title: Characterization of two antimicrobial peptides produced by a halotolerant Bacillus subtilis strain SK.DU.4 isolated from a rhizosphere soil sample.
abstract: A bacterial strain producing two antimicrobial peptides was isolated from a rhizosphere soil sample and identified as Bacillus subtilis based on both phenotypic and 16S rRNA gene sequence phylogenetic analysis. It grew optimally up to 14% NaCl and produced antimicrobial peptide within 24 h of growth. The peptides were purified using a combination of chemical extraction and chromatographic techniques. The MALDI-TOF analysis of HPLC purified fractions revealed that the strain SK.DU.4 secreted a bacteriocin-like peptide with molecular mass of 5323.9 Da and a surface-active lipopeptide (m/z 1056 Da). The peptide mass fingerprinting of low-molecular-weight bacteriocin exhibited significant similarity with stretches of secreted lipoprotein of Methylomicrobium album BG8 and displayed 70% sequence coverage. MALDI MS/MS analysis elucidated the lipopeptide as a cyclic lipopeptide with a β-hydroxy fatty acid linked to Ser of a peptide with seven α-amino acids (Asp-Tyr-Asn-Gln-Pro-Asn-Ser) and assigned it to iturin-like group of antimicrobial biosurfactants. However, it differed in amino acid composition with other members of the iturin family. Both peptides were active against Gram-positive bacteria, suggesting that they had an additive effect.
authors.affiliation: MTCC and Gene Bank, CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh, 160036, India. suresh@imtech.res.in.
authors.forename: Piyush
authors.initials: P
authors.lastname: Baindara
authors.forename: Santi M
authors.initials: SM
authors.lastname: Mandal
authors.forename: Niharika
authors.initials: N
authors.lastname: Chawla
authors.forename: Pradip Kumar
authors.initials: PK
authors.lastname: Singh
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Pinnaka
authors.forename: Suresh
authors.initials: S
authors.lastname: Korpole