Microcystins (MCs) are among the predominant cyanotoxins that are primarily degraded by heterotrophic bacteria in various freshwater environments, including Lake Erie, a Laurentian Great Lake. However, despite the prevalence of MCs in Lake Erie basins, our knowledge about the taxonomic diversity of local MC-degrading bacteria is largely limited. The current study obtained thirty-four MC-degrading bacterial pure isolates from Lake Erie surface water and characterized their taxonomical and phenotypic identities as well as their MC-degradation rates under different pH, temperature, availability of organic substrates and with other MC-degrading isolates. Obtained MC-degrading isolates included both Gram-positive (18 isolates of Actinobacteria and Firmicutes) and Gram-negative bacteria (16 isolates of Gamma-proteobacteria); and 7 of these isolates were motile, and 13 had the capacity to form biofilms. In general, MC-degradation rates of the isolates were impacted by temperature and pH but insensitive to the presence of cyanobacterial exudates. At the optimal temperature (30–35°C) and pH (7–8), individual isolates degraded MC-LR, the most abundant MC isomer, at an average of 0.20 µg/mL/hr. With additions of cyanobacterial exudates, only Pseudomonas sp. LEw-2029, a non-motile biofilm maker, showed increased MC degradation (0.25 µg/mL/hr). Five out of nine tested dual culture mixtures showed rises in MC degradation rates than their corresponding monocultures; the highest rate reached 0.40 µg/mL/hr for the pair LEw-(1132 + 2029). PCR amplification of mlrA genes yielded negative results for all isolates; subsequent enzyme assay-Mass Spectrum analysis identified no product associated with the mlr gene-based MC degradation pathway. Collectively, our results demonstrated that a diversity of indigenous Lake Erie bacteria can degrade MCs via a novel mlr-independent pathway. Obtained MC degraders, especially Pseudomonas sp. LEw-2029, may serve as candidates for the development of biological filters to remove cyanotoxins in water treatment systems.

微囊藻毒素（MCs）是主要的蓝藻毒素，主要在各种淡水环境中被异养细菌降解，包括Laurentian Great Lake伊利湖。然而，尽管伊利湖流域的MC盛行，但我们对本地MC降解细菌的分类学多样性的认识仍然十分有限。当前的研究从伊利湖地表水中获得了34种降解MC的细菌纯分离株，并表征了它们的分类学和表型特性，以及在不同pH，温度，有机底物的可用性以及其他降解MC的菌株下的MC降解率。 。获得的MC降解菌包括革兰氏阳性菌（放线菌和硬毛菌的18种菌种）和革兰氏阴性菌（γ-变形杆菌的16种菌种）。这些分离株中有7个具有运动能力，而13个具有形成生物膜的能力。通常，分离物的MC降解速率受温度和pH的影响，但对蓝细菌渗出液的存在不敏感。在最佳温度（30–35°C）和pH（7–8）下，单个分离物会降解MC-LR（MC异构体最丰富），平均降解率为0.20 µg / mL / hr。仅添加蓝细菌渗出液假单胞菌。不运动的生物膜制造商LEw-2029显示出MC降解增加（0.25 µg / mL / hr）。在测试的9种双重培养混合物中，有5种的MC降解率高于相应的单一培养。LEw-（1132 + 2029）对的最高速率达到0.40 µg / mL / hr。mlrA基因的PCR扩增对所有分离株均产生阴性结果。随后的酶分析-质谱分析未发现与基于mlr基因的MC降解途径相关的产物。总体而言，我们的结果表明，伊利湖本土细菌的多样性可以通过新型的不依赖mlr的途径降解MC 。获得MC降解剂，尤其是假单胞菌。LEw-2029可作为开发用于去除水处理系统中氰毒素的生物过滤器的候选对象。