the difference between pure culture and microbial community as used in laboratory studies?

Accepted Answer

A pure culture is a laboratory culture containing a single microbial species, while a microbial community contains multiple interacting species.

Question 11

Which of the following is a plausible explanation for why some microorganisms detected by molecular methods cannot be cultured in the laboratory?

Accepted Answer

They require specific growth conditions or nutrients not provided in standard laboratory media.

Question 12

In the context of the iron cycle, which of the following statements is correct regarding ferric iron (Fe$$^{3+}$$)?

Accepted Answer

It is reduced to ferrous iron (Fe$$^{2+}) in $$anoxic environments by microbial activity.

Question 13

Which of the following best describes the main advantage of using enrichment culture techniques in microbial ecology?

Accepted Answer

They select for microbes with specific metabolic traits by providing selective conditions.

Question 14

A researcher is studying sulfur-oxidizing bacteria in a marine environment. Which chemical form of sulfur would most likely serve as an electron donor for these bacteria?

Accepted Answer

Elemental sulfur (S$$^0)$$

Question 15

Which of the following is a key limitation of using 16S rRNA gene sequencing for microbial community analysis?

Accepted Answer

It cannot distinguish between closely related species due to conserved regions.

Question 16

Which of the following best describes the process of serial dilution and plating in microbial quantification?

Accepted Answer

It is used to isolate pure cultures and enumerate viable cells.

Question 17

Which of the following is a correct statement about the turnover time of sulfur in the atmosphere compared to the ocean?

Accepted Answer

Turnover time of sulfur in the atmosphere is much shorter than in the ocean.

Question 18

A scientist is using Koch's postulates to determine if a specific bacterium causes a disease. Which of the following is NOT one of Koch's postulates?

Accepted Answer

The organism must be the most abundant microbe in the environment.

Question 19

Which of the following best explains why the discrepancy in the Great Plate Count Anomaly is greater in oligotrophic environments?

Accepted Answer

Oligotrophic environments have low nutrient concentrations, so many microbes cannot be cultured using standard laboratory media.

Microbial Ecology: Cultivation Methods, Biogeochemical Cycles, and Microbial Nutrition

Guida di studio - Domande di pratica

Study guide - Flashcard