Studies on the microbial diversity of salted fishes under aerobic conditions

Abstract

A total of 93 isolates of halophilic and moderately halophilic bacteria were isolated from salted fishes, Scoliodon sp. and Thrissina thryssa obtained from retail fish outlets in Cochin, Kerala, India. The viable count of the bacteria in Scoliodon sp. and Thrissina thryssa ranged from 103-106 per g. The morphological, biochemical, and physiological investigations were done to characterize the isolates, which showed good growth in medium containing 3-10% NaCl at 37°C. In Scoliodon sp. the maximum of 87.5% isolates were Gram-positive cocci and in Thrissina thryssa 95.5% of the isolates were Gram-positive rods. The optimum conditions such as temperature, pH, and salts were determined. The utilization of organic compounds such as fructose, lactose, glucose, sucrose, arabinose, trehalose, maltose, salicin, mannose, cellobiose, rhamnose, dulcitol, xylose, raffinose, sorbitol, adonitol, inulin, galactose, inositol, mannitol, hydrogen sulfide, nitrate, citrate utilization, MR-VP, triple sugar iron, as well as the hydrolysis of organic compounds such as casein, gelatin, aesculin, starch, Tween 20, and Tween 80 were also investigated. Moreover, an alkalophilic bacterial strain Bacillus halodurans was isolated from Thrissina thryssa and confirmed by 16S rDNA analysis. These studies revealed that salted fishes offer an optimal environment for the viable, diverse, potentially and industrially important bacterial community.