An Effective Strategy for Identification of Highly Unstable Bacillaenes

Abstract

Exploration of unstable compounds is a rarely explored area of natural product research. We describe the integration of genomic and metabolomic analyses with bioassay-guided compound mining to effectively explore unstable bacillaenes. New bacillaene structures (2, 4, and 5) were identified from compound mixtures using the DANS-SVI (differential analysis of 2D NMR spectrum−single spectrum with variable intensities) method, which were further verified by the isolation of the pure compounds under strictly controlled conditions. Compound 1 exhibited antibacterial activity against multi-drug-resistant bacterial strains, while glycosylation decreased the activity of the bacillaene scaffold.

Bacillaenes: Decomposition Trigger Point and Biofilm Enhancement in Bacillus

“…Decomposition of the non-gBAEs was more easily triggered compared to the glycosylated analogues. This result revealed that the glycosylation stabilizes the bacillaene scaffold, which supports our previous suggestion …”

“…The molecular formulas of 1–3 were established as C 34 H 48 N 2 O 6 , C 40 H 58 N 2 O 11 , and C 40 H 60 N 2 O 11 , respectively, on the basis of the HR-ESIMS data ([M + H] + at m / z 581.3595, 743.4163, and 745.4280). Compounds 1 and 3 were confirmed to be bacillaene A and 14′,15′-dihydro-bacillaene B, respectively, as reported in our earlier work, and 2 was identified as bacillaene B by 1D and 2D NMR data assignments (Figure S7 and Table S1). Compounds 1 and 2 , being quantified by the standard curves, underwent time- (0–48 h) and dose-dependent (0.1–10 μg/mL) stability tests at normal bioassay conditions (aqueous solution system, 37 °C, in the dark) using UPLC-MS. As shown in Figure S8, bacillaene A ( 1 ) was rather unstable in aqueous solution.…”

“…virulence, colonization, motility, stress response, and/or biofilm formation) in nature at their subinhibitory concentrations (SICs) . Interestingly, we observed that both of bacillaene A ( 1 ) and bacillaene B ( 2 ) accelerated self-biofilm formation in the B-9987 strain at low concentrations of 1.0 and 0.1 μg/mL (Figure ), which were far below than their antibiotic MICs (>10 μg/mL). , Then, to further evaluate the effects of bacillaenes on the self-biofilm formation in the B-9987 strain at higher concentrations, we used Fr. BAEs/Fr.…”

“…In our recent study on bacillaenes, we identified a series of new glycosylated bacillaenes (gBAEs) (14′,15′-dihydro-bacillaene B, 12′,13′- trans -14′,15′-dihydro-bacillaene B, and bacillaene C) using a combined strategy of genome, 2D-NMR metabolome coupled with bioassay, and illustrated that glycosylation generally decreases the antibacterial activity . Herein, as continuing studies, the stability and biological function of bacillaenes were investigated.…”

Antimicrobial Activities of Lipopeptides and Polyketides of Bacillus velezensis for Agricultural Applications

“…Despite antibacterial activity of this antibiotic against multi-drug-resistant bacterial isolates, for many years, characterization of bacillaene using the traditional methods based on fractionations was proved challenging, owing to its chemical instability [11]. On exposure to light or room temperature, bacillaene decomposes rapidly, which hindered earlier attempts to identify the biosynthetic pathway of this antibiotic molecule [79]. Antibacterial polyketide bacillaene synthesized by B. velezensis FZB42, exhibited a minor extent of bacteriostatic effect against Erwinia amylovora, a causal agent of fire blight disease [32].…”