Characterization of microcystin-LR removal process in the presence of probiotic bacteria

• Published in: Toxicon (Oxford) 2012-01, Vol.59 (1), p.171-181
• Main Authors: Nybom, S.M.K., Dziga, D., Heikkilä, J.E., Kull, T.P.J., Salminen, S.J., Meriluoto, J.A.O.
• Format: Article
• Language: English
• Subjects: Animal poisons toxicology. Antivenoms; Bacteria; Bacteriology; Bifidobacterium; Bifidobacterium - enzymology; Bifidobacterium - metabolism; Biodegradation; Biodegradation, Environmental; Biological and medical sciences; Cell Extracts - chemistry; Cell Wall - enzymology; Chromatography, High Pressure Liquid; Cyanobacteria; Degradation; Drinking water; EDTA (chelating agent); energy; Fundamental and applied biological sciences. Psychology; glucose; Inhibitors; lactic acid bacteria; Lactobacillus; Lactobacillus - enzymology; Lactobacillus - metabolism; lakes; Medical sciences; Microbiology; microcystin-LR; Microcystin-LR removal; Microcystins - chemistry; Microcystins - metabolism; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Peptide Hydrolases - physiology; Probiotic bacteria; Probiotics; Proteinase; proteinases; proteolysis; Proteolytic activity; risk; Sphingomonas; Strain; toxicity; Toxicology; Toxins
• ISSN: 0041-0101; 1879-3150
• DOI: 10.1016/j.toxicon.2011.11.008

Toxic cyanobacteria have been reported in lakes and reservoirs in several countries. The presence of toxins in drinking water creates a potential risk of toxin transference for water consumers. Besides chemical and physical methods of cyanotoxin removal from water, biodegradation methods would be useful. The aim of the current study was to identify bacterial removal mechanisms of the hepatotoxin microcystin-LR. This was studied by testing the hypothesis of enzymatic degradation of microcystin-LR in the presence of probiotic lactic acid bacterial and bifidobacterial strains and the participation of the proteolytic system of the bacteria in this process. The results suggest that extracellularly located cell-envelope proteinases are involved in the decomposition of microcystin-LR. In particular, a correlation between proteolytic activity and microcystin removal was found and both these parameters were dependent on glucose as an energy source. In addition, EDTA, which was indicated as a main inhibitor of proteinases of the investigated strain, was shown to limit the rate of microcystin removal. The removal of microcystins was shown to be different from the known microcystin-degradation pathway of Sphingomonas. 14C-labeled microcystin was not found inside the cells and bacterial cell extracts were not able to remove the toxin, which supports the involvement of extracellularly located proteinases. The results confirm the hypothesis of enzymatic degradation of microcystins in the presence of probiotic bacteria. ► Identification of probiotic bacterial removal mechanisms of microcystin-LR – hypothesis of enzymatic degradation. ► No activity against microcystin-LR present in cytosolic fraction of probiotic bacteria. ► Extracellularly located cell-envelope proteinases involved in decomposition of microcystin-LR. ► Proteinase inhibitors limit rate of microcystin removal. ► Glucose dependent correlation between proteolytic activity and microcystin removal.