Question 1

Many Listeria spp. grow well at cold temperatures, so although refrigeration is excellent at preventing growth of most other pathogens, it is NOT very useful at minimizing growth of contaminated foods.

Accepted Answer

This is correct. Listeria is known to grow well at cold temperatures, including in refrigerated food. This means that refrigeration is not very effective at preventing the growth of Listeria compared to other pathogens that do not thrive at cooler temperatures. Other food safety measures, such as proper cooking and pasteurization, are needed to effectively control Listeria in food products.

Question 2

Which bacterial genus is LEAST related to the others listed?

Accepted Answer

While all of the listed bacterial genera belong to the phylum Actinobacteria, Mycobacterium is distinct in several ways, including its unique cell wall structure and the fact that it is an obligate aerobe. The other genera listed are more closely related to each other and share many similarities in their morphology, physiology, and ecological roles.

Question 3

Which of the following is NOT a trait of the Planctomycetes?

Accepted Answer

The Planctomycetes are a group of bacteria known for their budding cell division and unique intracellular compartmentalization, as well as their unusual lack of peptidoglycan in their cell walls. However, they are not known for their ability to undergo plant symbiosis, so choice D is the correct answer.

Question 4

Despite ether-linked lipids being a hallmark of the Archaea, the thermophilic sulfate-reducing bacteria in ________ also contain ether-linked lipids, which suggests they may be more closely related to Archaea than many other groups in Bacteria.

Accepted Answer

The statement in the question suggests that thermophilic sulfate-reducing bacteria in Thermodesulfobacterium contain ether-linked lipids, which is a characteristic of Archaea. This suggests that Thermodesulfobacterium may be more closely related to Archaea than other groups within Bacteria. The other options (Aquifex, Thermus, and Verrucomicrobium) do not have the same evidence linking them to ether-linked lipids and Archaea.

Question 5

To subgroup the lactic acid bacteria, which are incapable of aerobic degradation and only do fermentation, identifying products formed is a useful way to distinguish homofermentative versus heterofermentative lactic acid bacteria.

Accepted Answer

Identifying products formed can indeed help distinguish homofermentative and heterofermentative lactic acid bacteria, as the former only produce lactic acid as a product of fermentation while the latter produce both lactic acid and other compounds like ethanol and acetic acid.

Question 6

Sulfur metabolism is a common trait in Deltaproteobacteria.

Accepted Answer

Sulfur metabolism is a common trait in Deltaproteobacteria, as many members of this bacterial class are involved in sulfur cycling in various environments such as sediments, deep sea, and hydrothermal vents. Examples include Desulfovibrio, Desulfobacter, and Desulfotalea.

Question 7

The enteric bacteria are a group classified within Proteobacteria that cause disease in animals.

Accepted Answer

The enteric bacteria are a group within Proteobacteria that include many important pathogenic species that cause disease in animals, including Escherichia coli, Salmonella, and Vibrio cholerae.

Question 8

Which structural feature is common in BOTH Planctomycetes and Verrucomicrobia but RARELY found in bacteria outside these two phyla?

Accepted Answer

Both Planctomycetes and Verrucomicrobia are known for their unique intracellular compartmentalization, which is rare in bacteria outside of these two phyla. Prosthecae appendages are common in other bacterial phyla such as Alphaproteobacteria and Betaproteobacteria. Sheath-like toga cell envelopes are found in the phylum Chloroflexi. Tubulins are not unique to these two phyla and are found in many eukaryotes as well.

Question 9

Many gammaproteobacteria members are obligate intracellular symbionts of eukaryotes, which also enables many to become human pathogens.

Accepted Answer

The answer of Many gammaproteobacteria members are obligate intracellular symbionts...

Question 10

Betaproteobacteria is a functionally diverse group that primarily uses anaerobic metabolisms.

Accepted Answer

Betaproteobacteria is a functionally diverse group that has both aerobic and anaerobic metabolisms. They also have a wide range of ecologies, including pathogenic, symbiotic, and free-living lifestyles.

