Studies on luminous, Vibrio harveyi associated with shrimp culture system rearing Penaeus monodon.

Microbiological studies in a modified extensive shrimp culture system at Nambuthalai, southeast coast of India were carried out for a period of 120 days. Population dynamics and distribution profile of luminous bacteria and total heterotrophic bacteria in the water, sediment and animal samples were monitored. Luminous bacteria associated with exoskeleton, gills and gut were isolated and quantified. The total heterotrophic bacterial counts ranged from 1.3 x 104 to 25.3 x 104 CFU ml-1 in water and 1.5 x 106 to 26.2 x 106 CFU g-1 in sediment. The V. harveyi population density varied between 0.6 x 104 and 8.8 x 104 LCFU ml-1 in water and from 1.2 x 106 to10.4 x 106 LCFU g-1 sediment respectively. The gut of the animal was found to harbor high density of V. harveyi than gills and exoskeleton. The total heterotrophic bacteria and V. harveyi population density showed increasing trend during the culture period. The high V. harveyi density observed in this study at the end of the culture period correlated with the outbreak of white spot disease.

Physico-chemical and microbial characteristics of the coral reef environment of the Gulf of Mannar marine biosphere reserve, India.

Investigation on physico-chemical parameters and bacteial characteristics of the coral reef environs of the Gulf of Mannar biosphere reserve was studied. The study found the influence of different physico-chemical parameters on one another and also on the distribution of the total heterotrophic bacteria (THB) in the coral reef areas. Nutrients exhibited considerable seasonal and spatial variations with influence on the bacterial population. Coral reef areas recorded higher bacterial population density both in water (3.5 to 18 x 10(5) CFU ml(-1)) and sediment (1 to 14 x 10(7) CFU g(-1)) samples than the non coral reef areas (3.4 to 10.5 x 10(4) CFU ml(-1) in water and 0.9 to 7 x 10(6) CFU g(-1)). The study also found the dominance of gram negative groups at all the three stations (64.73, 63,5 and 72.59%) with Pseudomonas contributing maximum number of strains in all the samples. In addition Vibrio, Aeromonas, Flavobacterium, Cytophaga, Enterobacter and Alcaligenes were also recorded. The gram positive group was represented by Bacillus, Micrococcus, Arthrobacter and Corynebacterium. The genetic composition of THB isolated from the coral mucus revealed the presence of Vibrio and Micrococcus in all the coral mucus.