Desmonostoc cockrellii sp. nov. (Nostocales, Cyanobacteria): a new record of a subaerophytic species from The Habitat Penang Hill, Malaysia

Subaerophytic cyanobacterial diversity is poorly known in Malaysian rainforests generally and at Penang Hill specifically. A new subaerophytic species of cyanobacteria, Desmonostoc cockrellii sp. nov., was isolated from rocky surfaces along trails in The Habitat Penang Hill, Malaysia. Polyphasic analysis identified unique morphological structures such as larger dimensions of akinetes and bubble formations within colonies grown on agarized medium. Toxin–encoding genes for microcystin, nodularin, cylindrospermopsin, anatoxin– a and saxitoxin were not detected. The 16S rRNA gene phylogeny inferred by both maximum likelihood and Bayesian inference placed our four isolates within the Desmonostoc clade, distinct from previously characterised Desmonostoc species. The length and nucleotide sequences of the secondary structures of Box–B and V2 helices further differentiated them from known members of the genus. Fatty acid profiling showed that saturated fatty acids (53.7–77.5% dwt.) dominated over monosaturated fatty acids (8.6–22% dwt.) and polyunsaturated fatty acids (13.9–24.3% dwt.). The most abundant fatty acids were butyric acid (4:0), palmitic acid (16:0), oleic acid (18:1), γ–linolenic acid (18:3) and docosahexaenoic acid (22:6). Clear differences were apparent between the different isolates of D. cockrellii sp. nov. in the presence or absence and percentage composition of these fatty acids.