3.3 Difference in Bacterial community composition
The analysis of co-occurring bacterial communities revealed the presence of 36 phyla, 88 orders, 242 classes, 413 families, 858 genera, and 1,422 species across all samples. As shown in Figure 5-a the top 10 bacterial phyla in terms of relative abundance were Proteobacteria, Bacteroidetes, Verrucomicrobia, Firmicutes, Actinobacteria, Campylobacterota, Dadabacteria, Vibrio vermicularis, Bdellovibrionota, and Desulfobacterota. The remaining 16 bacterial phyla were classified under the “other” category.
After the first MHWs, the composition of co-occurring bacterial communities was similar between the CA and HA groups. After the 5-day recovery, the relative abundance of Ascomycetes and Micrococcus warty decreased significantly, while the Mycobacterium anisopliae increased significantly in the HB group. After the second MHWs, the relative abundance of Ascomycetes and Warty Microbacteria phylum showed a significant decrease, while the Anabaena phylum exhibited a significant increase in the HC group.
At the same time, we analyzed the distribution of symbiotic microbial communities at the genus level, which is depicted in Figure 5-b. The top 15 bacterial genera in terms of relative abundance were u. Flavobacteriaceae, Marivita , u. Legionellaceae, Ruegeria ,Achromobacter , Methylotenera , Limnobacter ,Mycoplasma , Halomonas , Donghicola ,Rubritalea , u. Helicobacteraceae, u. Bacteria, Coxiella , and u. Rhizobiaceae.
Considering the relative abundance of coral symbiotic bacteria, after the first MHWs, the HA group exhibited an increase of u. Legionellaceae,Ruegeria , and Achromobacter , while a decrease of u. Flavobacteriaceae, Marivita , Methylotenera ,Limnobacter , Donghicola , and Coxiella . Following the 5-day recovery, the HB group showed an increase in the relative abundance of u. Flavobacteriaceae, u. Legionellaceae, andAchromobacter , along with a decrease of Marivita ,Ruegeria , Methylotenera , and Rubritalea . After the second MHWs, the HC group displayed an increase in the relative abundance of u. Flavobacteriaceae, u. Legionellaceae ,Achromobacter , and Halomonas , while Marivita ,Ruegeria , Methylotenera , and Rubritalea showed decreased. Finally, after the secondary 5-day recovery, the HD group exhibited an increase in the relative abundance of Rubritalea , whereas the relative abundance of u. Flavobacteriaceae, Marivita , and Ruegeria .
Fig. 5. Coral symbiotic bacterial community structure, a: histogram of community analysis at the phylum level, b: histogram of community analysis at the genus level. Unclassified species are indicated by u. (unclassified) plus the family name.