Characterizations of Dual-biofilms Forming by Pseudomonas lundensis and Spoilage Bacteria from Meat
The aim of the study is to explore the mixed biofilm interaction among dominant spoilage bacteria isolated from meat.The dual-biofilm characteristics of Pseudomonas lundensis and three spoilers were evaluated using by crystal violet staining,phenol sulfuric acid assay,bicinchoninic acid assay and confocal laser scanning microscope(CLSM)ob-servation at 15 ℃ and 25 ℃,as well as protease activity and disinfectant tolerance.The results showed that Pseudomonas spp.accounted for 43.5％,followed by Brochothrix thermosphacta,Acinetobacter spp.and Myriodes spp.among 23 spoil-ers isolated from beef.The amount of biofilm formation of PL,AJ and BT at 15 ℃ was significantly higher than that at 25 ℃,and levels of dual-biofilms at 15 ℃ was significantly more than single culture,indicating that low temperature significantly promoted the formation of mixed biofilm.The number of cells in biofilm co-cultured with PL and AJ was 0.75-0.78 lg(CFU/cm2),which were higher than that of single culture.Compared to PL single biofilm,the secretion of extracellular polysaccharides increased by 15.67-22.01 μg/mL,and the production of extracellular protein co-cultured with AJ or BT rose by 7.35 μg/mL and 6.70 μg/mL respectively.CLSM observation also revealed that the dual-biofilms of PL and AJ or MP formed clusters with heterogeneous structures,and their thickness of these biofilm increased to 48.99-49.22 μm.In addition,the co-culture of PL and three strains significantly enhanced its protease activity and chemical tolerance.After treatment with 0.06％sodium hypochlorite,the residual rate of dual-biofilms of PL,AJ or BT was 95.61％and 96.16％at 15 ℃,which was significantly higher than that of PL single biofilm.Thus,it was revealed that meat-derived spoilage bacteria PL and three strains formed a complex dual-biofilm with strains-dependence,and the PL cells as dual-biofilm formed at low temperature enhanced its resistance to sodium hypochlorite.This study provided a good foundation for exploring the contamination and control of mixed biofilms from meat-derived spoilage microorganisms.
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