Autoinducer-2 promotes microbial degradation of microcystin-LR by Leuconostoc mesenteroides BSH-02

Microcystin-LRs (MC-LR) produced by harmful cyanobacterial blooms (HCBs) pose significant hepatotoxic risks to both the environment and public health. Despite the identification and characterization of a limited number of MC-LR degrading bacteria, the challenge of safely removing MC-LRs from freshwater systems without disrupting aquatic ecosystems remains substantial. This study focused on the isolation of lactic acid bacteria from Bapshikhe, a traditional Korean fermented food, and investigated the mechanisms underlying the degradation of MC-LRs by these bacteria. This study also tested the hypothesis that cell wall-associated proteinases in probiotic bacteria play crucial roles in the degradation process. In addition, we verified the hypothesis that the MC-LR degradation mechanism of lactic is correlated with AI-2, a QS-inducing factor. MC-LR degrading bacteria, BSH-02, were successfully isolated from Bapshike, a Korean traditional fermented food, and identified by phylogenetic analysis as Leuconostoc mesenteroides. The BSH-02 strain effectively suppressed cyanobacterial blooms and degraded MC-LR. Ethylenediaminetetraacetic Acid (EDTA), a primary proteinase inhibitor of the BSH-02 strain, reduced the rate of microcystin removal. Based on these studies, the MC-degrading mechanism of BSH-02 was found to involve a metallopeptidase, aligning with mechanisms previously described in other studies. In addition, a correlation between metallopeptidases and AI-2 was identified using RT-qPCR. To the best of our knowledge, this is the first report of Leuconostoc mesenteroides degrading MC-LR. These findings suggest that Leuconostoc mesenteroides strain BSH-02 has high potential for the bioremediation of MC LR-contaminated water bodies.