Phylogenetic characterization of pathogenic bacterial species in diseased Channa striata (Bloch,1793) from Meghadrigedda reservoir, Visakhapatnam

Fish stocks and the sustainability of aquaculture are at serious risk from disease outbreaks. The widespread freshwater species Channa striata was farmed extensively in Southeast Asia. However, infections caused by bacteria significantly threaten their overall health and ability to support themselves financially. This study aimed to isolate and molecularly characterize bacterial strains associated with diseases in Channa striata fish samples from the Meghadrigedda reservoir in Visakhapatnam. The bacterial pathogens were identified by isolating and purifying bacterial species from the skin mucosa and by amplification, 16s rRNA gene sequencing and phylogenetic analysis. Sequence analysis revealed that 16s rRNA from purified strains such as FBP-5 and FBP-6 has total base pairs of 1499 and 1463 with corresponding GC percentages of 55.1and 54.8. BLASTn analysis revealed that FBP-5 and FBP-6 have similarities to Aeromonas and vibrio species respectively. FBP-5 has the highest similarity to Aeromonas schubertii strain CDC 2446-81 with an identity of 99.47%. BLASTn search of the 16s rRNA gene sequence of FBP-6 revealed maximum similarity to Vibrio vulnificus strain CUVET with an identity of 99.39%. Alignment of multiple sequences revealed that FBP-5 has the highest evolutionary divergence with the species of Aeromonas schubertii strain HYK2(0.7665) while FBP-6 exhibits the highest evolutionary divergence.