The present study was conducted to study the composition of gut microbiome in the advanced fingerling and fingerling stage of striped pangasius catfish and catla during healthy and diseased conditions. Healthy pangasius and catla fishes were obtained from commercial farms and injected with the LD₅₀ dose of A. hydrophila. The intestinal samples from the control and injected group were collected and pooled for 16 s metagenomic analysis. Community analysis was performed by targeting the 16 s rRNA gene to explore and compare the gut microbiota composition of these fishes. The operational taxonomic units (OTUs) consisted of four major phyla: Bacteroidia, Proteobacteria, Firmicutes, and Actinobacteria. Alpha and beta diversity indices were carried out to understand the diversity of microbes within and between a sample. While comparing the advanced fingerling and fingerling stage gut microbiome of Pangasius catfish, the dominance of Proteobacteria was found in fingerlings, whereas Firmicutes and Bacteroides were found in advanced fingerlings. In catla, Proteobacteria and Bacteroides were predominant. Taxonomic abundance of the microbiota in control and diseased Pangasius and catla fishes at phylum, class, order, family, genus, and species levels were also depicted. The present study is the first of its kind, and it will help to identify the diversity of novel potential bacterial species involved in disease protection of fishes. It can lead to the development of sustainable prophylactic measures against (re-)emerging bacterial diseases in aquaculture.

本研究旨在研究健康和患病条件下条纹巴沙鱼和喀拉鲶鱼晚期鱼种和鱼种阶段肠道微生物组的组成。健康的鲶鱼和喀拉鱼是从商业养殖场获得的，并注射了 LD ₅₀剂量的嗜水气单胞菌。收集并合并对照组和注射组的肠道样本，进行 16 秒宏基因组分析。通过针对 16 s rRNA 基因进行群落分析，以探索和比较这些鱼类的肠道微生物群组成。操作分类单位（OTU）由四个主要门组成：拟杆菌门、变形菌门、厚壁菌门和放线菌门。进行α和β多样性指数是为了了解样品内部和样品之间微生物的多样性。在比较鲶鱼的高级鱼种和鱼种阶段肠道微生物组时，发现鱼种中变形菌门占主导地位，而高级鱼种中发现厚壁菌门和拟杆菌门。在卡特拉中，变形菌门和拟杆菌门占主导地位。还描述了对照鱼和患病巴沙鱼和喀拉鱼中微生物群在门、纲、目、科、属和种水平上的分类丰度。本研究是此类研究中的第一项，它将有助于确定参与鱼类疾病保护的新型潜在细菌物种的多样性。它可以导致针对水产养殖中（重新）出现的细菌性疾病制定可持续的预防措施。