The origin of cholera has been elusive, even though scientific evidence clearly shows it is a waterborne disease. However, standard bacteriological procedures for isolation of the cholera vibrio from environmental samples, including water, between epidemics generally were unsuccessful. Vibrio cholerae, a marine vibrio, requiring salt for growth, enters into a dormant, viable but nonculturable stage when conditions are unfavorable for growth and reproduction. The association of Vibrio cholerae with plankton, notably copepods, provides further evidence for the environmental origin of cholera, as well as an explanation for the sporadic and erratic occurrence of cholera epidemics. On a global scale, cholera epidemics can now be related to climate and climatic events, such as El Nino, as well as the global distribution of the plankton host. Remote sensing, with the use of satellite imagery, offers the potential for predicting conditions conducive to cholera outbreaks or epidemics.

http://science.sciencemag.org/content/sci/274/5295/2025.full.pdf

Global Climate and Infectious Disease: The Cholera Paradigm*

Strains of Vibrio cholerae, both O1 and non-O1 serovars, were found to attach to the surfaces of live copepods maintained in natural water samples collected from the Chesapeake Bay and Bangladesh environs. The specificity of attachment of V. cholerae to live copepods was confirmed by scanning electron microscopy, which revealed that the oral region and egg sac were the most heavily colonized areas of the copepods. In addition, survival of V. cholerae in water was extended in the presence of live copepods. Attachment of viable V. cholerae cells to copepods killed by exposure to -60 degrees C was not observed. Furthermore, survival of V. cholerae was not as long in the presence of dead copepods as in the live copepod system. A strain of Vibrio parahaemolyticus was also seen to attach to copepod surfaces without effect on survival of the organism in water. The attachment of vibrios to copepods was concluded to be significant since strains of other bacteria, including Pseudomonas sp. and Escherichia coli, did not adhere to live or dead copepods. Attachment of V. cholerae to live copepods is suggested to be an important factor of the ecology of this species in the aquatic environment, as well as in the epidemiology of cholera, for which V. cholerae serovar O1 is the causative agent.

Ecological relationships between Vibrio cholerae and planktonic crustacean copepods.

Chitin is the (1→4)-β-linked homopolymer of N-acetyl-D-glucosamine (Fig. 1). The individual polymer chains can be thought of as helices, as each sugar unit is inverted with respect to its neighbors. This leads to their stabilization as rigid ribbons by 03—H … 05 and 06—H … 07 hydrogen bonds. The commonest form of chitin is α-chitin. Its unit cell is of two N,N‵-diacetylchitobiose units of two chains in an antiparallel arrangement. Thus, adjacent polymer chains run in opposite directions, held together by 06—H … 06 hydrogen bonds, and the chains are held in sheets by 07 … H—N hydrogen bonds (Minke and Blackwell, 1978). This gives a statistical mixture of CH2OH orientations, equivalent to half oxygens on each residue, each forming inter- and intramolecular hydrogen bonds. This results in two types of amide groups; all are involved in the interchain C=O … H—N bonds, while half of the groups also serve as acceptors for 06—H … O=C intramolecular bonds. This extensive intermolecular hydrogen bonding leads to a very stable structure, the individual polymer chains eventually giving rise to microfibrils if allowed to crystallize (Gooday, 1983). A less common form of chitin is β-chitin, in which the unit cell is of one N,N‵diacetylchitobiose unit, giving a polymer stabilized as a rigid ribbon, as for α-chitin, by 03—H … 05 intramolecular bonds (Gardner and Blackwell, 1975). Chains are then held together in sheets by C=O … H—N hydrogen bonding of the amide groups and by the CH2OH side chains, forming intersheet hydrogen bonds to the carbonyl oxygens on the next chains (06—H … 07). This gives a structure of parallel poly-N-acetylglucosamine chains with no intersheet hydrogen bonds.

The Ecology of Chitin Degradation

Vibrio cholerae serogroup O1, the causative agent of cholera, is capable of surviving in aquatic environments for extended periods and is considered an autochthonous species in estuarine and brackish waters. These environments contain numerous elements that may affect its ecology. The studies reported here examined physical interactions between V. cholerae O1 and natural plankton populations of a geographical region in Bangladesh where cholera is an endemic disease. Results showed that four of five clinical V. cholerae O1 strains and endogenous bacterial flora were attached preferentially to zooplankton molts (exuviae) rather than to whole specimens. One strain attached in approximately equal numbers to both exuviae and whole specimens. V. cholerae O1 also attached to several phytoplankton species. The results show that V. cholerae O1 can bind to diverse plankton species collected from an area where cholera is an endemic disease, with potentially significant effects on its ecology.

/pdf/attachment-of-vibrio-cholerae-serogroup-o1-to-zooplankton-3nmjpa6fcg.pdf

Attachment of Vibrio cholerae serogroup O1 to zooplankton and phytoplankton of Bangladesh waters.

28 paginas, 2 tablas. Special Issue: Basic and Applied Aspects of Aquaculture Nutrition: Healthy Fish for Healthy Consumers. The definitive version is available at www.blackwell-synergy.com

Live feeds for early stages of fish rearing.

Little is known about the nature of bacteria associated with the surface and gut of marine copepods, either in laboratory-reared animals or in the natural environment. Nor is it known whether such animals possess a gut flora. The present report deals with studies of microorganisms isolated from healthy, laboratory-reared copepods of the species Acartia tonsa Dana, from several species of wild copepods collected from a marine or estuarine environment, and from laboratory dishes containing moribund copepods. Evidence for a unique gut flora in laboratory-reared animals is presented; the predominant bacteria were represented by the genus Vibrio. Other organisms such as Pseudomonas and Cytophaga were found less abundantly associated with the copepods and not specifically associated with the gut. Images

Bacteria associated with the surface and gut of marine copepods.

cannotbeproven.Research for the project reported here wasinitiatedonacruiseintheGulfofMexicoaboardthe U.S.N.S. MIZAR. Several species of cope-pods were collected at four different stations,including sites in the openocean, offthe conti-nental shelf, andin the Mississippi Delta. Sam-ples were also collected in the Anclote River,Tampa,Fla.; in BayboroHarbor, Bayboro, Fla.;and from copepod cultures at the Naval Re-search Laboratory, Office of Naval Research,

M. R. Sochard

Papers

Bacteria associated with the surface and gut of marine copepods.

Bacteria Associated withtheSurface andGutofMarine