Relative abundance of halophilic archaea and bacteria in diverse salt-fermented fish products

Abstract

Fermented fish that contain over 20% salt are expected to harbor extremely halophilic microorganisms. In the present study, salt-fermented fish samples (n = 105) which included fermented Indian shad, mackerel, anchovies, seer fish, pomfret and others collected from different locations in India were analyzed for the presence of extremely halophilic microorganisms using culture methods. The salt (NaCl) content in majority of the products was over 20% and the moisture content ranged from 28 to 57%. Three different halophilic media, each with 20 and 25% salt, were used for the enumeration and isolation of halophilic archaea and bacteria. Of 1635 isolates obtained from different media, 1198 and 437 were confirmed to be halophilic archaea and bacteria, respectively using 16S rRNA genes-specific PCR. Overall, archaea and bacteria represented 74.5% and 25.4% of the total halophilic microbial communities, respectively suggesting the predominance of archaea across a wide range of fermented fish products. The results of this study emphasize that the halophilic archaea have a dominant role in the fermentation process of fish and may contribute significantly to flavor, health benefits and bioactivities associated with fermented fish products.