Identification of four novel Streptomyces isolated from machair grassland soil using a culture-based bioprospecting strategy: Streptomyces caledonius sp. nov., Streptomyces machairae sp. nov., Streptomyces pratisoli sp. nov. and Streptomyces achmelvi

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, in which carbonate minerals dominate. Representatives were shown to be bioactive in primary and secondary antimicrobial screens conducted through standard plug assays. The comparison of the whole-genome sequences showed that four of the isolates were novel species in the genus <i>Streptomyces</i>, for which the names <i>Streptomyces caledonius</i> sp. nov. (=DSM 118365; =NCIMB 15554), <i>Streptomyces machairae</i> sp. nov. (=DSM 118363; =NCIMB 15553), <i>Streptomyces pratisoli</i> sp. nov. (=DSM 118364; =NCIMB 15555) and <i>Streptomyces achmelvichensis</i> sp. nov. (=NCIMB 15556; =DSM 118366) are proposed. Genomes of the novel strains were found to be rich in biosynthetic gene clusters predicted to encode for diverse, specialized metabolites, notably antibiotics. They also contained stress-related genes that provided an insight into how streptomycetes cope with the prevailing conditions in machair grassland soils. It can be concluded that selective isolation and dereplication of streptomycetes from the unique machair habitat provides a practical way of isolating novel <i>Streptomyces</i> strains for ecological and biotechnological studies.