Sporadic Distribution and Distinctive Variations of Cylindrospermopsin Genes in Cyanobacterial Strains and Environmental Samples from Chinese Freshwater Bodies

Abstract

e Increasing reports of cylindrospermopsins (CYNs) in freshwater ecosystems have promoted the demand for identifying all of the potential CYN-producing cyanobacterial species. The present study explored the phylogenetic distribution and evolution of cyr genes in cyanobacterial strains and water samples from China. Four Cylindrospermopsis strains and two Raphidiopsis strains were confirmed to produce CYNs. Mutant cyrI and cyrK genes were observed in these strains. 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%). Four cyrI sequence types and three cyrJ sequence types were observed to have different sequence insertions and repeats. Phylogenetic analysis of the rpoC1 sequences of the C/R group revealed four conserved clades, namely, clade I, clade II, clade III, and clade V. High sequence similarities (>97%) in each clade and a divergent clade IV were observed. Therefore, CYN 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.

Community Structures of Phytoplankton with Emphasis on Toxic Cyanobacteria in an Ohio Inland Lake during Bloom Season

“…The findings of the saxitoxin ( sxt ) gene in Harsha Lake samples indicated the potential production of this neurotoxin of A. circinalis and Aphanizomenon sp. As for Cylindrospermopsis , the sequences observed in this study were similar to the isolate sequences from Chinese waters like Xihu Lake, Qiandun Lake and Qingdao pond, which mostly revealed no presence of toxic genes ( cyrA and cyrL ) [19]. However, rpoC based genotypes might not necessarily indicate whether Cylindrospermopsis showed cyr gene positive, considering rpoC gene presented in both toxic and nontoxic species, while the cyr gene was found to sporadically distribute in cyanobacterial strains and environmental samples [19].…”

“…As for Cylindrospermopsis , the sequences observed in this study were similar to the isolate sequences from Chinese waters like Xihu Lake, Qiandun Lake and Qingdao pond, which mostly revealed no presence of toxic genes ( cyrA and cyrL ) [19]. However, rpoC based genotypes might not necessarily indicate whether Cylindrospermopsis showed cyr gene positive, considering rpoC gene presented in both toxic and nontoxic species, while the cyr gene was found to sporadically distribute in cyanobacterial strains and environmental samples [19]. Currently HAB monitoring using microscopy for phytoplankton and analytical analysis for cyanotoxin is recommended by local agencies such as OH EPA in their State of Ohio Harmful Algal Bloom Response Strategy For Recreational Waters [7].…”

“…Phylogenetic analysis on rpoC sequences (n = 47 sequences from 8 libraries) showed most (64%) to be 98% - 100% similar to C. raciborskii . All the sequences (93% similarity) could be grouped into two clades (Figure 8) with similarity to isolated sequences from various water of China, such as Xihu Lake, Qiandun Lake and Qingdao pond [19]. …”

Toxic potencies of metabolite(s) of non-cylindrospermopsin producing Cylindrospermopsis raciborskii isolated from temperate zone in human white cells

“…The toxin profile of C. raciborskii appears to be diversified in relation to the geographical zone . In general, CYN-producing strains occur in Australia and Asia (Jiang et al, 2014), whereas strains capable of saxitoxins (neurotoxic alkaloids) production are found in South America (Hoff-Risseti et al, 2013). African and European strains have not been shown to produce any known cyanotoxin (Haande et al, 2008; although the crude extracts of the latter were demonstrated to exhibit potentially toxic properties (Antal et al, 2011).…”

Advances in genomics, transcriptomics and proteomics of toxin‐producing cyanobacteria

“…The Chinese cylindrospermopsin‐producing strains were shown to retain the cyrN and cyrO genes within the aforementioned hyp locus, whereas strains lacking the cyr gene cluster contained the cyrO gene at this position. Taken together this suggests that cyrO was present prior to the initial acquisition of the cluster (Jiang et al ., ) and that cyrN within this region can be viewed as a marker of strains that have acquired the cluster at some point and have subsequently lost or translocated the operon. The varying arrangement of the cyr gene cluster, and the replacement with the saxitoxin ( sxt ) gene cluster within geographically distant strains of the Cylindrospermopsis/Raphidiopsis complex, raises a number of questions regarding the timing of these recombination events.…”