Geosmin–producing Scytonema foetidum sp. nov. (Scytonemataceae, Cyanobacteria): morphology and molecular phylogeny

Abstract

A novel Scytonema species, Scytonema foetidum sp. nov. is described by combining morphological and genetic evidences. Two clonal strains of the new species were isolated from a wet soil sample taken from the Khek River in the lower northern part of Thailand. This species is morphologically similar to S. hofmanii, but can be differentiated by a small filament width, conically rounded apical cell, and sheath present throughout the whole trichome. The 16S ribosomal RNA (rRNA), rbcLX, and nifH phylogenetic trees indicated that S. foetidum clearly formed a unique cluster within the Scytonema sensu stricto clade and shared low 16S rRNA sequence similarity (<98.4%) with the phylogenetically related taxa, supporting separation at species level. The 16S–23S rRNA internal transcribed spacer (ITS) sequences of S. foetidum also possessed unique secondary structures in D1–D1′, Box B, and V3 helices, differentiating this species from other known Scytonema species. Furthermore, S. foetidum could produce the odoriferous compound, geosmin.