Biofilm formation by Staphylococcus aureus on food contact surfaces is one of the most important issues for the food safety. The difficulties in controlling biofilms have driven the search for new antibacterial and antibiofilm agents from natural resources. The aims of the present study were to investigate the antibacterial and antibiofilm activities of the methanolic extract from Zanthoxylum bungeanum Maxim. leaves and identify the active compounds. By bioassay guide of inhibitory activity against S. aureus, four antibacterial compounds were separated from this extract and identified as neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and 4-O-caffeoyl-2,3-dihydroxy-2-C-methylbutyric acid based on MS and NMR data analyses. The four compounds exhibited moderate antibacterial activity against S. aureus with minimum inhibitory concentration of 5 mg/mL. Moreover, a fraction consisted of the four compounds was subjected to antibiofilm assays against S. aureus. Crystal violet staining and XTT reduction assay demonstrated that this fraction showed an excellent inhibitory efficacy on the biomass and metabolic activity of S. aureus biofilm. Scanning electron microscopic observation displayed that this fraction induced severe morphological changes in the architecture of S. aureus biofilm, which further confirmed that it possessed a potent inhibitory activity on the biofilm formation of S. aureus. So, these results suggested that Z. bungeanum leaves could be used as an attractive and promising candidate for the development of natural antibacterial agent for controlling food-related bacterial biofilms.

Background: Soil fertility decline and pathogen infection are severe issues for crop production all over the world. Microbes as inherent factors in soil were effective in alleviating fertility decrease, promoting plant growth and controlling plant pathogens et al. Thus, screening microbes with fertility improving and pathogen controlling are great importance to humans.Results: Bacteria Pt-3 isolated from tea rhizosphere showed multiple functions in solubilizing insoluble phosphate, promoting plant growth, producing abundant volatile organic compounds (VOCs) and inhibiting the growth of important fungal pathogens in vitro. According to the 16S rRNA phylogenetic and biochemical analysis, Pt-3 was identified to be Serratia marcescens. The solubilizing zone of Pt-3 in the medium of lecithin and Ca3(PO4)2 was 2.1 cm and 1.8 cm respectively. In liquid medium and soil, the concentration of soluble phosphorus reached 343.9 mg.L-1, and 3.98 mg.kg-1, and significantly promoted the growth of maize seedling, respectively. Moreover, Pt-3 produced abundant volatiles and greatly inhibited the growth of seven important phytopathogens. The inhibition rate ranged from 75.51 to 100% respectively. Solid phase micro-extraction coupled with gas chromatography tandem mass spectrometry proved that the antifungal volatile was dimethyl disulfide. Dimethyl disulfide can inhibit the germination of Aspergillus flavus, and severely destroy the cell structures under scanning electron microscopy.Conclusions: S. marcescens Pt-3 with multiple functions will provide novel agent for the production of bioactive fertilizer with P-solubilizing and fungal pathogens control activity.

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