Many bacteria that cause diseases must be able to survive inside and outside the host. Attachment to and colonization of abiotic or biotic surfaces is a common mechanism by which various microorganisms enhance their ability to survive in diverse environments. Vibrio cholerae is a Gram-negative aquatic bacillus that is often found in the environment attached to the chitinous exoskeletons of zooplankton. It has been suggested that attachment to zooplankton enhances environmental survival of Vibrio spp., probably by providing both an abundant source of carbon and nitrogen and protection from numerous environmental challenges. On ingestion by humans, some serogroups of V. cholerae cause the diarrhoeal disease cholera. The pathophysiology of cholera is a result of the effects of cholera toxin on intestinal epithelial cells. For sufficient quantities of cholera toxin to reach the intestinal epithelium and to produce clinical symptoms, colonization of the small bowel must occur. Because most V. cholerae do not colonize humans, but all probably require strategies for survival in the environment, we considered that colonization factors selected for in the environment may be the same as those required for intestinal colonization of humans. In support of this hypothesis, here we have identified a single protein required for efficient intestinal colonization that mediates attachment to both zooplankton and human epithelial cells by binding to a sugar present on both surfaces.

A colonization factor links Vibrio cholerae environmental survival and human infection

The interaction of Vibrio cholerae with chitin exemplifies for microbial ecology a successful bacteria-substrate interaction with complex and significant influence on the lifestyle of the bacterium. Chitin is one of the most abundant polymers on earth and possibly the most abundant in the aquatic environment, where its association with V. cholerae has provided the microorganism with a number of advantages, including food availability, adaptation to environmental nutrient gradients, tolerance to stress and protection from predators. Emergent properties of V. cholerae-chitin interactions occur at multiple hierarchical levels in the environment and include cell metabolic and physiological responses e.g. chemotaxis, cell multiplication, induction of competence, biofilm formation, commensal and symbiotic relationship with higher organisms, cycling of nutrients, and pathogenicity for humans and aquatic animals. As factors mediating virulence of V. cholerae for humans and aquatic animals derive from mechanisms of adaptation to its environment, at different levels of hierarchical scale, V. cholerae interactions with chitin represent a useful model for examination of the role of primary habitat selection in the development of traits that have been identified as virulence factors in human disease.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1462-2920.2007.01559.x

Global impact of Vibrio cholerae interactions with chitin.

Lipopolysaccharides of Vibrio cholerae. I. Physical and chemical characterization

Vibrio cholerae is a bacterial pathogen that colonizes the chitinous exoskeleton of zooplankton as well as the human gastrointestinal tract. Colonization of these different niches involves an N-acetylglucosamine binding protein (GbpA) that has been reported to mediate bacterial attachment to both marine chitin and mammalian intestinal mucin through an unknown molecular mechanism. We report structural studies that reveal that GbpA possesses an unusual, elongated, four-domain structure, with domains 1 and 4 showing structural homology to chitin binding domains. A glycan screen revealed that GbpA binds to GlcNAc oligosaccharides. Structure-guided GbpA truncation mutants show that domains 1 and 4 of GbpA interact with chitin in vitro, whereas in vivo complementation studies reveal that domain 1 is also crucial for mucin binding and intestinal colonization. Bacterial binding studies show that domains 2 and 3 bind to the V. cholerae surface. Finally, mouse virulence assays show that only the first three domains of GbpA are required for colonization. These results explain how GbpA provides structural/functional modular interactions between V. cholerae, intestinal epithelium and chitinous exoskeletons.

http://davapc1.bioch.dundee.ac.uk/pdf/gbpa.pdf

The Vibrio cholerae colonization factor GbpA possesses a modular structure that governs binding to different host surfaces

