3.5 Core microbiological analysis
In order to examine the changes in symbiotic bacteria within corals, a
total of 24 samples from the two MHWs treatments were analyzed. The
distribution of core operational taxonomic units (OTUs) was assessed,
and a total of 28 core OTUs were identified (Fig. 7a). At the genus
level, the distribution of these core OTUs is depicted in Figure 7-b: u.
Flavobacteriaceae (23.58 %), Marivita (9.43 %), Ruegeria(5.92 %), u. Legionellaceae (5.90 %), Achromobacter (3.95 %),
u. Methylotenera (2.12 %), Limnobacter (1.60 %),Rubritalea (1.43 %), Mycoplasma (1.38 %),Donghicola (1.30 %), u. Bacteria (1.21 %), u. Helicobacteraceae
(1.18 %), u. Dadabacteriales (1.03 %), and Coxiella (1.00 %),
indicating their dominant presence within the core OTUs.
As shown in Figure 7-c, the core OTUs species-level microbial relative
abundance expression heat map was constructed based on the top 30
species with average abundance. we can find that, Leisingera
caerulea exhibited an increase in the HA group. while the HB group
displayed an increase in u. Leptospira, Halomonas desiderata , and
u. Flavobacteriaceae. After the second MWHs, the HC group exhibited
elevated levels of u. Flavobacteriaceae, u. Coxiella, Halomonas
desiderata , and Achromobacter arsenitoxydans . After 5 days of
recovery, the HD group demonstrated a significant increase in the
relative abundance of Rubritalea tangerina , u. Dadabacteriales,
u. Woeseia, uncultured delta proteobacterium , u. Actinomarinales,
and u. DEV007 bacteria.
These results suggest that the MHWs would lead to significant
differences in coral-symbiotic microbial communities, and the core
microbial communities would be different between the two heatwaves and
the recovery period.
Fig.7. Core bacterial community structure, a: Venn diagram of
differences in community structure at the OTU level. b: Pie chart of
community analysis at the genus level of core bacteria, with bacteria
less than 1% of the genus level classified as others. c: Heat map of
community analysis at the genus level of core bacteria. Those not
identified to genus level are indicated by u. (unclassified) plus family
name.