Screening Of Quorum Sensing Bacteria From Pocillopora Damicornis Coral-symbiotic And Its Potential Mediated Roles On Coral Bleaching

Coral symbiotic bacteria are important components of coral symbiosis,which are closely related to the health of coral.However,global climate change and changeable environmental disturbances increased the pressure on coral,break the balance of coral symbiotic microbial functions,and eventually causing coral blenching or other diseases.Some pathogenic bacteria in coral symbiotic bacteria can produce quorum sensing(QS)signal molecules.When the concentration of QS signal molecule reaches a threshold value,it will cause changes in the structure and function of coral symbiotic bacteria,and then leading coral blenching.In order to better understanding the correlation between coral health status and coral symbiotic bacteria,it is important to study the difference of microbial community structure between healthy and blenched coral.However,to the best of our knowledge,there is still a lack of systematic research on the relationship between microbial diversity and coral health from quorum sensing prespective.In this work,we focused on Acropora sp.coral and collected samples from the Yinyu Island,northern Xisha Islands.Firstly,using the high-through sequencing technology,we analyiszed the differences of microbial communities between the healthy coral and blenched coral.Then,using the experimental culture,we screened the QS signal(homoserine lactone,AHL)bacteria with the report-strain(KYC55).Finally,we evaluated the roles of QS or QS strain in regulation coral blenching.The results show that:(1)the coral bleaching event reduced the diversity of coral symbiotic microbial changed the metabolic potentials of C,N,and P nutrients,and resulted in significant impact on coral symbiotic microbial communities and functional activities;(2)Total of 11 strains of QS functional bacteria were obtained from the culture of bleaching corals,including 4 strains Monomonas sp.,3 strains Vibrio sp.,2 strains Edwards sp.,1 strain Cobetia marina,and 1 strain Bacillus sp.After identified the chemical structure of QS molecules,we found that these bacteria could produce 3 kinds of AHL signal substances,namely C8-AHL,C8-OH-AHL and C10-AHL;(3)the isolated strains,including Vibrio sp.,Edwards sp.,Aeromonas sp.,Pseudomonas sp.,Bacillus sp.,Alteromonas sp.,Halomona sp.,Shewanella sp.and Roseobacter sp.have the ability to produce QS signals.The correlation analysis shown that these bacteria contributed to 67% roles to coral bleaching,indicated the coral bleaching was regulated by QS molecules.Therefore,the QS functional bacteria in coral symbiotic mediate and aggravate coral bleaching.This study clarifies the difference of microbial communities between the healthy coral and blenched individual,reveals the quorum sensing signal characteristics in coral symbiotic.At the same time,This work can provides theoretical basis for understanding the blenching mechanism of coral from quorum sensing perspective.It can also help us to develop some new methods(such as quorum sensing inhibitors)to protect coral under environmental stress.