BackgroundThe prevalence of drug-resistant bacteria has encouraged the search for novel antimicrobial compounds. Food-associated microorganisms, as a source of new antibiotics, have recently received considerable attention. The objective of this study was to find novel antimicrobial agents produced by food microorganisms.ResultsA bacterial strain B7, which has potent antimicrobial activity, was isolated from a sample of dairy waste. This strain was identified as Paenibacillus ehimensis based on the 16S rRNA gene sequence analysis, physiological and biochemical characterization. Two active compounds (PE1 and PE2) were obtained from P. ehimensis B7. Mass spectrometry (MS) analysis showed that the molecular masses of PE1 and PE2 were 1,114 and 1,100 Da, respectively. The tandem MS and amino acid analysis indicated that PE1 and PE2 were analogs of polypeptin, and PE2 was characterized as a new member of this family. Both compounds were active against all tested bacterial pathogens, including methicillin resistant Staphylococcus aureus, Escherichia coli, and pan-drug resistant Pseudomonas aeruginosa clinical isolate. Time-kill assays demonstrated that at 4 × MIC (minimum inhibitory concentration), PE1 and PE2 rapidly reduced the number of viable cells by at least 3-orders of magnitude, indicating that they were bactericidal antibiotics.ConclusionsIn the present work, two cationic lipopeptide antibiotics (PE1 and PE2) were isolated from P. ehimensis B7 and characterized. These two peptides showed broad antimicrobial activity against all tested human pathogens and are worthy of further study.

Some endophyte bacteria can improve plant growth and suppress plant diseases. However, little is known about the potential of endophytes bacteria to promote wheat growth and suppress the Fusarium seedling blight pathogen Fusarium graminearum. This study was conducted to isolate and identify endophytic bacteria and evaluate their efficacy for the plant growth promotion and disease suppression of Fusarium seedling blight (FSB) in wheat. The Pseudomonas poae strain CO showed strong antifungal activity in vitro and under greenhouse conditions against F. graminearum strain PH-1. The cell-free supernatants (CFSs) of P. poae strain CO were able to inhibit the mycelium growth, the number of colonies forming, spore germination, germ tube length, and the mycotoxin production of FSB with an inhibition rate of 87.00, 62.25, 51.33, 69.29, and 71.08%, respectively, with the highest concentration of CFSs. The results indicated that P. poae exhibited multifarious antifungal properties, such as the production of hydrolytic enzymes, siderophores, and lipopeptides. In addition, compared to untreated seeds, wheat plants treated with the strain showed significant growth rates, where root and shoot length increased by about 33% and the weight of fresh roots, fresh shoots, dry roots, and dry shoots by 50%. In addition, the strain produced high levels of indole-3-acetic acid, phosphate solubilization, and nitrogen fixation. Finally, the strain demonstrated strong antagonistic properties as well as a variety of plant growth-promoting properties. Thus, this result suggest that this strain could be used as an alternate to synthetic chemicals, which can serve as an effective method of protecting wheat from fungal infection.