Search results
Results From The WOW.Com Content Network
As the primary antigenic determinants, virulence factors and impunity factors on the cell surface of a number of species of gram-negative and some gram-positive bacteria, including Enterobacteriaceae, Pseudomonadaceae, and Neisseriaceae, there has been much interest in the study of pili as an organelle of adhesion and as a vaccine component.
Although not all bacteria have pili or fimbriae, bacterial pathogens often use their fimbriae to attach to host cells. In Gram-negative bacteria, where pili are more common, individual pilin molecules are linked by noncovalent protein-protein interactions, while Gram-positive bacteria often have polymerized LPXTG pilin. [1]
Chaperone-usher fimbriae (CU) are linear, unbranching, outer-membrane pili secreted by gram-negative bacteria through the chaperone-usher system rather than through type IV secretion or extracellular nucleation systems.
The highly charged nature of lipopolysaccharides confer an overall negative charge to the Gram -negative cell wall. The chemical structure of the outer membrane lipopolysaccharides is often unique to specific bacterial strains, and is responsible for many of their antigenic properties.
The pathogenic species along with some commensal species, have type IV pili which serve multiple functions for this organism. Some functions of the type IV pili include: mediating attachment to various cells and tissues, twitching motility, natural competence, microcolony formation, extensive intrastrain phase, and antigenic variation.
Twitching motility is a form of crawling bacterial motility used to move over surfaces. Twitching is mediated by the activity of hair-like filaments called type IV pili which extend from the cell's exterior, bind to surrounding solid substrates, and retract, pulling the cell forwards in a manner similar to the action of a grappling hook.
A Gram stain of a urethral exudate showing typical intracellular Gram-negative diplococci, which is diagnostic for gonococcal urethritis [17]. Neisseria species are fastidious, Gram-negative cocci (though some species are rod-shaped and occur in pairs or short chains) that require nutrient supplementation to grow in laboratory cultures. [18]
The Type IV secretion system (T4SS) is the general mechanism by which bacterial cells secrete or take up macromolecules. Their precise mechanism remains unknown. T4SS is encoded on Gram-negative conjugative elements in bacteria. T4SS are cell envelope-spanning complexes, or, in other words, 11–13 core proteins that form a channel through ...