Surface adhesion structures: Which organisms may possess fimbriae (short, hair-like attachment structures)?

Introduction / Context:
Fimbriae (also called attachment pili) are short, filamentous surface structures that promote adhesion to host tissues, abiotic surfaces, and other cells. They are important in colonization, biofilm formation, and virulence.

Given Data / Assumptions:

• Classic microbiology texts emphasize fimbriae as especially common in Gram-negative bacteria.
• Terminology varies: some Gram-positive species produce sortase-assembled pili, often discussed separately from classical Gram-negative fimbriae.
• The question likely expects the traditional association.

Concept / Approach:

In Gram-negative bacteria, fimbriae are assembled by dedicated secretion and assembly pathways and often recognize specific receptors on host cells (e.g., uropathogenic E. coli P fimbriae). While Gram-positive bacteria can have pili, the textbook convention associates “fimbriae” primarily with Gram-negative species, reflecting historical discovery and structural differences.

Step-by-Step Solution:

Verification / Alternative check:

Model organisms such as E. coli, Neisseria, and Salmonella illustrate fimbrial adhesins and their roles in disease. Laboratory assays show hemagglutination, mannose-sensitive binding, and biofilm formation driven by these structures.

Why Other Options Are Wrong:

Gram-positive only: understates the classical association.

Both: would be acceptable in nuanced discussions of pili but diverges from the conventional “fimbriae = Gram-negative” emphasis likely intended here.

None: incorrect; fimbriae are well documented.

Common Pitfalls:

Equating all surface fibers across bacteria; structural and assembly differences matter. Also, confusing long conjugative pili (involved in DNA transfer) with short fimbriae (adhesion).

Final Answer:

Gram-negative bacteria