3.5 | Abundance and composition of microbiota at phyla, genera and species levels
A total of 37 phyla were obtained from all fish species (Supplementary Figure 1S). We then selected the most abundant phyla with above 5%. We obtained nine phyla classified as Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria phyla with relatively high abundance, representing 66.60%, 9.82%, 9.04% and 5.18%, respectively (Figure 4). Herbivorous fish species had significantly lower abundance of Proteobacteria phylum than carnivorous and filter-feeding species (p < .05). On the contrary, herbivorous fish species had significantly higher abundance of Firmicutes and Bacteroides phyla than omnivorous, filter-feeder and carnivorous species (p< .05). The omnivorous fish species had significantly higher abundance of Verrucomicrobia phylum than omnivorous, filter-feeder and herbivorous species (p < .05).
A total of 324 bacterial genera were obtained. We then removed unidentified bacterial genera, and others and selected only those with more than 0.5% abundance. The results on composition showed 45 bacterial genera were obtained (Supplementary Figure 2S). The four fish species with different feeding habits had distinct microbiota composition at genera for the nine phyla. Carnivorous and filter-feeder species were dominated with Limnobacter species (25.05% and 23.56%) and Pseudomonas species (26.07% and 8.16%), respectively. The microbiota of omnivorous species was mainly composed of Rhodobacter species (14.99%), Zymomonas species (10.63%), Clavibacter species (8.57%) and Luteolibacterspecies (6.68%). The herbivorous fish species was mainly composed ofBacteroides species (22.56%) and Citrobacter species (9.43%).
We obtained 14 genera with significant differences in abundance of microbiota (Table 3). The carnivorous fish species had significant higher Acinetobacter species than the other three fish species (p < .05). The omnivorous fish species had higher abundance of Anaerospora , Arenimonas ,Dechloromonas , Deefgea , Luteolibacter andZymomonas genera than herbivorous and carnivorous fish species (p < .05). The herbivorous fish species had significantly higher Bacteroides genus than omnivorous, carnivorous and filter feeder fish species (p < .05).Escherichia , Limnobacter and Mycoplana genera were abundant flora of filter-feeder and carnivorous fish species, whilePseudomonas genus was abundant flora of filter-feeder and omnivorous fish species.
A total of 2048 species of bacteria were obtained. Pseudomonas stutzeri , Escherichia coli and Acinetobacter lwoffii were the most abundant species (Figure 5). The Acinetobacter johnsonii , Acinetobacter lwoffii , Escherichia coli andPseudomonas stutzeri had significant different abundance among omnivorous, herbivorous, filter-feeder and carnivorous fish species (p < .05). The carnivorous fish species had significantly higher Acinetobacter johnsonii , Acinetobacter lwoffii and Pseudomonas stutzeri than the other three fish species (p < .05). The filter-feeder and carnivorous fish species had significantly higher Escherichia coli than omnivorous and herbivorous fish species.