Regulatory effects of the C6-HSL signal molecule and quorum quenching on marine Synechococcus in the bacteria-algal system
This study aimed to explore the regulatory effects of N-hexanoyl-L-homoserine lactone(C6-HSL)signal and quorum quenching on the growth and algal-bacterial interactions of marine Synechococcus.Enriched culture samples of Synechococcus were collected from surface waters of the central South Yellow Sea.Flow cytometry and high-throughput sequencing were used to analyze cell abundance and microbial community composition.Further-more,microbial co-occurrence networks were constructed to assess the influence of C6-HSL on the extent of mi-crobial interactions in the culture system.The results revealed that the growth of Synechococcus was significantly enhanced by C6-HSL,with its abundance in the experimental group being approximately 1.83 times higher than that in the control group after a 7-day cultivation period.However,no significant effect was observed on heterotrophic bacterial growth.C6-HSL signals altered the composition of bacterial communities within the culture system,thereby increasing the proportion of Rhodobacteraceae and Thalassospira in alpha-proteobacteria and decreasing the proportion of Marinobacter in gamma-proteobacteria.The addition of C6-HSL reduced microbial interactions and network tightness.Six strains exhibiting C6-HSL quenching activity were isolated from Synechococcus culture samples,of which five were identified as Proteobacteria and one as Firmicutes.These strains achieved quor-um-quenching activity through the intracellular pathway.The bacteria displaying quorum-quenching activity pro-moted Synechococcus growth,with stronger effects observed for those with higher quorum-quenching activity.This study elucidated the regulatory effects of quorum-sensing C6-HSL signal and bacterial quorum-quenching ability on the interaction between Synechococcus and symbiotic bacteria,providing a scientific basis for further investigation into algal-bacterial interactions.
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