Iron uptake by microcystin-producing and non-microcystin-producing strains of Microcystis aeruginosa was investigated through short-term uptake assays. Although strain-specific differences were observed, the siderophore-independent Fe uptake kinetics were essentially similar (e.g., maximum uptake rates of 2.0 to 3.3 amol·cell(-1)·h(-1)) for the wild-type toxic strain PCC7806 and a genetically engineered mutant unable to produce microcystin.