Streptomyces globosus DK15 and Streptomyces ederensis ST13 as new producers of factumycin and tetrangomycin antibiotics

Abstract

Fifty seven soil-borne actinomycete strains were assessed for the antibiotic production. Two of the most active isolates, designed as Streptomyces ST-13 and DK-15 exhibited a broad range of antimicrobial activity and therefore they were selected for HPLC fractionation against the most suppressed bacteria Staphylococcus aureus (ST-13) and Chromobacterium violaceum (DK-15). LC/MS analysis of extracts showed the presence of polyketides factumycin (DK15) and tetrangomycin (ST13). The taxonomic position of the antibiotic-producing actinomycetes was determined using a polyphasic approach. Phenotypic characterization and 16S rRNA gene sequence analysis of the isolates matched those described for members of the genus Streptomyces. DK-15 strain exhibited the highest 16S rRNA gene sequence similarity to Streptomyces globosus DSM-40815 (T) and Streptomyces toxytricini DSM-40178 (T) and ST-13 strain to Streptomyces ederensis DSM-40741 (T) and Streptomyces phaeochromogenes DSM-40073 (T). For the proper identification, MALDI-TOF/MS profile of whole-cell proteins led to the identification of S. globosus DK-15 (accession number: KX527570) and S. ederensis ST13 (accession number: KX527568). To our knowledge, there is no report about the production of these antibiotics by S.globosus and S. ederensis, thus isolates DK15 and ST13 identified as S. globosus DK-15 and S.ederensis ST-13 can be considered as new sources of these unique antibacterial metabolites.

Keywords: 16S rRNA; Factumycin; MALDI-TOF MS; Streptomyces; Tetrangomycin.

Figure 1

Fractionation RP-HPLC chromatogram of tetrangomycin, UV spectrum of tetrangomycin with the max at 268 nm, and ESI-HRMS spectrum, showing the prominent ion clusters for [M+H]+ at m/z 339.0861.

Figure 2

Fractionation RP-HPLC chromatogram of factumycin, UV spectrum of factumycin with the max. at 364 nm, and ESI-HRMS spectrum, showing the prominent ion clusters for [M+H]+ at m/z 743.4268.

Figure 3

Comparison between 16S rRNA phylogenetic tree and the MSP dendrogram. A. Mean spectra projection (MSP) dendrogram, B. 16S rRNA based phylogenetic tree of Streptomyces type strains, T1-T11 – DSM type cultures used for grouping of Streptomyces species, T1 - Streptomyces viridis DSM-42078 (T), T2 - S. phaeochromogenes DSM- 40788 (T), T3 - S. ederensis DSM-40741 (T), T4 - S. iakyrus DSM-40482 (T), T5 - S. griseochromogenes DSM-40499 (T), T6 - S. gougerotii DSM-40324 (T), T7 - S. albus DSM-40313 (T), T8 - S. diastaticus DSM-40495 (T), T9 - S. alboflavus DSM-40045 (T), T10 - S. toxytricini DSM-40178 (T), T11 - S. globosus DSM-41122 (T).