Taxonomy and biological activities of a novel Saccharothrix species from soil of Sichang Island

Abstract

Actinobacteria are the sources of bioactive natural products. Rare actinobacteria are the less frequently isolated genera of actinobacteria. During an investigation of diversity of rare actinobacteria, actinobacteria isolate SC076T was isolated from a soil sample collected from Sichang Island, Chonburi Province, Thailand. The strain showed the highest 16S rRNA gene similarity to Saccharothrix australiensis DSM 43800T (98.58%) and Saccharothrix espanaensis DSM 44229T (98.58%). The zigzag morphology of the spore chain was observed on the aerial mycelia. meso-diaminopimelic acid was detected in the peptidoglycan. Whole-cell sugars contained rhamnose, ribose, mannose glucose and galactose. Polar lipids are phosphatidylethanolamine, hydroxyphosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol mannoside, phosphatidyl inositol, unidentified ninhydrin positive glycolipid, unidentified glycolipid and four unidentified lipids. Menaquinones are MK-9(H4), MK-9(H8), MK-9(H2) and MK-9(H0). The predominant cellular fatty acids were iso-C16:0, iso-C15:0, and anteiso-C17:0. The strain showed both dDNA-DNA hybridization value and average nucleotide identity of 77.7 – 82.5% and 84.9 – 86.7%, respectively. Moreover, the strain showed antimicrobial activity against gram positive pathogenic organisms but did not produce any antifungal activity. For the anticancer activity screening, MTT assay showed IC50 value 126.668 µg/mL against non-small lung cancer H460 cells. In the higher dose strain showed cytotoxic effect. Unfortunately, the strain did not have potential cell migration and cell invasion effects. Besides, antioxidant and anticholinease activity also tested but no activity represented from the strain. However, from the secondary metabolite profiling from the whole genome sequences it showed 100% similarity with Terpene, PKS compound. Besides chemical profiling of the crude extract determines the strain contains some antibiotic potential chemical compound that will be isolated and purified as further study. Based on the taxonomic evidence, strain SC076T represents a novel species of the genus Saccharothrix for which the name Saccharothrix oblica sp. nov. is proposed. Type strain is SC076T (=TBRC 14540T =NBRC 115117T). In conclusion, these finding ensured that strain SC076T is the novel species of genus Saccharothrix and possesses antibacterial activity as well as cytotoxic effects. The Actinobacteria isolated from soil sample provided biological activity information in drug discovery as the good candidates for the development of antibiotics.