Differences in composition of microbial between healthy swamp eels（italicMonopterus albus/italic）and swamp eels lying on water grass

Objective The This study aims to uncover the differences in the microbiota composition of healthy and water grass-lying eels,thus providing reference for preventing diseases of swamp eel farming. Method Water(HW,BW),body surface mucus(HN,BN),and intestinal mucosa(HC,BC)from healthy and water grass-lying eels were collected as experimental materials.The microbial community structure was analyzed through Illumina high-throughput sequencing. Result (1)Water grass-lying eels reduced the Alpha diversity of microbial communities.Among them,the Alpha diversity of the HN group was the highest,which was significantly higher than that of the BN group(PProteobacteria and Firmicutes,while the abundance of Bacteroidetes and Fusobacteria decreased.At the genus level,there was an increase in the abundance of genera such as Aeromonas,Chryseobacterium,Flavobacterium,Lactococcus,Undibacterium,and Achromobacter,and a decrease in the abundance of genera like Cetobacterium,Pedobacter,Emticicia,Polynucleobacter and so on.(3)LefSe analysis identified dominant differential species in the HN and HC groups as belonging to the genera Cetobacterium and Plesiomonas.The BN group's dominant differential species were mainly Flavobacterium,Chryseobacterium,Aeromonas,and Undibacterium.The BC group's dominant differential species included Pseudomonas,Achromobacter,Acidovorax,and Lactococcus.The relative abundance of Aeromonas showed a gradual decrease from water to body surface mucus to intestinal mucosa in both healthy and water grass-lying eels,while the genus Cetobacterium was mainly enriched in the body surface mucus and intestinal mucosa of healthy eels.(4)The functional prediction results indicated that the pathogenicity and stress tolerance phenotype flora of water grass-lying eels were higher than those of healthy eels,and the main involvement is the flora of phylum Proteobacteria. Conclusion This study represents the first analysis from a microbial ecology perspective on the interrelationships between the microbiota of aquaculture water,body surface mucus,intestinal mucosa,and the grass-lying behavior of eels.The research findings indicate significant differences in the microbial community structures of aquaculture water,body surface mucus,and intestinal mucosa between healthy and water grass-lying eels.Healthy eels exhibit higher microbial diversity with a higher abundance of beneficial bacteria,such as those belonging to the Cetobacterium,while water grass-lying eels show lower microbial diversity,accompanied by a significant increase in the abundance of potential pathogenic bacteria,such as Aeromonas from the Proteobacteria phylum.This suggests that Aeromonas and Cetobacterium could be considered as candidate microbial markers for swamp eel water grass-lying behavior.