Question 1

Which of the following statements best describes the Gram-negative cell envelope found in Proteobacteria?

Accepted Answer

It has a thin peptidoglycan layer, an outer membrane with lipopolysaccharide (LPS), and is less sensitive to penicillin.

Question 2

Which metabolic trait is shared by all members of the phylum Proteobacteria?

Accepted Answer

Gram-negative cell envelope structure

Question 3

A patient presents with a severe wound infection after a hospital stay. The causative agent is catalase and oxidase positive, uses O$$_2 or NO$_3^-$$ for respiration, and is resistant to many antibiotics. Which genus is most likely responsible?

Accepted Answer

Pseudomonas

Question 4

Which of the following best explains why Cyanobacteria are critical to both the global carbon and nitrogen cycles?

Accepted Answer

They fix CO$$_2$$ via the Calvin Cycle and can convert N$$_2 to NH$_3$$ through nitrogen fixation.

Question 5

Which unique structure is found in Spirochetes and is responsible for their corkscrew motility?

Accepted Answer

Axial filaments (endoflagella) located in the periplasmic space

Question 6

Which of the following bacteria is an obligate intracellular parasite, lacks peptidoglycan, and can cause both sexually transmitted infections and blindness?

Accepted Answer

Chlamydia trachomatis

Question 7

Which phylum is characterized by high G+C content in DNA, filamentous growth, and the production of many antibiotics?

Accepted Answer

Actinobacteria

Question 8

A bacterium is isolated from hot springs and is found to possess a heat-stable DNA polymerase used in PCR. To which phylum does it most likely belong?

Accepted Answer

Deinococcus-Thermus

Question 9

Which of the following best describes the life cycle of Myxobacteria?

Accepted Answer

Aggregation of cells into a fruiting body, formation of myxospores, and germination under favorable conditions

Question 10

Which genus is a facultative anaerobe, catalase positive, non-motile, and includes both major pathogens and common skin commensals?

Accepted Answer

Staphylococcus

Question 11

Which of the following is a distinguishing feature of Mycoplasmas (phylum Tenericutes)?

Accepted Answer

Absence of a cell wall and highly variable shapes

Question 12

Which of the following bacteria is commonly found in the human colon, is anaerobic, and belongs to the phylum Bacteroidetes?

Accepted Answer

Bacteroides

Question 13

Which of the following best describes the medical importance of acid-fast bacteria such as Mycobacterium?

Accepted Answer

They cause diseases such as tuberculosis and leprosy due to their waxy, mycolic acid-rich cell envelope.

Question 14

Which of the following is true about the genus Bacillus?

Accepted Answer

They are aerobic, form resistant endospores, and some produce antibiotics or insecticidal toxins.

Question 15

Which of the following best describes the difference between Pseudomonas and Enterobacteria such as E. coli?

Accepted Answer

Pseudomonas are oxidase positive and do not ferment, while Enterobacteria are oxidase negative and can ferment.

Question 16

Which of the following is a unique feature of Planctomycetes?

Accepted Answer

Presence of a nucleoid surrounded by an infolded plasma membrane resembling a nuclear envelope

Question 17

Which of the following bacteria is a facultative anaerobe, catalase negative, non-motile, and ferments carbohydrates to lactic acid?

Accepted Answer

Streptococcus

Question 18

Which of the following best describes the environmental importance of methanotrophs?

Accepted Answer

They oxidize methane to CO$$_2$$, reducing greenhouse gas emissions.

Question 19

Which of the following is a common feature of all Firmicutes?

Accepted Answer

Gram-positive cell wall structure with low G+C DNA content

Question 20

Which of the following best describes the function of heterocyst cells in Cyanobacteria?

Accepted Answer

Nitrogen fixation in an anaerobic environment

Phylogenetic Diversity of Bacteria: Major Phyla, Cell Structure, and Ecological Roles Chapter 16

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