Toxicogenomics and Drug Monitoring

Biography

Biography: Suvendra Nath Bagchi

Abstract

For harmful cyanobacterial blooms microcystin synthetase (mcy) genes are indicators of toxigenic genotypes producing an array of peptidal hepatotoxins, microcystins. Toxic and non-toxic blooms are likely to harbor choleragenic Vibrio cholerae, thereby substantiating and complicating the toxicological manifestation, as the symptoms, i.e. diarrhea, are common for both cyanobacterial and bacterial toxins. In present work, over 65% of Microcystis- and Oscillatoria- dominated cyanobacterial blooms collected from different locales in Central India harbored viable but non-culturable V. cholerae O1 and O139 strains, as revealed from PCR amplification of VCO1/139 antigen genes. The Vibrio association with phytoplankton was quite fragile and during washings it was released into a “free” state which passed through a 5 μm filter but was retained by 0.45 μm membrane. Though amplification of mcyABDE genes was discernable in 50% of the bloom material, indicating presence of toxigenic genotypes, only 57% of them produced microcystin, the –RR variant at 0.03-4.1 mg/g dry mass. The corresponding microcystin concentrations in lake waters were ≤60 ng L-1. Such low level of cell-bound and the dissolved microcystins is of insignificant health consequence. We believe that phytoplankton-adhered V. cholerae is a potential health threat particularly in the cholera endemic region. Release if “free” Vibrio is another concern as this may lead to spread of cholera as blooms relocate in more freshwaters. Renewed guidelines for toxic cyanobacteria should be formulated considering occurrence of pathogenic Vibrio. Moreover, in situ bacterial quantification methods using RT PCR and Fluorescence microscopy should be optimized in toxic phytoplankton material.