Question 1

Which technique is illustrated in the first image, showing a highly organized, multi-colored microbial community scraped from the human tongue, and what is its main advantage over traditional FISH?

Accepted Answer

CLASI-FISH (combinatorial labeling and spectral imaging–FISH); it enables simultaneous identification of over 100 species by unique spectral signatures.

Question 2

The second image shows a series of flasks and plates used to isolate a specific bacterium from soil. What is the principle behind this enrichment culture technique?

Accepted Answer

Using a selective medium that lacks a nutrient (e.g., NH$$_4^+) to $$select for bacteria capable of fixing N$$_2.$$

Question 3

The third image shows three Winogradsky columns with different colored layers. What do the colored layers represent?

Accepted Answer

Distinct microbial populations, such as purple sulfur bacteria, green sulfur bacteria, and cyanobacteria, each occupying specific redox zones.

Question 4

Which of the following best describes the purpose of the agar dilution tube method (as seen in the image with tubes containing embedded colonies)?

Accepted Answer

To isolate pure cultures of anaerobic bacteria by embedding them in agar and separating colonies spatially.

Question 5

The image of a pink-streaked agar plate with isolated colonies is most likely the result of which microbiological technique?

Accepted Answer

Streak plate method for isolating pure cultures.

Question 6

The image showing a robotic system pipetting into a microtiter plate is most closely associated with which modern microbiological method?

Accepted Answer

High-throughput culturing for isolating previously uncultured microorganisms.

Question 7

The image with green and red fluorescent cells is most likely showing the results of which technique, and what does it reveal?

Accepted Answer

Viability staining; green cells are alive and red cells are dead based on membrane integrity.

Question 8

The paired images of a grayscale field of round cells and a colored field with blue, yellow, and green cells demonstrate what key concept in microbial ecology?

Accepted Answer

Morphologically similar cells can be genetically diverse, as revealed by phylogenetic FISH.

Question 9

The image showing a microarray chip with many green and some red spots is most likely used for which type of analysis?

Accepted Answer

GeoChip functional gene microarray for detecting genes involved in biogeochemical cycles.

Question 10

Which image best illustrates the concept of enrichment bias, and what is the main cause of this bias?

Accepted Answer

The image showing different colony types after enrichment and plating; enrichment bias occurs because rapidly growing 'weed' species dominate under laboratory conditions, which may not reflect their abundance in nature.

Modern Methods for Measuring Microbial Communities and Activities

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