Identification and characterization of novel surfactins produced by fungal antagonist Bacillus amyloliquefaciens 6B

Abstract

The broad-spectrum fungal antagonist, Bacillus amyloliquefaciens 6B (BA6B), isolated from the Jakhao coast of Kutch, India, was investigated for its antifungal metabolites using mass spectrometry. The cyclic lipopeptides harvested from the cell-free fermentation broth of BA6B by acid precipitation and subsequently dissolved in methanol were subjected to liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS/MS) for their identification and sequence determination. The 26 types of surfactin variants were identified from the methanolic extract by LC-ESI-MS/MS analysis. Among 26 surfactin species, several new cyclic as well as acyclic surfactin variants based on the variation in the β-hydroxy fatty acid (β-OH FA) chain length and/or in amino acid positions 4, 5, 6, and 7 were identified. The mass spectrometric analysis of crude extract also enabled the identification of 11 unique molecular mass ions with minimum two or maximum four types of isobaric peptide variants.

Lipid composition in a strain of Bacillus subtilis, a producer of iturin A lipopeptides that are active against uropathogenic bacteria

“…The highest signals were identified at m/z 1457, 1471, 1485, 1513 and 1527. A similar mass intensity was described in other studies that used MALDI MS/MS (Pathak et al 2014; Yang et al 2015). …”

Detection of biosurfactants inBacillusspecies: genes and products identification

“…Using the IDA method, molecules with molecular mass ions in the range of m/z 1051-1093 were detected and assigned as iturins ( Fig. 5b) (Pathak et al 2014). In the range 3Á0-3Á5 min, peaks of fengycin LPs were observed (Fig.…”

“…The same retention time was observed for the applied surfactin standard. 5b) (Pathak et al 2014). However, in each sample two surfactin homologues (C14 and C15) strongly dominated comprising together from 75 to even 91% of the whole estimated surfactin content.…”

Antibacterial activity againstRalstonia solanacearumof the lipopeptides secreted from theBacillus amyloliquefaciensstrainFJAT‐2349

“…Four main isoforms of fengycin including fengycin A, fengycin B, fengycin A 2 and fengycin B 2 were observed in the LPs secreted from strain FJAT-2349, which were identified according to the four key diagnostic product ions 1080/966, 1108/994, 1066/952 and 1094/980 (Pathak et al 2014). Thus, the precursor ions at m/z 1436Á1 and 1464Á1 with fragmentation ions at m/z 1080 and 966 (corresponding to the sodium adducts of production ions at m/z 1102 and 988) were identified as C 14 fengycin A and C 16 fengycin A respectively; the protonated molecules at m/z 1450Á1 (R t 27Á0 and 27Á8 min), and m/z 1478Á2 (R t 32Á1 min) possessing two key product ions at m/z 1094 and 980 (corresponding to the sodium adducts of production ions at m/z 1116 and 1002) were identified as C 14 fengycin B 2 and C 16 fengycin B 2 respectively; the peaks at m/z 1450Á1 (R t 29Á0 and 29Á5 min) with product ions of 1066 and 952 (corresponding to the sodium adducts of production ions at m/z 1088 and 974) were identified as C 16 fengycin A 2 ; the precursor ions at m/z 1492Á2 (R t 32Á8 and 33Á5 min) and m/z 1506Á2 (35Á5 min) yielded two significant protonated ions at m/z 1108 and 994 (corresponding to the sodium adducts of the production ions at m/z 1130 and 1016), which were identified as C 16 fengycin B and C 17 fengycin B respectively.…”