Microcystin content of Microcystis aeruginosa is modulated by nitrogen uptake rate relative to specific growth rate or carbon fixation rate

Citations Over TimeTop 10% of 2005 papers

Abstract

Modulation of microcystin production has been extensively studied in both batch and continuous cultures. Positive correlations with medium nitrogen, medium phosphorous, light intensity, inorganic carbon availability, and growth rate have been reported. Negative correlations have been reported between microcystin content and medium phosphorous. The only reported quantitative relationship between any variable and microcystin production was that of growth rate. Microcystis aeruginosa PCC7806 was therefore cultured under continuous culture conditions in a bubble-lift reactor at a growth rate of 0.01 h(-1) in modified BG11 (constant phosphate concentration of 0.195 mM and varying nitrate from 0.125 to 18 mM) and sampled at steady states for analysis of cell number, microcystin content, cellular N and P, residual medium nutrient concentration, and carbon fixation rate. Cellular microcystin quotas showed significant positive correlation with both nitrate uptake and cellular nitrogen content and were negatively correlated with carbon fixation rate, phosphate uptake, and cellular phosphorous. Thus, the ratio of nitrate uptake to phosphate uptake, cellular N to cellular P, and nitrate uptake to carbon fixation were positively correlated to cellular microcystin. Microcystin quotas increased 10-fold from the lowest to the highest steady-state values. Cellular microcystin content therefore is controlled to a significant extent by variables other than growth rate, as was previously reported, with nitrogen the most significant modulator. Batch culture in BG11 under identical conditions yielded increased microcystin when nitrogen uptake exceeded relative growth rate, confirming the importance of nitrogen uptake in the modulation of microcystin content for a specific growth rate.

Related Papers

• → Quantification of Toxic Microcystis and Evaluation of Its Dominance Ratio in Blooms Using Real-Time PCR(2008)98 cited
• → The dynamics of toxic Microcystis strains and microcystin production in two hypertrofic South African reservoirs(2012)68 cited
• → Quantification of microcystin-producing and non-microcystin producing Microcystis populations during the 2009 and 2010 blooms in Lake Taihu using quantitative real-time PCR(2012)33 cited
• → Dynamic characteristics of total and microcystin-producing Microcystis in a large deep reservoir(2023)16 cited
• → A Field Study to Investigate Environmental Factors that Could Effect Microcystin Synthesis of a Microcystis Population in the Bautzen Reservoir(1996)45 cited