Unexpected Genetic Diversity of Nostocales (Cyanobacteria) Isolated from the Laurel Forest Phyllosphere in the Canary Islands (Spain)

Le résumé fourni par la source

A total of 96 strains of Nostocales (Cyanobacteria) were established from the laurel forest phyllosphere in the Canary Islands (Spain) and Azores (Portugal) using enrichment media lacking combined nitrogen. The strains were characterized by light microscopy and SSU rRNA gene comparisons. Morphologically, most strains belonged to two different morphotypes, termed “Nostoc-type” and “Tolypothrix-type”. Molecular phylogenetic analysis of 527 SSU rRNA gene sequences of cyanobacteria (95 sequences established during this study plus 392 sequences from Nostocales and 40 sequences from non-heterocyte-forming cyanobacteria retrieved from the databases) revealed that none of the SSU rRNA gene sequences from the laurel forest phyllosphere was identical to a database sequence. In addition, the genetic diversity of the isolated strains was high with 42 different genotypes (44% of the sequences), recognized. Among the new genotypes were also terrestrial members of genus Nodularia as well as members of genus Brasilonema. It is concluded that heterocyte-forming cyanobacteria represent a still largely undersampled component of the phyllosphere in subtropical/tropical forests.

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