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Plankton use solar energy to drive the nutrient cycles that make the planet habitable for larger organisms. We can now explore the diversity and functions of plankton using genomics, revealing the gene repertoires associated with survival in the oceans. Such studies will help us to appreciate the sensitivity of ocean systems and of the ocean's response to climate change, improving the predictive power of climate models., The pursuit of knowledge of the oceans has progressed in recent years thanks to the availability of new technologies and tools. Satellites are now equipped with sensors that can measure [...]

Laboratory microcosm experiments are carried out for the quantitative comparison of the colonization of two copepod species, Acartia tonsa and Eurytemora affinis, by each of the epidemic serogroups. The difference in colonization is significant in the general predominance of Vibrio cholera O1 in cholera epidemics in rural Bangladesh where water supplies are taken directly from the environment.

Vibrio cholerae persists in aquatic environments predominantly in a nonculturable state. In this study coccoid, nonculturable V. cholerae O1 in biofilms maintained for 495 days in Mathbaria, Bangladesh, pond water became culturable upon animal passage. Culturability, biofilm formation, and the wbe, ctxA, and rstR2 genes were monitored by culture, direct fluorescent antibody (DFA), and multiplex PCR. DFA counts were not possible after formation of biofilm. Furthermore, wbe, but not ctxA, were amplifiable0 even after incubation for 54 and 68 days at room temperature ([approximately equal to]25[degrees]C) and 4[degrees]C, respectively, when no growth was detectable. Slower biofilm formation and extended culturability were observed for cultures incubated at 4[degrees]C, compared with [approximately equal to]25[degrees]C, suggesting biofilm production to be temperature dependent and linked to loss of culturability. Small colonies appearing after incubation in microcosms for 54 and 68 days at 25[degrees]C and 4[degrees]C, respectively, were wbe positive and ctxA and rstR2 negative, indicating loss of bacteriophage CTX[PHI]. The coccoid V. cholerae O1 observed as free cells in microcosms incubated for 495 days could not be cultured, but biofilms in the same microcosms yielded culturable cells. It is concluded that biofilms can act as a reservoir for V. cholerae O1 between epidemics because of its long-term viability in biofilms. In contrast to biofilms produced in Mathbaria pond water, V. cholerae O1 in biofilms present in cholera stools and incubated under identical conditions as the Mathbaria pond water biofilms could not be cultured after 2 months, indicating that those V. cholerae cells freshly discharged into the environment are significantly less robust than cells adapted to environmental conditions. Bangladesh | bacteriophage CTX[PHI] | DFA | multiplex-PCR | ctxA

A study of epidemiology and ecology of Vibrio cholerae O1 and O139 was carried out in two coastal areas, Bakerganj and Mathbaria, Bangladesh where cholera occurs seasonally. The results of bi-weekly clinical study employing culture methods, direct and enrichment culture, colony blot hybridization and direct fluorescent-antibody methods showed that cholera is endemic in both Bakerganj and Mathbaria and that V. cholerae O1, O139, and nonO1/nonO139 are autochthonous to aquatic environment.

A study was conducted to understand the effect of transporting environmental samples at the ambient air temperature on isolation and enumeration of Vibrio cholerae. The findings indicate that holding samples isolated from a freshwater ecosystem at ambient temperatures ranging from 31 degree Celsius to 35 degree Celsius for 20 hours did not have deleterious effects but rather facilitated the growth of the total heterotrophic bacteria.

The emergence of Vibrio cholerae O139 Bengal during 1992-1993 was associated with large epidemics of cholera in India and Bangladesh and, initially, with a total displacement of the existing V. cholerae 01 strains. However, the 01 strains reemerged in 1994 and initiated a series of disappearance and reemergence of either of the two serogroups that was associated with temporal genetic and phenotypic changes sustained by the strains. Since the initial emergence of the 0139 vibrios, new variants of the pathogen derived from multiple progenitors have been isolated and characterized. The clinical and epidemiological characteristics of these strains have been studied. Rapid genetic reassortment in 0139 strains appears to be a response to the changing epidemiology of V. cholerae 01 and also a strategy for persistence in competition with strains of the 01 serogroup. The emergence of V. cholerae 0139 has provided a unique opportunity to witness genetic changes in V. cholerae that may be associated with displacement of an existing serogroup by a newly emerging one and, thus, provide new insights into the epidemiology of cholera. The genetic changes and natural selection involving both environmental and host factors are likely to influence profoundly the genetics, epidemiology, and evolution of toxigenic V. cholerae, not only in the Ganges Delta region of India and Bangladesh, but also in other areas of endemic and epidemic cholera.

Research has been conducted on Vibrio vulnificus. The development of the molecular detection method for estimation of the public health risk associated with the presence of V. vulnificus is described, and the results demonstrate that special attention should be paid to the presence of pathogenic viable but nonculturable cells in environmental samples.

Research has been conducted on the Vibrio cholerae. The evaluation of the biochemical tests used for V. cholerae screening has been performed in the environmental samples and the results are reported.

Dr. Rita R. Colwell, director of the National Science Foundation, delivered this plenary address at the annual meeting of the American Institute of Biological Sciences, 24 March 2001, Arlington, Virginia. [...]

Researchers studied the presence of several virulence-associated factors in toxic and non-toxic strains of Vibrio cholerae. The virulence-associated factors included cholera toxin, hemolysin, non-O1 heat-stable enterotoxin, outer membrane protein, TCP, ToxR regulatory protein, and zonula occludens toxin.

Polymerase chain analysis of diverse serotypes and ribotypes of environmental strains of Vibrio cholerae demonstrate the presence of virulence genes or their homologues in the strains. Data suggest that this feature forms a bsis for the existence of a environmental reservoir of V. cholerae virulence genes.

Aquatic viruses can have a substantial impact on aquatic microbial populations. These viruses consist mostly of bacteriophages and algal viruses and may be even more abundant in aquatic environments than bacteria.

A genetic technique called amplified fragment length polymorphism fingerprinting shows that a single strain of Vibrio cholerae is responsible for many outbreaks of cholera in Asia, Africa, and Latin America since the 1980s. However, other outbreaks were caused by a strain derived from O1 or non-O1 strains.

Different strains of Vibrio cholerae can be transported throughout an estuary, according to a study in Chesapeake Bay. Genetic analysis showed that many genetically diverse strains occurred at a single sampling site, whereas genetically identical strains were found at several sampling sites.