Stress response
Bacterial stress response genes in the coral SML metagenomes were not affected by heat stress (Fig. 3A). Metagenomics describes the relative abundance of genes in the microbiome which identifies functional genes that are potentially being selected by the microbiome under those conditions (Dinsdale et al. 2008a; Coelho et al. 2022) and it does not measure which functional genes are being expressed at the point the sample was taken. Therefore, bacterial stress response gene expression could be increased under heat stress, although the metagenomes show that they are potentially not being selected by the coral SML microbiome over the experiment to respond to stress. Future studies coupling metagenomics to metatranscriptomics could elucidate the changes in stress response genes in the coral microbiome under heat stress. However, our metagenomes showed that bacterial genes related to nitrogen and sulfur metabolism strongly responded to heat stress and were potentially selected in the coral SML microbiome of P. strigosa .