Bacteria and fungi are major phytopathogens which substantially affect global agricultural productivity. In the present study, Streptomyces sp. AN090126, isolated from agricultural suppressive soil in Korea, showed broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In the 96-well plate assay, the fermentation filtrate of Streptomyces sp. AN090126 exhibited antimicrobial activity, with a minimum inhibitory concentration (MIC) of 0.63–10% for bacteria and 0.63–3.3% for fungi. The MIC of the partially purified fraction was 20.82–250 µg/mL for bacteria and 15.6–83.33 µg/mL for fungi. Gas chromatography–mass spectrometry (GC-MS) analysis revealed that AN090126 produced various volatile organic compounds (VOCs), including dimethyl sulfide and trimethyl sulfide, which inhibited the growth of pathogenic bacteria and fungi in in vitro VOC assays. In pot experiments, the fermentation broth of Streptomyces sp. AN090126 reduced tomato bacterial wilt caused by Ralstonia solanacearum, red pepper leaf spot caused by Xanthomonas euvesicatoria, and creeping bentgrass dollar spot caused by Sclerotinia homoeocarpa in a dose-dependent manner. Moreover, the secondary metabolites derived from this strain showed a synergistic effect with streptomycin sulfate against streptomycin-resistant Pectobacterium carotovorum subsp. carotovorum, the causative agent of Kimchi cabbage soft rot, in both in vitro and in vivo experiments. Therefore, Streptomyces sp. AN090126 is a potential biocontrol agent in controlling plant diseases caused by pathogenic bacteria and fungi, specifically by the streptomycin-resistant strains.

The over and repeated use of chemical bactericides to control plant bacterial diseases has resulted in unwanted effects, such as environmental pollution, residual toxicity, and resistance buildup in bacterial pathogens. Many previous studies have aimed to develop biological control agents to replace chemical bactericides. In this study, the antibacterial efficacy of the fermentation broth of Paenibacillus elgii JCK-5075 and its antibacterial compounds were evaluated against plant pathogenic bacteria, using both in vitro and in vivo bioassays. Pelgipeptins (PGPs) A, B, C, and D that were isolated from P. elgii JCK-5075 displayed broad-spectrum antibacterial activity against various plant pathogenic bacteria. The fermentation broth of P. elgii JCK-5075, at 5-fold dilution, effectively suppressed the development of tomato bacterial wilt, Kimchi cabbage soft rot, and red pepper bacterial leaf spot in pot experiments with control values of 81, 84, and 67%, respectively. PGP-A and C, at 200 μg/ml, were also found to markedly reduce the development of Kimchi cabbage bacterial soft rot by 75% and tomato bacterial wilt by 83%, respectively, and their disease control efficacy was comparable to that of oxolinic acid with control values of 81 and 85%, respectively. Additionally, the antibacterial activity of PGP-C was found to be directly correlated with membrane damage mechanisms. These results indicates that P. elgii JCK-5075 producing PGPs could be used as a biocontrol agent for the control of plant bacterial diseases. This is the first report on the in vitro and in vivo antibacterial activity of PGPs against bacterial plant pathogens.

Prebiotics and probiotics are known to play beneficial roles in human nutrition and health. In this study, the effects of IPFOS-Bacillus synbiotic product, a combined prebiotic–probiotic formulation, were evaluated for digestive support and immune modulation in an animal model. Administration of IPFOS-Bacillus at doses of 37.2 mL/kg/day and 44.6 mL/kg/day significantly reduced diarrhea incidence and restored intestinal microflora balance (p < 0,05) in rats. Both doses also increased total spleen protein content (p < 0,05) and lymphocyte count in diarrheic rats. No pathological abnormalities were observed in the heart, liver, kidneys, lungs, spleen, or digestive system. These findings suggest that IPFOS-Bacillus has strong potential for development as a health protection product to be issued to soldiers.