title: Microcystin-degrading bacteria affect mcyD expression and microcystin synthesis in Microcystis spp.
abstract: Cyanobacterial blooms occur increasingly often and cause ecological, economic and human health problems worldwide. Microcystins (MCs) are the dominant toxins produced by cyanobacteria and are implicated in epidemic disease and environmental problems. Extensive research has been reported on the various regulating factors, e.g., light, temperature, nutrients such as nitrogen and phosphorus, pH, iron, xenobiotics, and predators, that influence microcystin (MC) synthesis, but little is known about the effects of cyanobacteria-associated bacteria on MC synthesis. A considerable number of studies have focused on interactions between Microcystis species and their associated bacteria. In this study, we evaluated the effects of MC-degrading bacteria (MCDB) on MC synthesis gene mcyD expression and MC synthesis in axenic strain PCC7806, non-axenic strain FACHB905, and colony strain FACHB1325 of Microcystis by quantitative real-time polymerase chain reaction (RT-PCR) assay and enzyme-linked immunosorbent assay (ELISA). We demonstrate for the first time that MCDB can induce and up-regulate the MC production and transcriptional response of the mcyD gene of toxic Microcystis. On day 4 of the culturing experiment, the intracellular MC concentration and transcriptional response of mcyD of FACHB1325 were up-regulated 1.9 and 5.3-fold over that of the control, and for FACHB905 were up-regulated 1.8 and 4.2-fold over that of the control, respectively. On day 10, the transcriptional response of mcyD was up-regulated 21.3-fold in PCC7806. These results indicate that there are interactions between toxic Microcystis and MCDB, and MCDB may play a role in regulating mcyD expression in toxic Microcystis.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: zhulin0510420@126.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zuo
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: lrsong@ihb.ac.cn.
authors.forename: Lirong
authors.initials: L
authors.lastname: Song
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: gannq@ihb.ac.cn.
authors.forename: Nanqin
authors.initials: N
authors.lastname: Gan
mesh_terms: D002681:China; D015964:Gene Expression Regulation, Bacterial; D052998:Microcystins / Q000235:genetics* / Q000378:metabolism; D046931:Microcystis / Q000235:genetics* / Q000378:metabolism
chemical_list: D052998:Microcystins; C078588:microcystin
keywords: MC-degrading bacteria; Microcystins; Microcystis; mcyD gene