Use of the cell quota and chlorophyll content for normalization of cylindropermopsin produced by two Cylindrospermopsis raciborskii strains grown under different light intensities

The production of cylindrospermopsin (CYN) by Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju (Cyanobacteria) was already shown to be changed by variations in light intensities. Influences of light intensity on CYN production by two different C. raciborskii strains (CYP011K and CYP030A) were studied in batch culture conditions. The strains were grown under photon light intensities from 40 to 348 μmol photons m-2 s-1. The growth rates were measured by exponential regression of cell number variation along the time. The concentration of chlorophyll-a (Chl-a) was measured by spectrophotometric methods and the CYN concentration was measured by high-performance liquid chromatographic methods. Data from these CYN analyses were evaluated as cell quota (ng CYN 10-6 cells) or as the relative proportion between toxin concentration and chlorophyll-a concentration (CYN Chl-a-1). The CYP011K showed higher growth rates than the CYP030A strains. According to the cell quota results, the production of CYN by these two strains of C. raciborskii is not affected by the intensity of the surrounding light during growth. However, analysis of the relative proportion of CYN Chl-a-1 led to different interpretations, as a negative relation between light intensity and CYN production.