Unicellular Microcystis aeruginosa cannot revert back to colonial form after short-term exposure to natural conditions

Colonial Microcystis aeruginosa isolates tend to lose their typical colonial morph after some generations under laboratory conditions, one interesting but yet important question is whether unicellular M. aeruginosa, originally isolated from the field, can revert back to colonial morphology when growing back in natural waters. Based on this idea, we employed dialysis bags and plastic bottles to conduct an in situ experiment. Each of the dialysis bags and plastic bottles was filled with unicellular M. aeruginosa with high concentrations and then submerged to two natural lakes (lake Caiyue and Lake Taihu) for 40 and 28 days, respectively. Results showed M. aeruginosa grew well in dialysis bags but not in plastic bottles; no colonies were observed in M. aeruginosa incubated in either dialysis bags or plastic bottles exposed in both lakes. This suggests laboratory maintained unicellular M. aeruginosa cannot revert back to colonial form after short-term exposure in natural conditions. (C) 2013 Elsevier Ltd. All rights reserved.