title: Biodegradation of microcystin-LR and-RR by a novel microcystin-degrading bacterium isolated from Lake Taihu.
abstract: Microcystin-LR (MC-LR) and microcystin-RR (MC-RR) are the two most common microcystins (MCs) present in fresh water posing a direct threat to public health because of their hepatotoxicity. A novel MC-degrading bacterium designated MC-LTH1 capable of degrading MC-LR and -RR was isolated, and the degradation rates and mechanisms of MC-LR and -RR for this bacterium were investigated. The bacterium was identified as Bordetella sp. and shown to possess a homologous mlrA gene responsible for degrading MCs. To the best of our knowledge, this is the first report of mlrA gene detection in Bordetella species. MC-LR and -RR were completely degraded separately at rates of 0.31 mg/(L h) and 0.17 mg/(L h). However, the degradation rates of MC-LR and -RR decreased surprisingly to 0.27 mg/(L h) and 0.12 mg/(L h), respectively, when both of them were simultaneously present. Degradation products were identified by high performance liquid chromatography coupled with time-of-flight mass spectrometry. Adda (m/z 332.2215, C20H29NO3) commonly known as a final product of MC degradation by isolated bacteria was detected as an intermediate in this study. Linearized MC-LR (m/z 1013.5638, C49H76N10O13), linearized MC-RR (m/z 1056.4970, C49H77N13O13), and tetrapeptide (m/z 615.3394, C32H46N4O8) were also detected as intermediates. These results indicate that the bacterial strain MC-LTH1 is quite efficient for the detoxification of MC-LR and MC-RR, and possesses significant bioremediation potential.
authors.affiliation: Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, 210009, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Yang
authors.forename: Yuanlong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Rongli
authors.initials: R
authors.lastname: Sun
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wei
authors.forename: Yunhui
authors.initials: Y
authors.lastname: Li
authors.forename: Lihong
authors.initials: L
authors.lastname: Yin
authors.forename: Yuepu
authors.initials: Y
authors.lastname: Pu
mesh_terms: D001427:Bacterial Toxins / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001884:Bordetella / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology; D005798:Genes, Bacterial; D007700:Kinetics; D008387:Marine Toxins; D052998:Microcystins / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D001427:Bacterial Toxins; D008387:Marine Toxins; D052998:Microcystins; D012336:RNA, Ribosomal, 16S; C063855:microcystin RR; C057862:cyanoginosin LR