The free-living bacteria of the genus Azospirillum live in close association with plant roots and represent one of the best-characterized plant growth promoting rhizobacteria (PGPR) The attachment of Azospirillum to the roots is essential for the establishment of an efficient association with the host plant Azospirillum cells are able to aggregate under certain environmental conditions, leading to the formation of bacterial flocs The bacterial surface plays an important role in the establishment of the bacteria-plant association as well as in the bacterial aggregation and data suggesting the involvement of extracellular polysaccharides and proteins in these phenomena have been published This review summarizes the current knowledge on the involvement of surface components in the adhesion processes of Azospirillum Emphasis is placed on A brasilense, the species that has been the subject of most studies in the Azospirillum genus

Surface Characteristics of Azospirillum brasilense in Relation to Cell Aggregation and Attachment to Plant Roots

An N-acetyl-D-glucosamine-specific cell associated hemagglutinin (HA) was isolated and purified from a strain of Vibrio cholerae 01 by chitin affinity chromatography followed by separation on Bio Gel P-150. A single stained protein band of 47 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was observed with the purified HA. HA-antisera produced a single precipitin band against the purified HA in an immunodiffusion test without exhibiting any reactivity towards purified lipopolysaccharide (LPS). Purified HA, used as solid-phase antigen in an enzyme-linked immunosorbent assay (ELISA), reacted strongly with HA-antisera but cross-reacted negligibly with antisera raised against purified LPS. Hemagglutinating activity of the purified HA was highly sensitive to N-acetyl-D-glucosamine. The immunogold-labelling method using HA-antisera confirmed the location of the HA on the surface of the bacterial cells. The HA-antisera reacted with a protein component of the homologous outer membrane preparation. A significant inhibition was observed in the adhesive capability of the V. cholerae 01 strain to isolated rabbit intestinal epithelial cells (RIEC) in vitro when the later were pre-treated with the purified HA.

N-acetyl-D-glucosamine-specific lectin purified from Vibrio cholerae 01.

The presence of three major virulence genes toxR, tcpA and ctxA as well as expression of several putative virulence factors were compared in 12 Vibrio cholerae O139 and non-O1,non-O139 strains of clinical and environmental origin All the strains possessed the gene encoding the regulatory protein TOXR None of the non-O1, non-O139 strains as well as one of the O139 environmental strains carried the genes for ctxA and tcpA Statistically significant differences in hemagglutinin and hemolysin production were observed amongst the strains depending on the source of their isolation Expression of extracellular enzymes such as protease, elastase, neuraminidase, phospholipase A and phospholipase C, however, did not vary significantly from the groups of strains isolated from different sources

Comparative analysis of cytotoxin, hemolysin, hemagglutinin and exocellular enzymes among clinical and environmental isolates of vibrio cholerae O139 and non-O1, non-O139.

Structural investigations on the lipopolysaccharide isolated from Vibrio cholera ogawa G-2102

A hemolysin was purified from a Vibrio cholerae O139 strain which moved as a single protein band of 67 kDa in SDS-PAGE. The hemolysin showed high level of phospholipase C activity. The purified phospholipase C–hemolysin demonstrated enterotoxic activity in rabbit ileal loop, suckling mice and enhanced permeability of rabbit skin. The pI of the purified hemolysin was 6.4. Erythrocytes from rabbit, chicken, guinea pig, sheep and horse were sensitive to the purified hemolysin in decreasing order of intensity. Erythrocytes from human and cow were unaffected by purified hemolysin.

D. Sasmal

Papers

N-acetyl-D-glucosamine-specific lectin purified from Vibrio cholerae 01.

Comparative analysis of cytotoxin, hemolysin, hemagglutinin and exocellular enzymes among clinical and environmental isolates of vibrio cholerae O139 and non-O1, non-O139.

Structural investigations on the lipopolysaccharide isolated from Vibrio cholera ogawa G-2102

Purification and characterisation of a hemolysin with phospholipase C activity from Vibrio cholerae O139

Studies on the partial structure of the O-antigen of Vibrio cholera, Inaba 569 B.