auricula pigment were measured according to standard procedures (Paim et al. The physical and chemical characteristics of A. The supernatant was precipitated by the addition of 2 M HCl, washed with distilled water and lyophilized, and then stored at −20☌ for further experiments (Selvakumar et al. The precipitate was then dried at 30☌, re-dissolved in 2 M NaOH and centrifuged at 5,000 rpm for 20 min. The precipitate obtained was purified by acid hydrolysis using 6 M HCl at 100☌ for 2 h to remove carbohydrates and proteins, and treated with chloroform to wash away lipids. The supernatant was acidified with 2 M HCl to pH 2, then incubated for 12 h at 80☌. The melanin precipitates were recovered by centrifugation at 5,000 rpm for 20 min and sonicated with 300 ml 1.5 M NaOH for 1 h. After milling of dried fruiting bodies to a fine powder, 10 g dried powder was extracted using 300 ml 3 M HCl for 1 h at 60☌. Analysis of internal transcribed spacer (ITS) regions was used to determine species identification of fruiting bodies of A. Taxonomic identification of fruiting bodies was confirmed by a senior mycologist (Xin Zhentao, Institutes of Edible Mushroom, Shanghai Academy of Agricultural Sciences), based on its clearly ear-like shaped fruit bodies and its cylindrical basidia with three transverse septa (internal cross-walls dividing the hyphae). auricula produced in Liaoning province, China were purchased from a local supermarket. The three bacteria were used to determine biofilm formation and were cultured routinely in Luria-Bertani (LB) broth (0.5% yeast extract, 1% tryptone, 0.5% NaCl) at 37☌ for the exponential growth phase experiments. Escherichia coli K-12 was supplied by Nanjing Center for Disease Control and Prevention, Jiangsu province, China. fluorescens P-3 were procured from Fisheries Research Institute, Shanghai, China. fluorescens P-3 was investigated by monitoring biofilms using confocal laser scanning microscopy (CLSM). auricula fruiting bodies was characterized, and the ability of this pigment to inhibit biofilm formation of Escherichia coli K-12, Pseudomonas aeruginosa PAO1 and P. ( 2011) reported that the extracted pigments could effectively inhibit the production of violacein, a quorum-sensing (QS)-regulated behavior in Chromobacterium violaceum CV026. Nowadays, there is considerable interest in the exploitation of this fungus. These potent medicinal functions are mediated mostly by non-starch polysaccharide components, especially beta-glucans (Zhang et al. 2004), antioxidant (Finkel and Holbrook 2000 Acharya et al. 1995), hypocholesterolemia (Cheung 1996), hypoglycemic (Takeujchi et al. Auricularia auricula has been reported to have many biological activities, including antitumor (Misaki et al. From ancient times, the mushroom has been used widely in Chinese cuisine, and is known for its pharmaceutical effects in folk medicine. Novel strategies are therefore required to deal with biofilm-mediated infections.Īuricularia auricula, commonly known as ‘tree-ear’, is a species of edible mushroom found worldwide. Moreover, the resistance to antimicrobial agents of biofilm-embedded bacteria make it important to search for novel agents that can effectively kill these bacteria. However, the mechanisms by which bacteria growing in biofilms attain this resistance are still unknown. Biofilms are difficult to eradicate due to their resistant phenotype (Camilli and Bassler 2006 Domka et al. In the food industry, biofilms can be a source of recalcitrant contaminations, causing food spoilage, and are possible sources of public health problems such as outbreaks of food-borne pathogens. Biofilms can delay wound healing significantly (Percival and Cutting 2009). Bacterial attachment to surfaces and subsequent biofilm formation are important steps in the establishment of chronic infections and persistence in host tissues (Costerton et al. They cause persistent infections by forming biofilms on the surface of in vivo medical devices such as contact lens, artificial joints, and synthetic valves (Wang et al. Biofilms are a major cause of nosocomial infections. Bacteria occurring in biofilms are between 10- and 1,000-fold more resistant to antibiotics, leading to serious clinical problems, particularly regarding avoidance of host immune systems (Brooun et al. 2007), with 80% of bacterial infections being caused by biofilms (Rasmussen and Givskov 2006). These naturally existing biofilms are major threat to human beings (Wang et al. Biofilms are film-like structures formed by aggregates of bacterial cells on biotic and abiotic surfaces.
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