Enhanced control ability against cyanobacteria through combinations of multiple algicidal bacterial strains

Algicidal bacteria are promising microorganisms for controlling harmful algal blooms (HABs) because of their ability to inhibit algal growth or lyse algal cells in aquatic systems. However, our understanding of how to enhance their performance within complex microbial communities remains limited. In this study, we evaluated the algicidal activity of previously isolated bacterial strains in a constructed cyanobacterial consortium dominated by Microcystis aeruginosa and containing indigenous lake microorganisms. Our results revealed that while individual strains generally showed limited inhibitory effects, certain strain combinations exhibited pronounced algicidal activity. Notably, co-inoculation of strain Chromobacterium sp. MERYL1-35 and strain Paucibacter sp. MERXLGS1 achieved the highest algicidal efficiency among the tested treatments. Growth assays and quantitative proteomic analysis demonstrated that these two strains establish a distinct antagonistic interspecies interaction, where Chromobacterium exerts strong inhibitory effects on Paucibacter , accompanied by significant expression alterations in certain bacterial virulence and interaction-associated proteins. We propose that this collective enhancement in population survivability and antagonistic potential of Chromobacterium substantially contributes to the enhanced algicidal activity in the dual-strain system. These findings provide new insights into the ability-enhancing strategy of algicidal bacteria and their complex interactions with target cyanobacteria. IMPORTANCE Eco-friendly and sustainable control methods of harmful algal blooms (HABs) have been urgently needed in recent years. In this study, we demonstrated that the removal efficiency of cyanobacteria by algicidal bacteria can be substantially enhanced through designed co-inoculation strategies. We found that the enhanced algicidal activity of the combined Chromobacterium and Paucibacter dual-strain inoculations is mediated by a unique antagonistic interaction, which differs from other consortia that more likely arise from cooperative strain interactions. These findings advance our understanding of the complex microbial interplay between algicidal bacteria and phytoplankton and may provide new insights into the development of biological control strategies targeting HABs.