16S RRNA PROFILING OF THE GUT MICROFLORA IN EUTHYNNUS AFFINIS AND THUNNUS ALBACARES COLLECTED FROM THE SOUTHERN PART OF INDIA

Abstract

The intestinal microflora of fishes is essential for digestion, absorption of nutrients, immunity, and general well-being of the hosts. Gut microbiota composition depends on both host and environmental conditions. It greatly contributes to fish physiology and adaptation. This study focused on determining the bacterial diversity of two economically relevant tuna fish species, i.e., Euthynnus affinis (Kawakawa) and Thunnus albacares (Yellowfin tuna) that were sourced from different geographic regions of the south-west coast of India, which includes Thoothoor, Kanyakumari, and Trivandrum. Intestinal tissue was dissected aseptically, homogenized, serially diluted, and inoculated in Nutrient Agar plates for isolation of bacteria. Isolates were then subjected to DNA extraction and 16S rRNA PCR amplification followed by Sanger sequencing. The six isolated bacteria included Microbacterium sp. and Bacillus cereus (Trivandrum), Bacillus cereus and Lacrimispora amygdalina (Thoothoor), and Escherichia coli and Oceanisphaera ostreae (Kanyakumari). The results offer baseline information regarding composition of the gut microbiota associated with E. affinis and T. albacares from the Indian south coast and also provide knowledge on host-microbe relationships in natural environments.