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Microbiomes of Coral Mucus and Seawater Relate to Specific Coral Metabolic Functions

In a paper recently published in Environmental Microbiology, researchers examined the microbiome (for both taxonomy and function) in the water column as well as in the surface mucus layer (SML) of the coral Pseudodiploria strigosa. Examples derived from two distinctly different natural Bermudan coral reef environments were analyzed, including inner patch reefs (i.e., significant variation of temperature) and outer reefs (i.e., relatively stable temperature). These results demonstrate (1) how the coral microbiome can differ between these two zones and (2) potentially play a role in the health and resilience of reef corals.

Notably, this investigation reveals the importance of purple non-sulfur bacteria (PNSB) in coral metabolism at the ecosystemic level. For example, the SML microbiome of corals from outer reefs showed a relative abundance of the PNSB Rhodospirillum. Another PNSB, Rhodopseudomonas, claimed around one fourth of all the bacterial genera that encode for sulfur oxidation genes in outer coral SML; the greatest abundance in inner corals was attributed to a more evenly distributed handful of purple Proteobacteria including mainly Rhodopseudomonas, Ruegeria and Roseobacter.

Overall, this study suggests that both water column and coral mucus microhabitats of inner reef microbiomes differ from that of the less nutrient-rich, yet more stable, outer reefs. For example, among phototrophs, there was a greater abundance of cyanobacteria (e.g., Synechococcus) in both the water column and coral SML of inner reefs, whereas PNSB (Rhodospirillum in particular) dominated in the outer reefs. As the authors of this paper explain, “efforts to improve coral health by promoting or maintaining a beneficial microbiome (e.g., development of probiotics) depend on a detailed understanding of the dynamics of microbial taxa and functional profiles.”

To learn more about this study, please review:

Lima, L.F.O., Alker, A.T., Papudeshi, B. et al. Coral and Seawater Metagenomes Reveal Key Microbial Functions to Coral Health and Ecosystem Functioning Shaped at Reef Scale. Microb Ecol (2022).

To learn more about how PNSB such as Rhodopseudomonas and Rhodospirillum function in aquaria, please visit:

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