Comparative study of gut content microbiota in freshwater fish with different feeding habits: A case study of an urban lake.

The gut microbiota plays a crucial role in various physiological functions of the host and can be modulated by numerous factors, including feeding habit or trophic level. In this study, the impact of host feeding habits on the gut microbiota of freshwater fish was explored. Ten fish species, classified into four feeding habit categories (herbivorous, omnivorous, planktivorous, and carnivorous) were sampled from West Lake, a renowned urban scenic lake, and their gut content microbiota was analysed using 16S ribosomal RNA gene sequencing. A total of 2531 operational taxonomic units, belonging to 34 bacterial phyla, were identified, with 33.4% shared across all feeding habits. Firmicutes and Proteobacteria were the predominant phyla. However, at the family level, Peptostreptococcaceae and Clostridiaceae_1 were the most dominant. Microbiota composition diversity was highest in herbivorous fish, followed by omnivores, carnivores, and planktivores. Statistically significant differences in microbiota diversity were found between different feeding categories, except for the omnivores, which did not differ from the carnivores or planktivores. The most abundant predicted metabolic pathways across all feeding habits were similar, with amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, and metabolism of other amino acids being dominant. However, comparing the relative abundance of gene functions between different feeding habits revealed notable variations across most comparisons. Co-occurrence network analysis for each feeding habit revealed that all networks were dominated by the strong positive correlation among pairs of bacterial genera abundances, while the basic properties varied, implying differences in gut microbiota interactions based on the feeding habit. In conclusion, these results confirmed that the feeding habit could affect the structure and composition of the gut content microbiota but also changed their functions and interactions.