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Microcystin-leucine-arginine (MC-LR), a cyclic potentially carcinogenic hepatotoxin, occurs frequently in aquatic habitats worldwide and seriously threatens ecosystem and public health. Limited effectiveness of physicochemical treatments to remove MC-LR from drinking water has led to a search for alternative cost-effective and environment friendly biodegradation strategies. Obtaining MC-degrading bacteria and understanding their MC-degrading mechanisms are outstanding challenges. Here, a novel indigenous bacterium named Sphingopyxis sp. YF1 with a high efficient capacity for MC-degradation was successfully isolated from eutrophic Lake Taihu. Through integrating mass spectrometer and multi-omics analyses accompanied by functional verification of certain genes and proteins, a complete MC-degradation pathway was firstly identified, in which MC-LR was sequentially degraded into linearized MC-LR, tetrapeptide, Adda, phenylacetic acid, and finally potential product CO 2. Some specific proteins such as microcystinase, linearized-microcystinase, tetrapeptidease and PAAase responsible for this pathway were identified. This study pioneeringly demonstrated that MC-LR can be completely degraded through natural remediation processes and revealed a significant potential for MC-LR biodegradation in both natural environment and engineered systems. Image 1 • New MC-degrading genes and products were explored through a multi-omic approach. • A complete MC degradation pathway was identified. • A novel bacterium with high MC-degrading rate was isolated from Lake Taihu. • Proteomics data of MC-degrading bacteria were obtained for the first time. • A series of key enzymes responsible for detoxifying MC-LR were identified. [ABSTRACT FROM AUTHOR]

A label-free electrochemical biosensor was fabricated based on MWCNT-COOH modified electrodes and degrading enzyme MlrB as recognition element for detecting L-MC-LR. [Display omitted] • Application of degradation enzyme MlrB as innovative recognition element. • Improvement of electrode conductivity with MWCNT-COOH functionalization. • A wide linear range (1 pg/mL ∼ 100 ng/mL) and an outstanding LOD (0.127 pg/mL). • Good sensitivity and reliability of biosensor when applied to actual water samples. A label-free electrochemical biosensor was firstly constructed to detect linear microcystin-LR (L-MC-LR) with high sensitivity. Degradation enzyme MlrB was used as recognition element for specific recognition of L-MC-LR. The electrode was modified with –COOH functionalized multi-walled carbon nanotube to increase the specific surface area and improve the conductivity, which was then applied to immobilize MlrB. The electrochemical signal was changed with the reaction between MlrB and L-MC-LR, which was recorded by using square wave voltammetry. The electrochemical biosensor showed superior sensitivity, with a dynamic range of 1 pg/mL to 100 ng/mL and a detection limit of 0.127 pg/mL. Moreover, the fabricated electrochemical biosensor exhibited excellent specificity toward L-MC-LR in real water samples. The concentrations of spiked L-MC-LR were 0.100, 5.00, 50.0 ng/mL, and the recovery rates were 95.0–104% with relative standard deviation (RSD) of 0.900–2.30% and 74.0–93.0% with RSD of 2.30–3.50% in lake water and tap water, respectively. Furthermore, the selectivity, reproducibility, and stability demonstrated the potential of degradation enzymes as recognition element in detection of cyanotoxins. [ABSTRACT FROM AUTHOR]