Genome analysis of the coral bleaching pathogen Vibrio shiloi.
Journal - Archives of microbiology (Germany )
The past few decades have seen a world-wide increase in coral diseases, yet little is known about coral pathogens. In this study, techniques commonly used in pathogenomic research were applied to the coral pathogen Vibrio shiloi in order to identify genetic elements involved in its virulence. Suppressive subtractive hybridization was used to compare the gene content of V. shiloi to that of a closely related but non-pathogenic bacterium, Vibrio mediterranei, resulting in identification of several putative virulence factors and of three novel genomic islands. The entire genome of V. shiloi was further screened for genes related to previously characterized steps in infection: adhesion, superoxide dismutase production and toxin production. Exposure of pure cultures of V. shiloi to crushed coral tissues strongly affected the expression of seven genes encoding pili, zona occludins toxin (Zot) and a superoxide dismutase. Analysis of eight V. shiloi strains isolated in the last decade shows a shift of the natural population from strains carrying all three genomic islands to strains carrying none of them. This shift occurred following appearance of resistance in the coral Oculina patagonica to infection by V. shiloi. The relevance of these findings to the bleaching disease caused by V. shiloi is discussed.
|ISSN : ||0302-8933|
|Mesh Heading : ||Adhesins, Bacterial Animals Anthozoa Bacterial Proteins Bacterial Toxins Genomic Islands Molecular Sequence Data Nucleic Acid Hybridization Open Reading Frames Operon Vibrio Virulence Factors genetics metabolism genetics metabolism genetics metabolism isolation & purification metabolism genetics metabolism|
|Mesh Heading Relevant : ||Genome, Bacterial microbiology genetics|
The coral probiotic hypothesis.
Journal - Environmental microbiology (England )
Emerging diseases have been responsible for the death of about 30% of corals worldwide during the last 30 years. Coral biologists have predicted that by 2050 most of the world's coral reefs will be destroyed. This prediction is based on the assumption that corals can not adapt rapidly enough to environmental stress-related conditions and emerging diseases. Our recent studies of the Vibrio shiloi/Oculina patagonica model system of the coral bleaching disease indicate that corals can indeed adapt rapidly to changing environmental conditions by altering their population of symbiotic bacteria. These studies have led us to propose the Coral Probiotic Hypothesis. This hypothesis posits that a dynamic relationship exists between symbiotic microorganisms and environmental conditions which brings about the selection of the most advantageous coral holobiont. Changing their microbial partners would allow the corals to adapt to changing environmental conditions more rapidly (days to weeks) than via mutation and selection (many years). An important outcome of the Probiotic Hypothesis would be development of resistance of the coral holobiont to diseases. The following evidence supports this hypothesis: (i) Corals contain a large and diverse bacterial population associated with their mucus and tissues; (ii) the coral-associated bacterial population undergoes a rapid change when environmental conditions are altered; and (iii) although lacking an adaptive immune system (no antibodies), corals can develop resistance to pathogens. The Coral Probiotic Hypothesis may help explain the evolutionary success of corals and moderate the predictions of their demise.
|ISSN : ||1462-2912|
|Mesh Heading : ||Animals Anthozoa Bacteria Ecosystem Evolution Immunity, Innate Seawater Symbiosis growth & development growth & development microbiology|
|Mesh Heading Relevant : ||Adaptation, Physiological Probiotics microbiology physiology|