科研之友
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摘要
The cyanobacterial genus Chroococcus is well documented in freshwater habitats; however, less is known about the distribution, ecology and taxonomy of marine strains. In this study, we characterise six Chroococcus-like strains isolated from Tahiti, Hawaii, Cook Islands and New Zealand through sequencing of the 16S ribosomal RNA gene. We also assessed their toxin producing potential by screening for genes known to be involved in cyanotoxin production. The cell sizes (> 27x38 mu m) of all strains were notably larger than those described previously. Phylogenetic analysis of a partial (c. 700bp) region of the 16S rRNA gene showed that the six strains formed a single well-supported group (85% bootstrap support), despite their origins from several distantly separated Pacific locations. The strains were genetically most closely related to the recently proposed genus Limnococcus. The phylogeny also revealed the polyphyletic nature of the genus Chroococcus when using 16S rRNA sequence data, and we suggest further analysis is required. In a previous study, the Tahitian strain exhibited low toxicity to mice; however, none of four genes involved in cyanotoxin-production (mcyE, sxtA, cyrJ and anaC) that we tested for were detected. To increase knowledge on the ecology of marine Chroococcus-like strains, and to further delineate the taxonomic position of this group, a larger study using strains sourced from additional Pacific locations, as well as sites in the Indian and Atlantic Oceans, is recommended.
- 出版日期2017-3
