Opportunistic bacteria use quorum sensing to disturb coral symbiotic communities and mediate the occurrence of coral bleaching

Abstract

Coral associated microorganisms, especially some opportunistic pathogens can utilize quorum-sensing (QS) signals to affect population structure and host health. However, direct evidence about the link between coral bleaching and dysbiotic microbiomes under QS regulation was lacking. Here, using 11 opportunistic bacteria and their QS products (AHLs, acyl-homoserinelactones), we exposed Pocillopora damicornis to three different treatments: test groups (A and B: mixture of AHLs-producing bacteria and cocktail of AHLs signals respectively); control groups (C and D: group A and B with furanone added respectively); and a blank control (group E: only seawater) for 21 days. The results showed that remarkable bleaching phenomenon was observed in groups A and B. The operational taxonomic units-sequencing analysis shown that the bacterial network interactions and communities composition were significantly changed, becoming especially enhanced in the relative abundances of Vibrio, Edwardsiella, Enterobacter, Pseudomonas, and Aeromonas. Interestingly, the control groups (C and D) were found to have a limited influence upon host microbial composition and reduced bleaching susceptibility of P. damicornis. These results indicate bleaching's initiation and progression may be caused by opportunistic bacteria of resident microbes in a process under regulation by AHLs. These findings add a new dimension to our understanding of the complexity of bleaching mechanisms from a chemoecological perspective.

The Meta-Organism Response of the Environmental Generalist Pocillopora damicornis Exposed to Differential Accumulation of Heat Stress

“…Neither an increase in diversity nor an increase in pathogenic taxa was observed, both of which have been used as indicators of thermal stress. It is still equivocal whether alternative states of the coral microbiome linked to bleaching are a consequence of bleaching (Ainsworth et al, 2008) or play an active role in the development of bleaching (Zhou et al, 2020), therefore it is possible that changes (or a lack thereof) occurring at the microbial community level are offset from the photosystem health and symbiont density indicators of bleaching used in the present study. As the present study analysis was a community-level approach to quantifying the coral microbiome, it is also possible that subtle changes in the microbiome remain undetected, as do functional changes of the in hospite bacteria.…”

Coral Probiotics: Premise, Promise, Prospects

“…In Acropora cervicornis, the addition of exogenous AHLs produced symptoms similar to those of white-band disease and, in conjunction with a healthy coral homogenate, was able to act as a disease-causing agent (93). Aquarium experiments with P. damicornis also found evidence for a relationship between AHL regulation and coral-bleaching progression, because corals treated with exogenous AHLs and AHL-producing bacteria were more susceptible to bleaching and displayed more significant changes in their bacterial community compositions than control groups treated with the same substances with the addition of a QS inhibitor (94). This suggests that the inhibition of QS or the breakdown of QS autoinducers such as AHLs may be a potential BMC characteristic that protects corals from pathogens and bleaching (12,90,95).…”

Changing microbial activities during low salinity acclimation in the brown algaEctocarpus subulatus

“…Quorum sensing (QS) and AI-1, in particular, have been linked to dysbiosis in several model systems. For instance, in the coral Pocillopora, AI-1 type QS compounds have been related to coral bleaching (Zhou et al, 2020). Similarly, in Acropora, inhibitors of AI-1 have been shown to prevent white band disease (Certner and Vollmer, 2018).…”