Question 11

Bacteria in the phylum ________ occur as elementary or reticulate bodies depending on their life cycle stage, are obligate intracellular parasites, and also have relatively small genomes.

Accepted Answer

Chlamydiae bacteria have a unique life cycle in which they alternate between two distinct forms: elementary bodies, which are the infectious stage, and reticulate bodies, which are the replicating stage. They are obligate intracellular parasites, meaning they cannot replicate outside of a host cell. Chlamydiae also have relatively small genomes compared to other bacteria, with many of their metabolic pathways being lost or highly reduced due to their intracellular lifestyle.

Question 12

Members of the ________ are the most abundant bacteria present in the large intestine of humans and contain unusual ________ in their cell membranes.

Accepted Answer

Members of the Bacteroides genus are the most abundant bacteria in the human large intestine and are notable for containing unusual sphingolipids in their cell membranes, distinguishing them from many other bacteria that primarily contain glycerolipids.

Question 13

The ________ produce over 500 characterized antibiotics.

Accepted Answer

Streptomycetes are known for their ability to produce numerous antibiotics, with over 500 characterized so far. Bacteroidetes, mycobacteria, and pseudomonads also have the ability to produce antibiotics, but not to the same extent as streptomycetes. Therefore, D) streptomycetes is the best choice.

Question 14

Rhodobacter and Roseobacter are two genera with a common ancestor in Alphaproteobacteria.

Accepted Answer

Rhodobacter and Roseobacter are both genera in the order Rhodobacterales within the class Alphaproteobacteria. They share a common ancestor within this class.

Question 15

A soil sample was diluted into a nutrient broth, then spread onto a plate and grown for one week at room temperature. Several colonies appeared dusty or fuzzy and yet were identified as bacteria-not as fungi. Which genus do these isolates likely belong in?

Accepted Answer

Streptomyces are known for their fuzzy, filamentous growth pattern, and are often mistaken for fungi. However, they are actually bacteria and are commonly found in soil. Actinomyces, Mycobacterium, and Nocardia are also common soil-dwelling bacteria, but they do not typically exhibit a fuzzy or filamentous growth pattern.

Question 16

The most metabolically diverse phylum of Bacteria known to date is the Proteobacteria.

Accepted Answer

Proteobacteria are the most metabolically diverse phylum of Bacteria known to date, comprising a wide range of pathogenic, symbiotic, and free-living organisms.

Question 17

Members of the ________ are particularly abundant in the oceans, chemoorganotrophic, rarely pathogenic, and often produce pigments when grown on complex media.

Accepted Answer

Flavobacteriales are known for their abundance in marine environments, their chemoorganotrophic metabolism, rarity as pathogens, and their tendency to produce pigments when cultured on complex media.

Question 18

Pseudomonads are aerobic, gram-positive, polar flagellated, bacillus-shaped cells.

Accepted Answer

Pseudomonads are actually aerobic, gram-negative, polar flagellated, bacillus-shaped cells.

Question 19

Agrobacterium tumefaciens can form root nodules in plants and can mate with bacteria, which makes it an excellent host organism for genetic transformations among different domains of life.

Accepted Answer

Agrobacterium tumefaciens is known for causing crown gall disease in plants by transferring part of its DNA to the plant cells, leading to tumor formation, not root nodules. Root nodules are typically formed by nitrogen-fixing bacteria such as Rhizobium species in legumes. While Agrobacterium tumefaciens is widely used for genetic transformations in plants, the statement about forming root nodules and mating with bacteria to facilitate transformations across different domains of life is inaccurate.

Question 20

Due to the genetic similarities of non-pathogenic and pathogenic enterics, phenotypic assays are often performed in favor over taxonomy-based sequencing/probing to distinguish pathogens from non-pathogens.

Accepted Answer

Phenotypic assays, such as biochemical tests, are commonly used to distinguish between pathogenic and non-pathogenic enterics because of genetic similarities between the two groups. This is often preferred over taxonomic sequencing/probing, which can be time-consuming and costly.

Quiz 16: Diversity of Bacteria