Fundamentals of Bacteriology

What is the main structural component of the bacterial cell wall?

Peptidoglycan made of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) crosslinked by transpeptidase.

Which acid is found only in Gram-positive cell walls and is a target for TLR2?

Lipoteichoic acid.

Which acid is found only in acid-fast bacteria such as Mycobacteria?

Mycolic acid.

Which bacterial group has a thick peptidoglycan layer?

Gram-positive bacteria.

What structural feature provides toxicity in LPS of Gram-negative bacteria?

Lipid A (triggers septic shock via TLR4/CD14).

Which domain of LPS is the target for host antibodies?

O-antigen.

Which bacteria contain lipooligosaccharide (LOS) instead of full LPS?

Neisseria and Haemophilus species.

What enzyme is located in the periplasmic space of Gram-negative bacteria that contributes to antibiotic resistance?

β-lactamase.

What is the function of the inner (cytoplasmic) membrane?

Acts as a phospholipid bilayer controlling transport and energy generation.

Which bacterial appendage mediates motility?

Flagellum.

Which bacterial structure mediates adherence to host cells and DNA exchange?

Pilus (fimbriae).

What is the purpose of a bacterial capsule?

Protects against phagocytosis and desiccation.

Which specialized extracellular structure allows survival in harsh environments?

Endospore (contains dipicolinic acid).

What is a biofilm and why is it clinically important?

Community of bacteria in a polysaccharide matrix that protects from antibiotics and immune responses.