Question 1

Most methanotrophs are obligate ________ because ________.

Accepted Answer

Methane oxidation requires oxygen, which means that methanotrophs need to be aerobic in order to carry out this process.

Question 2

Nitrogenase is a critical enzyme in the nitrogen cycle because it catalyzes the

Accepted Answer

Nitrogenase is responsible for fixing atmospheric nitrogen gas (N2) into ammonia (NH3). This process is known as nitrogen fixation and is a critical step in the nitrogen cycle. The other options (assimilation of ammonia, dissimilative reduction of nitrate to nitrogen gas, and oxidation of nitrogen gas into nitrate) are all important processes in the nitrogen cycle but are not directly catalyzed by nitrogenase.

Question 3

Which of the following functional groups form symbiotic relationships with Eukaryotes in deep sea environments?

Accepted Answer

Both methanotrophs and sulfide-oxidizers can form symbiotic relationships with eukaryotes in deep sea environments. Methanotrophs can use methane as their energy source and provide nutrition to eukaryotes, while sulfide-oxidizers can use hydrogen sulfide and provide eukaryotes with nutrition and protection from toxic sulfide environments. Dissimilatory iron-oxidizers do not typically form symbiotic relationships with eukaryotes in deep sea environments.

Question 4

Bdellovibrio species are ________ cells that replicate in the ________.

Accepted Answer

Bdellovibrio species are predatory bacteria that replicate in the periplasmic space of other bacteria. They use flagella to locate and penetrate their host, then digest the host's contents to replicate themselves. They are not symbiotic, lithotrophic, or denitrifying, so options A, B, and D are incorrect.

Question 5

Green sulfur bacteria are often found at the greatest depths of all phototrophic cells in lakes, oceans, and microbial mats. This is because green sulfur bacteria

Accepted Answer

Green sulfur bacteria have chlorosomes that are very efficient at harvesting light, allowing them to perform photosynthesis where light intensities are very low. This enables them to thrive at great depths where light penetration is poor.

Question 6

Diazotrophs maximize nitrogenase activity by

Accepted Answer

Diazotrophs typically produce specialized structures such as heterocysts or fix N₂ at times when oxygen is absent to protect nitrogenase from oxygen. This is because nitrogenase is a highly oxygen-sensitive enzyme and requires an oxygen-free environment to function properly.

Question 7

Dissimilative iron-reducing bacteria couple which oxidation-reduction reactions?

Accepted Answer

Dissimilative iron-reducing bacteria use the oxidation of H₂ or organic compounds as an electron source and reduce ferric iron or manganese as an electron acceptor. This is known as dissimilative Fe(III) reduction or Fe(III)-reducing bacteria. They do not ferment sugars or perform photosynthesis.

Question 8

What growth conditions would you use to enrich for ammonia-oxidizing bacteria?

Accepted Answer

Ammonia-oxidizing bacteria are aerobic, so they require oxygen to grow. They also use ammonia as their energy source, so a mineral media with ammonia would be suitable for enrichment. The presence of bicarbonate would provide a source of carbon for the bacteria. Incubation in the dark would minimize the growth of other organisms that might compete with the ammonia-oxidizing bacteria.

Question 9

Epibiotic predators

Accepted Answer

Epibiotic predators obtain nutrients by attaching to the surface of their prey. They do not invade the cytoplasm or periplasmic space of the prey, and swarming behavior is not typically associated with epibiotic predation.

Question 10

What microbes have a symbiotic association with mussels, living in their gill tissue?

Accepted Answer

The answer of What microbes have a symbiotic association with...

Question 11

What is the difference between a methylotroph and methanotroph?

Accepted Answer

Methylotrophs use organic carbon lacking C-C bonds as electron donors and carbon sources, while methanotrophs exclusively use methane as an electron donor and carbon source. This is the main difference between the two types of organisms.

Question 12

Which of the following functional groups would you expect to find in aerobic iron- and sulfur-rich acidic mine drainage?

Accepted Answer

Dissimilative iron-oxidizers are microorganisms that can oxidize iron in aerobic conditions, which are typical in acidic mine drainage environments rich in iron and sulfur.

Question 13

Thioploca species contain large vacuoles that store ________, which is used to ________ under anaerobic conditions.

Accepted Answer

Thioploca species contain large vacuoles that store nitrate, which is used to oxidize sulfide under anaerobic conditions.

Question 14

In symbiotic associations between sulfur chemolithotrophs and eukaryotes such as tube worms and giant clams, the bacterial symbiont provides ________ while the host provides ________.

Accepted Answer

The answer of In symbiotic associations between sulfur chemolithotrophs and...

Question 15

The Bacteria and Archaea are the ONLY domains in which organisms exist that can

Accepted Answer

Bacteria and Archaea are the only domains that include organisms capable of conserving energy from the transformation of inorganic nitrogen species, such as through processes like nitrification and denitrification.

Question 16

What is one especially unique characteristic of methanotrophs?

Accepted Answer

Methanotrophs are unique because they have unusually large amounts of sterols, which is not a common feature among bacteria. This characteristic helps them in stabilizing their cell membranes when they oxidize methane.

Question 17

Dissimilatory sulfide-oxidizers use a variety of unique ecological strategies in order to

Accepted Answer

Dissimilatory sulfide-oxidizers must position themselves at interfaces where sulfide and oxygen meet, as they use oxygen to oxidize sulfide for energy. This is essential for their survival and ecological niche.

Question 18

In which of the following environments would you expect to find a high number of iron-reducing bacteria?

Accepted Answer

Iron-reducing bacteria are commonly found in anaerobic environments such as the deep subsurface, where they can use iron as an electron acceptor in the absence of oxygen.

Question 19

Escherichia coli is a chemoorganotrophic, facultative aerobe and belongs to the phylum Proteobacteria. Based on this information, which of the following functional groups does E. coli most likely belong to?

Accepted Answer

E. coli is a facultative aerobe, meaning it can switch between aerobic respiration and anaerobic processes such as fermentation or anaerobic respiration. Among the options, denitrifying bacteria are capable of anaerobic respiration, converting nitrates into nitrogen gas under oxygen-limited conditions, which aligns with the facultative aerobic nature of E. coli.

Question 20

Which of the following traits do ammonia and nitrite oxidizers share?

Accepted Answer

Ammonia and nitrite oxidizers are both autotrophic, meaning they fix carbon dioxide to form organic compounds, and aerobic, as they require oxygen to oxidize ammonia and nitrite, respectively.

Quiz 15: Functional Diversity of Microorganisms

Most methanotrophs are obligate because .