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Significance and Impact of the Study: Bacillus subtilis and harpins are biological control agents with respective advantages. In this study, combinations of the both were applied to tomato in the form of hpaG Xooc -expressing B. subtilis, showed much better effects on resistance to wilt disease, and equivalent effects on plant growth promotion compared with the progenitor strain have a great potential in agricultural use. AbstractBoth Bacillus subtilis and harpins stimulate plant growth and defence against various plant pathogens. In this study, B. subtilis 168 and two derivatives, surfactin producer OKB105 and combined surfactin and HpaG Xooc producer OKBHF, were applied to tomato plants to investigate the mechanisms underlying this effect. To evaluate colonization ability, strains were labelled with green fluorescent protein (GFP). Although biofilm distribution of the three strains was similar on root surfaces, Colonization populations of the two surfactin producers were approximately 2-to 3-fold higher than that of strain 168, and this was accompanied by significantly increased tomato growth. These results suggest that efficient colonization, possibly facilitated by surfactin production, enhanced the efficiency of plant growth promotion by B. subtilis. All three B. subtilis treatments caused plants to have less severe disease symptoms after inoculation with Ralstonia solanacearum, with plants treated with OKBHF being the most resistant, suggesting that hpaG Xooc improves biocontrol efficiency of B. subtilis. Analysis of defence-related genes showed a synergistic effect of HpaG Xooc on B. subtilis enhancement of the expression of the pathogenesis-related genes PR1b1 and PR-P2. In contrast, expression of the defence-related genes PINI and PINII was suppressed.

This experiment was conducted to evaluate the impact of yeast and lactic acid bacteria (LAB) on mastitis and milk microbiota composition of dairy cows. Thirty lactating Holstein cows with similar parity, days in milk were randomly assigned to five treatments, including: (1) Health cows with milk SCC < 500,000 cells/mL, no clinical signs of mastitis were found, fed basal total mixed ration (TMR) without supplementation (H); (2) Mastitis cows with milk SCC > 500,000 cells/mL, fed basal TMR without supplementation (M); (3) Mastitis cows fed basal TMR supplemented with 8 g day −1 yeast (M + Y); (4) Mastitis cows fed basal TMR supplemented with 8 g day −1 LAB (M + L); (5) Mastitis cows (milk SCC > 500,000 cells/mL) fed basal TMR supplemented with 4 g day −1 yeast and 4 g day −1 LAB (M + Y + L). Blood and milk sample were collected at day 0, day 20 and day 40. The results showed efficacy of probiotic: On day 20 and day 40, milk SCC in H, M + Y, M + L, M + Y + L was significantly lower than that of M (P < 0.05). Milk concentration of TNF-α, IL-6 and IL-1β in M + Y + L were significantly reduced compared with that of M on day 40 (P < 0.05). Milk Myeloperoxidase (MPO) and N-Acetyl-β-d-Glucosaminidase (NAG) activity of M + Y, M + L, M + L + Y were lower than that of M on day 40 (P < 0.05). At genus level, Staphylococcus, Chryseobacterium and Lactococcus were dominant. Supplementation of LAB decreased abundance of Enterococcus and Streptococcus, identified as mastitis-causing pathogen. The results suggested the potential of LAB to prevent mastitis by relieving mammary gland inflammation and regulating milk microorganisms.