The role of genus <i>Bacillus</i> in biodegradation of microcystins: Implications for the removal of cyanotoxins from tropical freshwaters

Abstract The proliferation of harmful cyanobacterial blooms poses a threat to the ecosystem and human health. Microcystins (MCs) are the most frequently detected cyanotoxin released by cyanobacteria, including Microcystis sp. Our study aimed to isolate potential MC‐degrading bacteria in Sri Lankan freshwater and determine their possible MC‐degradation pathways. Twenty‐two morphologically distinct bacterial strains from 13 freshwater bodies were isolated following the enrichment assay. MC‐biodegradation assays further confirmed the MC‐degradation potential of 21 strains, with Bacillus being the predominant genus. The strain Bacillus altitudinis BL1, isolated from Beira Lake, showed the highest efficiency in Microcystis sp. cell lysis (80%) and MC‐degradation (87%). PCR assay results confirmed the absence of mlr ABCD genes in all strains, indicating the presence of uncharacterized alternative MC‐degradation mechanisms that require further exploration. The dual functions of Microcystis sp. cell lysis and MC‐degradation in 21 strains support developing efficient bacteria‐mediated strategies to remediate microcystins and eradicate Microcystis ‐blooms in tropical freshwaters.