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NMCN Professional Exam Bacteriology — practice questions

Explore 38 free Bacteriology questions in NMCN Professional Exam Microbiology. Open each question or exercise to read its content, reference answers and available explanation.

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Bacteriology questions and exercises with answers

Showing questions 1–30 of 38.

Which material forms the cell wall of a bacterium?Read the answer and worked solution →In a Gram-positive bacterium, peptidoglycan accounts for what share of the cell wall?Read the answer and worked solution →What lies immediately outside the thin peptidoglycan wall of a Gram-negative bacterium?Read the answer and worked solution →How does an archaean cell wall differ from a bacterial one?Read the answer and worked solution →Water floods into a bacterium sitting in dilute fluid. What does its cell wall prevent?Read the answer and worked solution →Which statement pairs a basic prokaryotic shape with the right description?Read the answer and worked solution →Where does a prokaryote keep its single circular chromosome?Read the answer and worked solution →Which prokaryotic appendage is used for locomotion?Read the answer and worked solution →Many antibiotics hit bacterial wall construction because their structure mimics which molecules?Read the answer and worked solution →What distinguishes the lipids of an archaeal plasma membrane from a bacterial one?Read the answer and worked solution →Which agent carries chromosomal DNA from one bacterium to another during transduction?Read the answer and worked solution →Conjugation moves DNA between prokaryotes using which structure?Read the answer and worked solution →Bacteriophages shuttle genes between bacteria. What is the equivalent situation in archaea?Read the answer and worked solution →Imprudent and excessive antibiotic use increases resistant bacteria by which mechanism?Read the answer and worked solution →MRSA takes its name from resistance to which set of drugs?Read the answer and worked solution →How does community-associated MRSA differ from MRSA seen inside healthcare facilities?Read the answer and worked solution →Why does feeding livestock routine low doses of antibiotics worry clinicians?Read the answer and worked solution →Why is prescribing an antibiotic for a cold or the flu treated as misuse?Read the answer and worked solution →What holds the cells of a biofilm together?Read the answer and worked solution →What share of infections acquired in hospital is attributed to biofilms?Read the answer and worked solution →How much antibiotic can bacteria in a biofilm withstand compared with free-living cells?Read the answer and worked solution →The Black Death is believed to have been an outbreak of which disease?Read the answer and worked solution →DNA recovered from an Athenian mass grave pointed to which agent for the Plague of Athens?Read the answer and worked solution →Which organism produces the toxin responsible for botulism?Read the answer and worked solution →A patient develops bloody diarrhea days after eating raw spinach. Which agent fits best?Read the answer and worked solution →A disease that is constantly present at low incidence in a population is described as what?Read the answer and worked solution →High doses of antibiotics can let which organism overgrow the gut and cause chronic diarrhea?Read the answer and worked solution →Roughly what proportion of recently emerging human infectious diseases are zoonoses?Read the answer and worked solution →Which organisms carry out biological nitrogen fixation?Read the answer and worked solution →Why must a legume root nodule stay free of oxygen?Read the answer and worked solution →

Worked practice questions

Which material forms the cell wall of a bacterium?

  1. Peptidoglycan, a cross-linked polymer
  2. Cellulose, a plant-type wall polymer
  3. Chitin, the wall polymer of fungi
  4. Cholesterol, a membrane sterol lipid
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Correct answer: A. Peptidoglycan, a cross-linked polymer

1. The bacterial wall is built from peptidoglycan, polysaccharide chains cross-linked by unusual peptides. 2. Those peptides carry both L- and D-amino acids, which is what makes the wall a drug target. 3. Cellulose walls belong to plants, and chitin walls belong to fungi and insects, not to bacteria. 4. Cholesterol is a lipid, so it could never give the wall its rigid cross-linked mesh. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 22 "Prokaryotes: Bacteria and Archaea", section 22.2 Structure of Prokaryotes_

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In a Gram-positive bacterium, peptidoglycan accounts for what share of the cell wall?

  1. About 10 percent of the total wall
  2. Up to 90 percent of the total wall
  3. About 50 percent of the total wall
  4. Under 5 percent of the total wall
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Correct answer: B. Up to 90 percent of the total wall

1. Gram-positive organisms build a thick wall, and up to 90 percent of it is peptidoglycan. 2. Most of the remainder is made of acidic substances called teichoic acids. 3. The 10 percent figure belongs to Gram-negative bacteria, whose wall is only a few peptidoglycan layers thick. 4. That thickness difference is why the two groups respond differently to Gram staining. 5. Values of 50 percent and 5 percent match neither group. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 22 "Prokaryotes: Bacteria and Archaea", section 22.2 Structure of Prokaryotes_

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What lies immediately outside the thin peptidoglycan wall of a Gram-negative bacterium?

  1. A thick sheath of teichoic acids
  2. A capsule made of pure protein
  3. An envelope of lipopolysaccharides
  4. A second wall of pseudopeptidoglycan
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Correct answer: C. An envelope of lipopolysaccharides

1. A Gram-negative wall is only a few layers of peptidoglycan, about 10 percent of the total wall. 2. Surrounding it is an outer envelope containing lipopolysaccharides and lipoproteins. 3. That envelope is sometimes called a second lipid bilayer, although its chemistry differs from a plasma membrane. 4. Teichoic acids are a Gram-positive feature, so they cannot be the outer layer here. 5. Pseudopeptidoglycan is one of the four archaean wall types, not a bacterial layer. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 22 "Prokaryotes: Bacteria and Archaea", section 22.2 Structure of Prokaryotes_

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