Saturday 31 December 2011

When chitin meets Vibrio cholerae

A review of: Pruzzo, C., Vezzulli, L. and Colwell, R. R. (2008) Global impact of Vibrio cholerae interaction with chitin. Environmental Microbiology 10(6. 1400-1410

The paper gives an in depth review of the interaction between Vibrio cholerae and chitin. This beneficial substrate-bacteria interaction is readily observed in the marine environment. This relationship is significant in microbial ecology because of the complicated and important impact it has upon the lifestyle of the bacterium. This review documents any recent discoveries as well as an evaluation of the current literature. This allows the author to draw attention to the multiple lifestyles of V. cholerae and present a global perspective on V. cholerae-chitin interactions.

V. cholerae has been a recent focus of research, with extensive investigation regarding its genetics, ecology and physiology. However, research has largely concentrated on bacterial strains that are pathogenic to humans. Chitin is one of the most abundant biopolymers to be found in nature and is suggested to be the most prevalent in the marine environment. The relationship between chitin and V. cholerae is one the most readily evaluated incidents in microbial ecology and an example of a successful bacteria-substrate connection. The interaction provides V. cholerae with various benefits which include the adaption to nutrient availability gradients in the environment, stress tolerance and protection from predators. This interaction has a significant effect upon the lifestyle of the bacterium, influencing its ecological function in nature as well as its function inside and outside a human host.

The interaction between V. cholerae and chitin can be identified at several hierarchal levels in the environment. This hierarchal scale helps to describe the influence of the interaction on a cellular, multicellular, community and ecosystem level outlining it as a biological system that spans from the cell to the global environment. The properties of the interaction characterise different hierarchical levels are all related to one another. These include physiological responses (e.g. chemotaxis, cell multiplication, induction of competence and chitin utilization), the formation of biofilms at a multicellular level and an effect upon commensal and symbiotic relationships of higher organisms in a community. These parameters combine to globally influence the cycling of biogeochemical nutrients (e.g. C and N) and the pathogenicity of humans and animals. For further detailed descriptions regarding any of the hierarchal levels mentioned here, the paper should be consulted.

The hierarchal perspective utilised in this paper helps the reader to understand the multiple lifestyles of V. cholerae. It concisely demonstrates the role of the V. cholerae-chitin connection in the environment, showing its significance on both a cellular level as well as its influence on a larger global scale. This approach advocates that the various lifestyles of V. cholerae and its pathogenicity-related properties are derived from selective environmental pressures in its primary marine habitat. It could be argued that if diligence of V. cholerae in its primary habitat is essential, then V. cholerae has been successful in acquiring the necessary adaption’s to ensure survival. This suggests that its fitness and function outside its natural environment is dependent upon its ability to acquire the crucial properties that are specific to its new habitat or environment (e.g. acquiring fundamental adaptations to survive in the human gut).

In review of the current literature, it is proposed that the processes involved with cholera in the human gut have resulted from a specific adaptation, accumulated by V. cholerae, associated in supporting osmoregulation in the host. This outlines the V.cholerae-chitin interaction, characterised at each level in the hierarchal scale, as a possible model to aid the investigation of the role of primary habitat selection in regards to the emergent pathogenicity attributes of bacteria of which the marine environment is their primary habitat. I think that this field is always going to be of interest to safe guard our global population and it may be possible to use the conclusions drawn from this paper in understanding and identifying other virulence factors in human diseases.

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