Identification of novel Streptomyces isolated from machair grassland soil using a culture-based bioprospecting strategy.

A culture-dependent bioprospecting strategy, based on the use of several selective isolation media, revealed the presence of relatively high numbers of streptomycete-like colonies from machair grassland soil. Representative colonies taken from the isolation plates were assigned to five multi-membered and two single-membered colour-groups, distinguished by their ability to form pigments on oatmeal and peptone-yeast extract-iron agar. Colour-group representatives were shown to be bioactive in primary and secondary antimicrobial screens conducted through standard plug assays. Corresponding whole-genome sequencing, using a MinION flow cell and a Native Barcoding kit from Oxford Nanopore Technologies, showed that the isolates had genome sizes ranging from 8.1 to 9.8Mbp. Comparison of the whole-genome sequences with those of the most closely related validly published Streptomyces species showed that four of the isolates were novel species in the genus Streptomyces.