BIOTECHNOLOGY_ FOODBORNE ILLNESS

Which of the following best distinguishes Gram‐positive from Gram‐negative bacteria regarding their cell wall structure?

• A. Thicker peptidoglycan layer with teichoic acids in Gram‐positive bacteria.

• B. Thin peptidoglycan layer and the presence of lipopolysaccharides in the cell wall.

• C. Presence of an outer capsule composed of polysaccharides.

• D. Possession of cytoplasmic membranes only.

Which characteristic of bacterial cell physiology contributes most significantly to antibiotic resistance in many pathogens?

• A. Expression of efflux pumps.

• B. Formation of biofilms.

• C. Alterations in cell wall permeability.

• D. Spore formation in bacteria.

Which statement about bacterial DNA structure is most accurate?

• A. It consists of a linear chromosome with telomeric ends.

• B. It includes a circular chromosome often accompanied by plasmids.

• C. It is segmented into multiple distinct chromosomal pieces like eukaryotes.

• D. It contains introns and extensive non-coding regions.

Which mechanism is primarily responsible for the systemic symptoms seen in many bacterial infections?

• A. Direct cellular invasion leading to tissue necrosis.

• B. Localized toxin production without immune system involvement.

• C. Endotoxin release alone causing cellular damage.

• D. A robust immune-mediated inflammatory response.

Bacterial spoilage of food is mainly due to which of the following processes?

• A. Enzymatic autolysis of food tissue under sterile conditions.

• B. Acid fermentation that preserves food.

• C. Proteolytic degradation of food proteins by bacterial enzymes.

• D. Lipid oxidation driven by environmental factors.

What is the primary mechanism by which bacteria adhere to food surfaces?

• A. Passive diffusion resulting in uniform distribution.

• B. Active transport using membrane proteins to enter cells.

• C. Biofilm formation through pili and adhesins.

• D. Osmosis leading to concentration gradients on surfaces.

Considering the complexity of biofilms, which component is essential for maintaining their integrity on food surfaces?

• A. Extracellular polymeric substances (EPS).

• B. Cytoplasmic enzymes secreted during growth.

• C. Ribosomal RNA released from lysed cells.

In tracing bacterial contamination in food, which of the following is the most comprehensive initial step?

• A. Direct molecular typing using advanced techniques only.

• B. Sampling and enrichment culture to increase bacterial numbers.

• C. Direct microscopic examination without sample preparation.

• D. Performing an antibiogram before isolating the bacteria.

Which advanced microbiological testing process integrates both phenotypic and genotypic methods for identifying bacteria in food contamination cases?

• A. Polymerase chain reaction (PCR) combined with biochemical assays.

• B. Gram staining followed solely by light microscopy.

• C. Solely serological testing based on antigen-antibody reactions.

• D. Culture on selective media without further identification steps.

When designing a protocol to detect unknown bacteria in a food sample, which sequence of steps is most methodologically robust?

• A. Direct PCR amplification followed by immediate serotyping.

• B. Sample collection, enrichment culture, selective isolation, phenotypic characterization, then genetic sequencing.

• C. Electron microscopy for initial identification followed by Gram staining.

• D. Immediate biochemical assays without prior enrichment to save time.