Long, Benedict2015-12-101568-9883http://hdl.handle.net/1885/63770Microcystins (MCs) are highly toxic, non-ribosomal cyclic peptides produced by cyanobacteria. A wide range of environmental factors are known to affect MC production, yet the roles these factors play in MC metabolism are poorly understood. In this study a physiological role for sulfur in MC synthesis is proposed. Rates of amino acid and MC-LR production were determined from N-limited chemostat grown cells of the toxic cyanobacterium Microcystis aeruginosa MASH-01A19. Cluster analysis of these rates indicated a correlation between the rates of methionine and MC-LR production, suggesting that a competitive physiological requirement for this sulfur-containing metabolite may limit MC-LR production in this organism. In support of this hypothesis, sulfur limitation in batch cultures led to an approximate 1.5-fold decrease in the intracellular MC-LR quota (QMC) over the entire growth cycle, revealing a requirement for sulfur in MC production and suggesting that metabolic demand for methionine may limit MC synthesis. CrownKeywords: Bacteria (microorganisms); Cyanobacteria; Microcystis aeruginosa Amino acids; Batch culture; Chemostat culture; Cluster analysis; Cyanobacteria; Metabolism; Microcystin production; Microcystis aeruginosa; Sulfur201010.1016/j.hal.2009.08.0032016-02-24