Elaiomycins B and C, novel alkylhydrazides produced by Streptomyces sp. BK 190

Abstract

Dereplicated novel actinomycetes from neglected habitats provide high quality biological material for screening programs designed to detect novel bioactive secondary metabolites.2 Such organisms include neutrotolerant acidophilic streptomycetes which grow from pH 4.5 to 7.5, with an optimum between pH 5.0 and 5.5.3 Members of this group were isolated from a hay meadow soil taken from Cockle Park Experimental Farm in Northumberland, UK. The isolates were grown as submerged cultures in complex media, and extracts from the culture filtrates and mycelia included in our HPLC-diode array screening program to detect novel secondary metabolites by means of an in-house HPLC-UV-Vis database, which contains approximately 950 natural products, mainly antibiotics.4 Strain BK 190 was of interest because of the presence of three prominent peaks in the HPLC profile of a culture filtrate extract. The strain was assigned to the genus Streptomyces by its morphological and chemotaxonomic properties.5 Strain BK 190 formed an extensively branched substrate mycelium, a grey aerial spore mass and aerial hyphae, which differentiated into spiral chains of smooth-surfaced spores on oatmeal agar, contained LL-diaminopimelic acid, galactose, glucose and xylose as major sugars, N-acetylated muramic acid, predominant amounts of hexa- and octa-hydrogenated menaquinones with nine isoprene units, and produced iso- and anteiso-branched fatty acids with C15:0 and iso-C16:0 as major components. The temperature and pH ranges for growth were 10–35 °C and pH 4.0–8.0, respectively. Phylogenetic analyses showed that the organism was most closely related to the type strain of Streptomyces sanglieri; the two organisms shared a 16S rRNA similarity of 99.9%, a value that corresponds to a single nucleotide difference at 1434 locations.