A new Streptomyces strain isolated from Saharan soil produces di-(2-ethylhexyl) phthalate, a metabolite active against methicillin-resistant Staphylococcus aureus

An actinomycete strain designated G60 was isolated from a Saharan soil sample in Ghardaïa, Algeria, by a dilution agar plating method using chitin-vitamin agar medium supplemented with penicillin. Morphological and chemical studies indicated that this strain belonged to the genus Streptomyces . Analysis of the 16S rDNA sequence showed an identity level within Streptomyces species, with S. coerulescens ISP 5146 T and S. bellus ISP 5185 T the most closely related (100 % for each). However, the comparison of the morphological and physiological characteristics of the strain with those of the two nearest species showed significant differences. Strain G60 had a very strong activity against pathogenic staphylococci, including methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, other clinical isolates of MRSA and vancomycin resistant S. aureus (VRSA) S1. One antimicrobial compound was extracted by n -hexane from the ISP2 culture medium at 5 days of fermentation culture and purified by HPLC. The chemical structure of the compound was determined after spectroscopic ( 1 H NMR, 13 C NMR, 1 H- 1 H COSY and 1 H- 13 C HMBC spectra), and spectrometric (mass spectrum) analyses. The bioactive compound was identified as di-(2-ethylhexyl) phthalate.