sp. nov., an Antibiotic-Siderophore Producing Novel Complex Species, Isolated from Malaysian Tropical Peat Swamp Soil.

A novel Gram negative rod-shaped bacterium, designated strain MSh1, was isolated from Southeast Pahang tropical peat swamp forest soil in Malaysia and characterized using a polyphasic taxonomy approach. The predominant cellular fatty acids (>10.0%) were C (31.7%), C cyclo (26.6%), and C cyclo ω8c (16.1%). The polar lipids detected were phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol. The predominant ubiquinone was Q-8. This revealed that strain MSh1 belongs to the genus . The type strain MSh1 can be differentiated from other complex (Bcc) species by phylogenetic analysis of 16S rRNA gene sequence, multilocus sequence analysis (MLSA), average nucleotide identity (ANI) and biochemical tests. DNA-DNA relatedness values between strain MSh1 and closely related type strains were below the 70% threshold value. Based on this polyphasic study of MSh1, it can be concluded that this strain represents a novel species within the Bcc, for which the name sp. nov. is proposed. The type strain is MSh1 (= DSM 100703 = MCCC 1K01245). The dichloromethane extract of MSh1 exhibited antimicrobial activity against four Gram positive bacteria ( ATCC 29212, ATCC 700802, ATCC 29213, ATCC 700699) and a Gram negative bacteria ( ATCC 25922). Further purification work has led to the isolation of Compound 1, pyochelin. Pyochelin demonstrated antimicrobial activity against four strains and three . strains with MIC-values of 3.13 μg/ml and 6.26 μg/ml, respectively. SEM analysis showed that the cellular morphology of ATCC 700802 was not affected by pyochelin; suggesting that it might target the intracellular components. Pyochelin, a siderophore with antimicrobial activity might be useful in treating bacterial infections caused by and , however further work has to be done.