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.

Biodegradation of multiple microcystins and cylindrospermopsin in clarifier sludge and a drinking water source: Effects of particulate attached bacteria and phycocyanin

“…However, when it was present as the sole microcystin in the same media it was completely degraded in 24 days. These results are consistent with findings from Yang et al (2014) who investigated the biodegradation of MCLR and MCRR by a new microcystin-degrading bacterium. They reported that the isolate MC-LTH1 was able to degrade MCLR and MCRR more quickly when they were not simultaneously present.…”

Assessment of the factors contributing to the variations in microcystins biodegradability of the biofilms on a practical biological treatment facility

“…These suggested that MC-biodegradation was accompanied with the increase in MCdegrader abundance among overall bacterial community, and the degree of MC-degrader growth was positively correlated with total MCs amount. These data can be comparable to Yang et al (2013), who also showed that the MC-degrader density increased during MCs biodegradation in pure isolate culture and multiple MCs variants (MCLR plus MCRR) may act additively to promote the MC-degrader abundance. Thus, it can be inferred that all of MCLR, MCRR and MCYR were used as carbon and nitrogen sources for MCdegrader growth.…”

“…Although both separate and simultaneous MCs biodegradation have been widely conducted, so far few attempts were made to compare between the separate and simultaneous biodegradation of MCs. Only one example demonstrated that both MCLR and MCRR biodegradation rates decreased when both of them were simultaneously degraded (Yang et al, 2013). This study nonetheless indicated that there were no apparent differences in biodegradability between independent and simultaneous biodegradation of MCs.…”

Biodegradation of microcystin-LR by an amino acid-degrading anaerobic bacterium

“…, were fragment ions. The product ions were consistent with those in the ESI-MS spectra, Adda, which is identified as both of the anoxic [13] and aerobic degradation product [22,23] of MCLR. These results indicated that the intermediate degradation products of MCLR produced successively by ALA-1 under anaerobic condition were linearized MCLR, tetrapeptide and Adda.…”

“…and Bordetella sp. [12,22,23]. Furthermore, Adda has been detected as a degradation product of MCLR by anoxic sediment of Lake Dianchi [13].…”