Unfortunately, few novel drugs have been developed specifically for MDR/PDR Gram-negative bacteria in recent years [8–10]. The development of new antimicrobial agents cannot keep up with the evolution of bacterial resistance. Thus, more efforts should be placed on discovering and developing new antimicrobial agents. As a source of new antibiotics, food-associated microorganisms have recently received increased attention. The well-known active compounds produced by these strains are peptide antibiotics, such as lantibiotics and lipopeptides [11–13]. Many of them are potentially useful in medical and food applications due to their low intestinal toxicity. To obtain antimicrobial
agents that are novel safe and
potent, a lot of food bacteria were isolated and screened for their antimicrobial activity. In this work, strain B7, a new bacterial isolate from a sample of dairy waste, was Navitoclax research buy found to produce antibiotics against both Gram-positive Selisistat and Gram-negative human pathogens. Based on the 16S rRNA gene sequence analysis as well as physiological and biochemical characterization, strain B7 was identified as Paenibacillus ehimensis. After isolation and purification of the fermentation products, the chemical structure and biological characteristics of the active compounds produced by P. ehimensis B7 were determined. Methods Strains and culture conditions Samples of dairy waste were collected from a local dairy industry in Wuxi. The
dairy waste samples were suspended in 0.1% sterile peptone water and antibiotic producing strains were isolated using a competitive inhibition method as previously described . Nutrition broth was used for routine culture. The active compounds were produced in synthetic Katznelson and Lochhead (KL) medium, which had the following composition (in g/L): glucose, 5; (NH4)2SO4, 1.5; MgSO4 .7H2O, 0.2; NaCl, 0.1; CaC12, 0.1; FeSO4 .7H2O, 0.01; ZnSO4, 0.01; MnSO4 .H2O, 0.0075; and KH2PO4 2.7. The medium was autoclaved and brought to a pH of 7.2. Staphylococcus epidermis CMCC 26069 was purchased from the National Center for Medical Culture Collections. S. aureus ATCC 43300, S. aureus ATCC 25923, E. coli ATCC 35218, and P. aeruginosa ATCC 27853 were purchased from the American Type Culture Collection Epothilone B (EPO906, Patupilone) (ATCC). Clinical isolates (P. aeruginosa 5215 and E. coli 5539) were isolated from patients at the Fourth People’s Hospital of Wuxi, Wuxi, China. The tested strains that were used to determine the sensitivity to the active compounds were routinely grown at 37°C on a nutrient agar or in a nutrient broth. For long-term storage, all of the strains were stored in 20% (v/v) glycerol at −80°C. This study was approved by the Ethics Committee of the Fourth People’s Hospital of Wuxi. Strain identification The morphology of strain B7 was examined by light microscopy after Gram-staining and spore staining.