Viridiana Avila-Magaña, former student at Penn State, and team tracked genes that have already diverged in expression across species in response to any given stimuli -- in our case heat stress. She is currently a postdoctoral fellow at Colorado University Boulder.
The entire holobiont -- the coral animal, photosymbiont and microbiome -- is involved in the stress response. They found several genes that aid a coral’s response to heat stress. They also found more tolerant species had greater bacterial activity and diversity, according to Science Daily. The microbiome includes bacteria, fungi and viruses.
Among the three coral species examined - mountainous star coral, the knobby brain coral, and the starlet coral - the starlet coral was found to be more heat stress tolerant. This is due in part to a higher number and diversity of thermally tolerant microbes in their microbiomes, according to the Science Daily article.