Genomic diversity and CRISPR‐Cas systems in the cyanobacterium Nostoc in the High Arctic

Abstract

Nostoc (Nostocales, Cyanobacteria) has a global distribution in the Polar Regions. However, the genomic diversity of Nostoc is little known and there are no genomes available for polar Nostoc. Here we carried out the first genomic analysis of the Nostoc commune morphotype with a recent sample from the High Arctic and a herbarium specimen collected during the British Arctic Expedition (1875-76). Comparisons of the polar genomes with 26 present-day non-polar members of the Nostocales family highlighted that there are pronounced genetic variations among Nostoc strains and species. Osmoprotection and other stress genes were found in all Nostoc strains, but the two Arctic strains had markedly higher numbers of biosynthetic gene clusters for uncharacterised non-ribosomal peptide synthetases, suggesting a high diversity of secondary metabolites. Since viral-host interactions contribute to microbial diversity, we analysed the CRISPR-Cas systems in the Arctic and two temperate Nostoc species. There were a large number of unique repeatspacer arrays in each genome, indicating diverse histories of viral attack. All Nostoc strains had a subtype I-D system, but the polar specimens also showed evidence of a subtype I-B system that has not been previously reported in cyanobacteria, suggesting diverse cyanobacteria-virus interactions in the Arctic.

Metagenome-Assembled Genome of Cyanocohniella sp. LLY from the Cyanosphere of Llayta, an Edible Andean Cyanobacterial Macrocolony

“…CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated) operons are defensive systems found in archaea and bacteria [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ] and were found in the Cyanocohniella sp. LLY genome.…”

Genomic Insights on the Functional Capabilities of the Cyano-Sphere of Edible Andean Nostoc Macrocolonies (Llayta)

“…According to Shao et al [43], the Cmr complex binding and cleaving of foreign RNA may involve a crRNA endoribonuclease activity coded at one of the Cmr1, Cmr3, Cmr4, or Cmr6 genes; in contrast, the Cmr2 gene is involved in binding specific targets. The crRNA transcribed by the CRISP array would bind to CAS proteins to recognize the foreign nucleic acid, which would be cleaved by Cas1 and Cas2 nucleases [44][45][46][47]. Sequences for CRISPR-CAS system operons found at the metagenome-assembled genome from Nostoc sp.…”

Population genomics and morphological data bridge the centuries of cyanobacterial taxonomy along the continuum of Microcoleus species

“… 33 In fact, the only historical herbarium-derived genomes of cyanobacteria were sequenced by Dvořák et al. 33 and Jungblut et al., 34 who obtained two genomes of Nostoc , and Stanojković et al., 6 who sequenced 8 herbarium specimens of Microcoleus up to two hundred years old (included in this paper). Microcoleus is an ideal cyanobacterium for obtaining herbarium genomes, due to its cosmopolitan distribution and ability to grow copious biomass.…”