Comprehensive profiling of gut bacterial communities in hybrid red tilapia with and without streptococcosis

The gut microbiome is crucial in regulating nutrient metabolism, immune responses, and defense mechanisms against diseases. This study aimed to comprehensively compare bacterial community profiles within the foregut, midgut, and hindgut regions of red tilapia fish with and without streptococcosis. Red tilapia ( Oreochromis niloticus × Oreochromis mossambicus ) with and without streptococcosis were collected from a river cage culture farm in Central Thailand. The infected streptococcal isolates were confirmed by 16S rRNA sequencing. The 16S amplicon was sequenced in gut microbiome samples from healthy and diseased groups to analyze the bacterial composition profiles associated with red tilapia with and without streptococcosis. The alpha diversity of bacterial communities in the gut microbiome was significantly higher in the healthy group than in the diseased group. Beta diversity indicated distinct differences in bacterial communities between groups. Taxonomical profiling revealed Proteobacteria followed by Fusobacteria as the dominant phyla and Cetobacterium as the dominant genus in the gut of both groups. Linear discriminant analysis effect size indicated Vibrio , Plesiomonas , Aeromonas , Streptococcus , Chitinibacter , and Edwardsiella as relatively more abundant in the diseased group. These groups could serve as baseline populations associated with streptococcosis in red tilapia. In contrast, Romboutsia, Clostridium sensu stricto 1 , Turicibacter, Epulopiscium, Bacillus, Streptomyces, Hyphomicrobium , and Nocardioides were more abundant in the healthy group. This study provides insights into the bacterial community profiles associated with streptococcosis in the gut of red tilapia. It enhances our understanding of gut bacterial communities in red tilapia and offers a baseline perspective on bacterial populations associated with streptococcosis, which could benefit future treatment and diagnostic strategies. • Alpha and beta diversities of red tilapia with and without streptococcosis suggest differences in bacterial communities. • Vibrio , Plesiomonas , Aeromonas , and Streptococcus could serve as baseline gut populations associated with streptococcosis. • Bacillus, Streptomyces, and Cetobacterium are candidate beneficial gut microbes.