Biodegradation of microcystin by a new Bacillus sp. isolated from a Saudi freshwater lake

Abstract

A new strain of Bacillus sp. was isolated from a Saudi eutrophic lake containing toxic cyanobacterial blooms. Based on phylogenetic analysis of the 16S rRNA gene sequence, the new strain most likely belonged to the genus Bacillus with a similarity of 81%. Using polymerase chain reaction (PCR), AMRI- 03 strain was shown to contain a gene homologues to mlrA that encodes the most important enzyme for microcystin degradation. The strain was capable of degrading microcystin-RR (MC-RR) (10 mgl^-1) in batch experiments under environmentally related conditions. The degradation of MC-RR was fully completed within 5 days after a lag period of 2 days. The MC-RR degradation by AMRI-03 strain occurred in a medium containing nitrogen and phosphorus, indicating that this could likely occur along with other organic compounds found in the environment. Therefore, the coexistence of such bacteria with MCs in the same environment can contribute to the self-purification of the ecosystem from such potent toxins.

Key words: Bacillus sp., 16S rRNA gene, degradation, microcystin, mlrA gene, polymerase chain reaction.