Table 2 Effect of divalent cations on antibacterial activity of lipopeptide antibiotics (PE1 and PE2) produced by Paenibacillus ehimensis B7 Antibiotic MIC (μg/mL)   P. aeruginosa ATCC 27853 S. aureus ATCC 43300 PE1 8 4 PE1 + 10 mM CaCl2 >64 8 PE1 + 10 mM MgCl2 >64 8 Cytotoxicity The cytotoxicity of the purified compounds (PE1 and PE2) against mammalian cells was tested by the CCK-8 assay. PE1 and PE2 showed little cytotoxicity

against HEK293T cells (treatment time, 24 h) at all of concentrations that were tested (1 μg/mL to 128 μg/mL) (Figure 5). Figure 5 Cytotoxicity of PE1 and PE2 to mammalian cells. Cytotoxicity of PE1 and PE2 to HEK293T was measured with the CCK-8 assay. The concentrations of PE1 and PE2 ranged from 0 to 128 μg/mL. The positive control was 0.1% Triton X-100. Discussion In the present study, B7, a new bacterial strain with see more CP-868596 nmr potent antimicrobial activity was isolated from a dairy waste sample, and identified as P. ehimensis. Phylogenetic analysis based on 16S rRNA gene indicated that the isolate was closely related to P. elgii, P. koreensis, and P. tianmuensis

(data not shown). This group of bacteria produces diverse antimicrobial agents, including lipopeptides [15, 22, 23], lantibiotics [24] and macrolide [14]. Interestingly, most extensively described lipopeptide antibiotics from this group of bacteria contain a high percentage of both Dab and a C6-C7 N-terminal fatty acyl chain [15, 22]. The active compounds (PE1 Megestrol Acetate and PE2) that are produced by P. ehimensis B7 were structurally similar to the lipopeptide polypeptins (A and B) that were previously isolated from Bacillus circulum[25]. Polypeptin is a group of polypeptide antibiotics composed of a cyclic nonapeptide moiety and a fatty acid side chain. To date, five polypeptin-type antibiotics, including polypeptin A, polypeptin B, permetin A, BMY-28160, and pelgipeptin D, have been extensively described [25–28]. Polypeptins A and B, which have the same molecular selleck products formula, have identical amino acid moieties but vary in

the structure of fatty acids. BMY-28160 and permetin A only differ from each other at position 2 in peptide moieties (i.e., L-Val is in BMY-28160, and L-Ile in permetin A). Pelgipeptin D and permetin A only differ from each other in the fatty acid moiety, while permetin A differs from polypeptin A only in the amino acid at position 9 (i.e., L-Ser is present in permetin A, and L-Thr in polypeptin A). Polypeptin-type antibiotics were known to have a broad spectrum of antimicrobial activity against many Gram-positive and Gram-negative bacteria [25]. The molecular mass of PE1 was identical to that of polypeptin A and B, and the amino acid sequences and antimicrobial spectra were extremely similar, suggesting PE1 and polypeptin (A or B) are most likely the same compound.