Question 1

Even to a well-trained microbiologist, isolates of Streptomyces when grown on a nutrient agar plate can appear as though they are fungi. Describe key similarities of how these two unrelated groups can so easily be mistaken for each other, and then propose methods to conclusively distinguish between them.

Accepted Answer

The answer of Even to a well-trained microbiologist, isolates of...

Question 2

Except that they are not produced in the cytoplasm, conidia produced by Streptomyces spp. are chemically quite similar in composition to endospores produced by Bacillus spp.

Accepted Answer

While both conidia and endospores are resistant, dormant forms of bacterial cells, they differ in their mode of production and chemical composition. Conidia are produced through a process called sporulation, which occurs in specialized structures called spore-bearing hyphae. They are typically composed of a single cell and lack some of the protective structures found in endospores, such as a thick coat of keratin-like proteins. In contrast, endospores are produced by a process called sporogenesis, which occurs within the cytoplasm of the bacterial cell. They are highly resistant to environmental stressors and contain a variety of protective structures, including a spore coat, cortex, and inner membrane.

Question 3

Due to the slow and varied growth rates, mycobacteria are commonly grouped into either slow growing or very slow growing, which has consequences on the growth medium selected for culturing.

Accepted Answer

The answer of Due to the slow and varied growth...

Question 4

Select a group within Bacteria that has rare cell morphology observable with a microscope. Describe the appearance, the group that it corresponds to, and another group that would certainly be ruled out when observing this type of cell morphology.

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Question 5

Explain how the enteric bacteria can be differentiated by the type and proportion of fermentation products produced by the anaerobic fermentation of glucose.

Accepted Answer

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Question 6

During stationary phase, group members of Serratia produce prodigiosins that contain pyrrole. Considering its structural relatedness to other pyrrole-containing molecules of known function (e.g., chlorophylls, bacteriochlorophylls, porphyrins), propose a potential ecological role for these compounds in soil where they are involved in something other than photosynthesis.

Accepted Answer

The answer of During stationary phase, group members of Serratia...

Question 7

When looking under a transmission electron microscope, you observe pirellulosome in a bacterium. This bacterium likely belongs to the Planctomycetes.

Accepted Answer

Pirellulosomes are a defining feature of planctomycetes bacteria, so if you observe them under a transmission electron microscope, it is a good indication that the bacterium belongs to this phylum.

Question 8

Considering the evolution of Bacteria, the criteria used for taxonomy, and the genetic requirements for individual metabolic pathways, explain how it is unlikely to observe three genera of the same family where one genus has strict anaerobes that degrade only small aromatics, another genus degrades large molecular weight sugars aerobically, and a third is a photoautotroph.

Accepted Answer

The answer of Considering the evolution of Bacteria, the criteria...

Question 9

Deinococcus radiodurans is capable of withstanding especially high levels of radiation, and the carotenoids they produce enhance this resistance.

Accepted Answer

Deinococcus radiodurans is known for its ability to survive extreme radiation, and the carotenoids it produces are believed to contribute to this resilience. The carotenoids function as antioxidants, neutralizing harmful free radicals produced by radiation and protecting the organism's cellular components from damage.

Question 10

Antibiotics that disrupt or halt cell wall biosynthesis are actually ineffective at harming growth of mycoplasmas.

Accepted Answer

Mycoplasmas lack a cell wall, so antibiotics that target cell wall synthesis, such as penicillin, are ineffective against them.

Question 11

Thermotoga species are hyperthermophiles and appear relatively closely related to Archaea in comparison to other bacteria such as Salmonella.

Accepted Answer

Thermotoga species are indeed hyperthermophiles and are classified as members of the bacterial phylum Thermotogae. However, their phylogenetic relationship to Archaea is still a matter of debate and some studies suggest they may be more distantly related to Archaea than previously thought.

Question 12

Some species in the genus Acidobacteria are classified in Bacteria while others are considered Archaea.

Accepted Answer

All species in the genus Acidobacteria are classified within the domain Bacteria; none are classified as Archaea.

Question 13

The hypothesis that H₂ was a key electron donor for energy metabolism in primitive organisms is supported by it being such a common trophic strategy in Aquificae.

Accepted Answer

The statement is true. The Aquificae bacteria have evolved to use H₂ as a key electron donor for their energy metabolism and thus support the hypothesis.

Question 14

Compare and contrast the human pathogens and non-pathogens in Clostridium. Propose a reason for why this differentiation is challenging to assay in the laboratory (NOT on living eukaryotic animal models).

Accepted Answer

The answer of Compare and contrast the human pathogens and...

Question 15

Chlamydiae are most commonly transmitted throughout environments by insects.

Accepted Answer

Chlamydiae are primarily sexually transmitted, but can also be spread through contact with infected bodily fluids, such as during childbirth or through sharing contaminated objects. There is no evidence to suggest that insects are a significant mode of transmission for chlamydiae.

Question 16

Which group of bacteria is most famous for their diversity of antibiotics produced? What could be an ecological role of antibiotic production by bacteria when the antibiotics are not produced at a sufficiently high level to be lethal?

Accepted Answer

The answer of Which group of bacteria is most famous...

Question 17

Cytophaga columnaris causes columnaris (or ʺcottonmouthʺ) disease in fish such as salmon. Based on its taxonomic group, predict some of the activities this bacterium has during infection of fish. Also mention one related taxon that likely has some of the same functions and another taxon that does not.

Accepted Answer

The answer of Cytophaga columnaris causes columnaris (or ʺcottonmouthʺ) disease...

Question 18

Simple staining and microscopy could easily distinguish the different taxa intermixed within a community of Sarcina, Staphylococcus, and coryneform bacteria.

Accepted Answer

Simple staining and microscopy techniques can easily distinguish different bacteria based on their morphology, size, and arrangement. Sarcina, Staphylococcus, and coryneform bacteria have distinct morphologies and can be differentiated from each other through simple staining and microscopy.

Question 19

Some Streptomyces spp. can biosynthesize several chemically unrelated structures that act as different antibiotics.

Accepted Answer

Streptomyces spp., commonly found in soil, are known to produce multiple antibiotics such as streptomycin, tetracycline, and chloramphenicol.

Question 20

Proteobacteria members thrive in soils and occur at high concentrations as well. Other bacterial taxa are considered much less diverse in terms of their metabolic capabilities. Due to the role isolation has in discovering metabolic pathways, consider how obtaining hundreds of new isolates from a less studied phylum might change our views on metabolic diversity. Predict how the results of discovering another highly metabolically diverse group might be handled in terms of taxonomic assignment.

Accepted Answer

The answer of Proteobacteria members thrive in soils and occur...

Quiz 16: Diversity of Bacteria