Aliinostoc bakau sp. nov. (Cyanobacteria, Nostocaceae), a New Microcystin Producer from Mangroves in Malaysia

A new microcystin-producing mangrove cyanobacterium, Aliinostoc bakau sp. nov., was isolated from a tropical mangrove in Penang, Malaysia, and characterized using combined morphological and phylogenetic approaches. Cultures were established in liquid media of different salinities (0, 7, 14, 21, 28, and 35 ppt). Optimal growth observed at both 7 and 14 ppt was consistent with the origin of the strain from an estuarine mangrove environment. Phylogenetic analysis based on the 16S rRNA gene strongly indicated that the strain is a member of the genus Aliinostoc and is distinct from other currently sequenced species in the genus. The sequences and secondary structure of the 16S–23S ITS region D1–D1’ and Box–B helices provided further confirmation that the new species is clearly distinct from previously described Aliinostoc species. Amplification of the mcyE gene fragment associated with the production of microcystin in A. bakau revealed that it is identical to that in other known microcystin-producing cyanobacteria. Analysis of the extracts obtained from this strain by HPLC-MS/MS confirmed the presence of microcystin variants (MC-LR and -YR) at concentrations of 0.60 μg/L and MC-RR at a concentration of 0.30 μg/L. This is the first record of microcystin production from Aliinostoc species in tropical mangrove habitats.