Cylindrospermopsin (CYN）was hepatotoxic cyanotoxin identified in bloom-forming Cylindrospermopsis. To date, CYNs have been detected in Cylindrospermopsis, Raphidiopsis, Aphanizomenon, Anabaena , Oscillatoria, and Lyngbya. Cyanobacterial blooms occur perennially in numerous freshwater ecosystems, and CYN have been detected in some urban reservoirs of China. An overview of CYNs-producing species in total phytoplankton is essential for the risk assessment of CYNs. The Research Group led by Prof. LI Renhui at Institute of hydrobiology, Chinese Academy of Sciences made new progress in the diversity of CYN producers and their toxin biosynthesis genes. 

The researchers explored the phylogenetic distribution and evolution of cyr genes in cyanobacterial strains and water samples from China. Several Cylindrospermopsis and Raphidiopsis strains were confirmed to produce CYNs. Cloned cyr gene sequences from eight water bodies were clustered with cyr genes from Cylindrospermopsis and Raphidiopsis (C/R group) in the phylogenetic trees with high similarities (99%). Cyr sequences were observed to have different sequence insertions and repeats. Phylogenetic analysis of the C/R group revealed four conserved clades and a divergent Clade IV. Therefore, CYNs producers were sporadically distributed in congeneric and paraphyletic C/R group species in Chinese freshwater ecosystems. In the evolution of cyr genes, intragenomic translocations and intergenomic transfer between local Cylindrospermopsis and Raphidiopsis were emphasized and probably mediated by transposases. This research confirms the existence of CYN-producing Cylindrospermopsis in China and reveals the distinctive variations of cyr genes. 

This work was published in Applied and Environmental Microbiology with the title " Sporadic distribution and distinctive variations of cylindrospermopsin genes in cyanobacterial strains and environmental samples from Chinese freshwater bodies" September 2014 vol.80(17):5219-5230. 

CYN producers and biosynthesis gene cluster