Anything interest, or give any comment?? Cholera is a vibrio cholerae bacterium

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Anything interest, or give any comment??

Cholera is a vibrio cholerae bacterium caused by poor sanitation techniques in water; which was first isolated in 1992 and by 1993 had been discovered throughout the Indian subcontinent. This outbreak occurence resulted from a single source after a horizontal gene transfer (HGT) subsituted the serotype of an epidemic V.cholerae 01 E1 to strain 0139. Horizontal gene transfer is the movement of a genetic material between unicellular or multicelluar organism other than by the vertical transmission of DNA from parent to offspring. This trasnmission of DNA occurs in cholera. Now that this newly obtained DNA is integrated into the genome of V.cholerae, recombination has taken place. Recombination essentially is the regrouping of genes, particularly by the crossing over in chromosomes or by the artifical gathering of segments of DNA from different organisms. V.cholera home is located in the aquatic enviornment as well as in the lumen of the intestine of humans. This bacteria responds to change in their enviornment by modulating gene expression of regulatory genes and virulence factors. Extensive molecular and genetic analysis has led in recent years to the elucidation of events in the pathogenesis of cholera. Cholera toxin (CT) and toxin-corregulated pili (TCP) are considered to be the most important virulence factors, while CT is responsible for diarrhea, TCP helps the vibrios to colonize the intestine.

Explanation / Answer

The main reservoirs of V.Cholerae are people and aquatic sourcessuch acopes brackish water and estuaries,often in association with copepodsor other zooplanktons,shellfish and aquatic plants.

Cholera infections are most commonly acquired from drinking water in which V. cholerae is found naturally or into which it has been introducedfrom the faeces of an infected person.

Nonpathogenic strains are also present in water ecologies. Gene transfer is fairly common amongst bacteria, recombination of different V. cholerae genes can lead to new virulent strains.

Bacteriophage CT isa filamentous phage that contains the genes for cholera toxin. Infectious CT particles are produced when V.Cholerae infects humans. Phage particlesare secreted from bacterial cells without lysis. When CTX infects V.Cholerae cells, it integrates into specific sites on either chromosomes. CTX contains eight genes involved in phage reproduction , packaging, secretion, integration and regulation.

While TCP is a large genetic elementflanked by two repetitive regions,resembling a phage genome in structure.

Natural genetic transformation

V.Cholerae can be induced to become competent for natural genetic transformation when grown on chitin, a biopolymer that is abundant in aquatic habitats. It is a sexual process involving DNA transfer from one bacterial cell to another through the intervening medium and the integration of the donor sequence into the receipient genome by homologous recombination .

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