Question 1

Which of the following best describes the purpose of enrichment culture microbiology?

Accepted Answer

To select for desired organisms by manipulating medium and incubation conditions, favoring target organisms while inhibiting non-target organisms.

Question 2

In the Winogradsky column, which gradient is primarily responsible for the enrichment of purple sulfur bacteria in the lower mud layers?

Accepted Answer

H$$_2S $$concentration gradient

Question 3

Why does enrichment bias occur in laboratory cultures?

Accepted Answer

Because laboratory cultures contain higher nutrient concentrations than natural environments, favoring fast-growing but minor species.

Question 4

Which technique is used to estimate the number of microorganisms in a sample by serial dilution and observing growth?

Accepted Answer

Most-probable-number (MPN) technique

Question 5

A researcher wants to isolate slow-growing bacteria from a mixed culture. Which method would be most appropriate?

Accepted Answer

Laser tweezers

Question 6

What is the main advantage of using microfluidic devices for microbial cultivation?

Accepted Answer

They enable the confinement and growth of thousands of single cells in individual wells, reducing competition and favoring slow-growing species.

Question 7

Which fluorescent stain would you use to enumerate all microorganisms in a sample, regardless of viability?

Accepted Answer

DAPI, acridine orange (AO), or SYBR Green I

Question 8

What is the primary function of green fluorescent protein (GFP) in microbial studies?

Accepted Answer

To genetically engineer cells to autofluoresce, allowing tracking of live bacteria and bacterial processes.

Question 9

Fluorescence in situ hybridization (FISH) is most useful for:

Accepted Answer

Identifying and quantifying specific microbial species in the context of their communities using nucleic acid probes.

Question 10

Which omics approach would best reveal which genes are actively being expressed in a microbial community?

Accepted Answer

Metatranscriptomics

Question 11

Stable isotope probing (SIP) links metabolic activity to microbial diversity by:

Accepted Answer

Feeding the microbial community a stable isotope (e.g., $$^{13}C$$), then identifying organisms that incorporate it into their DNA.

Question 12

Which statement about the ability to isolate an organism from an environment is correct?

Accepted Answer

It demonstrates the presence of the organism in the habitat but says nothing about its ecological importance or abundance.

Question 13

In a most-probable-number (MPN) experiment, growth is observed in the $$10^{-4}$$ dilution but not in the $$10^{-5}$$ dilution. What is the minimum cell concentration in the original sample?

Accepted Answer

$$10^4$$ cells/ml

Question 14

Which of the following is a limitation of using DAPI, acridine orange, or SYBR Green I for microbial enumeration?

Accepted Answer

They cannot differentiate between live and dead cells.

Question 15

Which process results in fixed carbon being enriched in $$^{12}C $$and depleted in $$^{13}C $$relative to substrate CO$$_2$$?

Accepted Answer

CO$$_2$$ fixation by autotrophic organisms

Question 16

A researcher uses a microtiter plate to isolate Pelagibacter from seawater. What is the main benefit of this approach?

Accepted Answer

It enables the isolation of single cells in individual wells, reducing competition and favoring slow-growing, nutrient-poor adapted species.

Question 17

Which method would you use to sort cells by size, shape, or fluorescent properties in a fluid stream?

Accepted Answer

Flow cytometry

Question 18

What is the primary purpose of using viability stains in environmental samples?

Accepted Answer

To differentiate between live and dead cells based on membrane integrity.

Question 19

Which omics approach would best allow you to discover new genes and link them to phylotypes in a microbial community?

Accepted Answer

Metagenomics

Question 20

In a FISH experiment using multiple phylogenetic probes, what does a cell stained with two colors (e.g., turquoise, yellow, purple) indicate?

Accepted Answer

The cell reacted with two probes, indicating it shares phylogenetic characteristics with both targeted groups.

Measuring and Analyzing Microbial Systems: Culture-Dependent and Culture-Independent Methods

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