Abstract
Toxic metabolites are produced by many cyanobacterial species. There are limited data on toxigenic benthic, mat-forming cyanobacteria, and information on toxic cyanobacteria from Central Asia is even more scarce. In the present study, we examined cyanobacterial diversity and community structure, the presence of genes involved in toxin production and the occurrence of cyanotoxins in cyanobacterial mats from small water bodies in a cold high-mountain desert of Eastern Pamir. Diversity was explored using amplicon-based sequencing targeting the V3-V4 region of the 16S rRNA gene, toxin potential using PCR-based methods (mcy, nda, ana, sxt), and toxins by enzyme-linked immunosorbent assays (ELISAs) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular identification of cyanobacteria showed a high similarity of abundant taxa to Nostoc PCC-73102, Nostoc PCC-7524, Nodularia PCC-935 and Leptolyngbya CYN68. The PCRs revealed the presence of mcyE and/or ndaF genes in 11 samples and mcyD in six. The partial sequences of the mcyE gene showed high sequence similarity to Nostoc, Planktothrix and uncultured cyanobacteria. LC-MS/MS analysis identified six microcystin congeners in two samples and unknown peptides in one. These results suggest that, in this extreme environment, cyanobacteria do not commonly produce microcystins, anatoxins and cylindrospermopsins, despite the high diversity and widespread occurrence of potentially toxic taxa.
Highlights
Microbial mats are multi-structural communities comprised of eukaryotic algae, fungi, bacteria, including cyanobacteria and archaea, which form complex biofilms [1,2]
Microbial mat samples were analyzed for LC-MS/MS as well as screened for known toxin-encoding genes
In this study we report limited toxin-production by cyanobacteria in microbial mat communities from a cold high-mountain desert (Eastern Pamir, Tajikistan)
Summary
Microbial mats are multi-structural communities comprised of eukaryotic algae, fungi, bacteria, including cyanobacteria and archaea, which form complex biofilms [1,2]. Cyanobacteria play a significant role in these microbial mat communities due to their ability to conduct photosynthesis, fix atmospheric nitrogen and produce extracellular polysaccharides. They provide organic carbon and biologically active nitrogen, and help to maintain the shape and structure of the microbial mats. Production of scytonemin and mycosporine-like amino acids by cyanobacteria help to protect them from UV radiation [5,6] They produce many other bioactive compounds [7], which are believed to increase their chances of surviving in inhospitable environments, such as extremely cold or hot deserts and hypersaline habitats [3,4,8]
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