The 51 clonal and non-axenic strains of Microcystis
(Table 1) were isolated by cultivation on solid medium
prepared by surface spreads containing cycloheximide
(50 mg l−1, Sigma–Aldrich, Dorset, UK). The strains
were grown at 21 ± 1 ◦C and 30 mmolm−2 s−1 (photometer
Li-cor 250), under a 14:10 h L:D (light:dark)
photoperiod in tubes containing 10 ml of modified liquid
BG-11 (Rippka et al., 1979) culture medium containing
nitrate (Bittencourt-Oliveira, 2000). The nine