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.