title: [Screening and identification of a microcystin-degrading bacterium strain and its enzymatic degradation of microcystin-LR by intracellular extract of Bacillus cereus].
abstract: OBJECTIVE
  To provide effective microorganisms for the treatment of water polluted by microcystins (MCs), the strains capable of biodegrading microcystin LR (MC-LR) were isolated from the sediment of Chaohu Lake. The degradation of microcystin-LR by the intracellular extracts of the strains were studied.
  
  
  METHODS
  The enrichment culture using MC-LR as the sole carbon source was utilized to isolate the microcystin-degrading strains. The isolated strain was identified according to the observation of morphology, the physiological and chemical tests and the analysis of 16S rRNA gene sequences. The degradation of MC-LR by the intracellular extracts was studied.
  
  
  RESULTS
  Strain M6 effectively degrading MC-LR was isolated and the strain M6 could grow utilizing MC-LR as the sole carbon source. Phylogenetic analysis based on 16S rRNA gene showed the similarity of 99% between strain M6 and Bacillus cereus. The experimental results suggest that the active substances for degrading MC-LR were the intracellular extracts which were the tissue enzymes of cells rather than induced enzymes. The degradation of MC-LR may be due to the catalytic effects of three enzymes. The degradation rate of 98.7% could be reached under the following conditions: pH 8.0, 404.9 mg/L of intracellular extracts, and 10 mg/L of the initial concentration of MC-LR.
  
  
  CONCLUSIONS
  Strain M6 which could biodegrade MC-LR efficiently was identified as Bacillus cereus. The influences of pH, the concentration of intracellular extracts and the initial concentration of MC-LR on the enzymatic reaction were obvious.
authors.affiliation: School of Resources and Environmental Engineering, Anhui University, Hefei 230039, China. wgy-86@163.com
authors.forename: Guangyun
authors.initials: G
authors.lastname: Wang
authors.forename: Juan
authors.initials: J
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Li
authors.forename: Rong
authors.initials: R
authors.lastname: Jia
mesh_terms: D001409:Bacillus cereus / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008387:Marine Toxins; D052998:Microcystins / Q000378:metabolism*
chemical_list: D008387:Marine Toxins; D052998:Microcystins; C057862:cyanoginosin LR