Abstract：
Microcystis aeruginosa (M. aeruginosa) causes massive blooms in eutrophic freshwater and releases microcystin. Poyang Lake is the largest freshwater lake in China and has kept a mid-nutrient level in recent years. However, there is little research on microcystin production in Poyang Lake. In this study, water and sediment samples from ten sampling sites in Poyang Lake were collected from May to December in 2020, and from January to April in 2021 respectively. Microcystis genes (mcyA, mcyB, 16 s rDNA) were quantified by real-time fluorescence quantitative PCR analysis, and then the spatial and temporal variation of mcy genes, physicochemical factors, and bacterial population structure in the lake was analyzed. The relationship between the abundance of mcy genes and physicochemical factors in water column was also revealed. Results indicated that the microcystin-producing genes mcyA and mcyB showed significant differences in spatial and temporal levels as well, which is closely related to the physicochemical factors especially the water temperature (p < 0.05) and the nitrogen content (p < 0.05). The abundance of mcy genes in the sediment in December affected the abundance of mcy genes in the water column in the next year, while the toxic Microcystis would accumulate in the sediment. In addition to the toxic Microcystis, we also found a large number of non-toxic Microcystis in the water column and sediment, and the ratio of toxic to non-toxic species can also affect the toxicity production of M. aeruginosa. Overall, the results showed that M. aeruginosa toxin-producing genes in Poyang Lake distributed spatially and temporally which related to the physicochemical factors of Poyang Lake.
摘要：
铜绿微囊藻(M.铜绿假单胞菌）在富营养化的淡水中引起大量水华并释放微囊藻毒素。鄱阳湖是中国最大的淡水湖，近年来一直保持中等营养水平。然而,关于鄱阳湖微囊藻毒素生产的研究很少。在这项研究中,分别于2020年5月至12月和2021年1月至4月收集了鄱阳湖十个采样点的水和沉积物样品。微囊藻基因(mcyA，mcyB,16srDNA)通过实时荧光定量PCR分析进行定量，然后是mcy基因的时空变化，物理化学因素，并分析了湖中细菌的种群结构。还揭示了水柱中mcy基因的丰度与理化因子之间的关系。结果表明，微囊藻毒素产生基因mcyA和mcyB在时空水平上也表现出显著差异，与各理化因素密切相关,特别是与水温(p<0.05)和氮含量(p<0.05)有关。12月份沉积物中mcy基因的丰度影响了次年水柱中mcy基因的丰度,而有毒的微囊藻将在沉积物中积聚。除了有毒的微囊藻,我们还在水柱和沉积物中发现了大量无毒的微囊藻,并且有毒与无毒物种的比例也会影响铜绿分枝杆菌的毒性产生。总的来说,结果表明，鄱阳湖铜绿假单胞菌产毒基因在空间和时间上的分布与鄱阳湖的理化因子有关。
