Formation of Listeria monocytogenes Biofilm Promote by Environmental Factors
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Abstract:
The effects of environmental factors including pH, NaCl, common carbohydrates and an environmental bacteria (Ralstonia insidiosa) on the formation of biofilms by Listeria monocytogenes in normal nutrient and nutrient-poor conditions were investigated. The activity and structure of the single and double strain biofilms by Listeria monocytogenes and Ralstonia insidiosa were observed using Confocal laser scanning microscope (CLSM).The results showed that weak acid, alkaline conditions, low concentration of NaCl and Ralstonia insidiosa could significantly promote the formation of biofilm by Listeria monocytogenes. However, compared with that in normal nutrient, biofilm formation in the nutrient-poor condition was reduced. Several kinds of carbohydrates commonly found in foods (glucose, sucrose, xylitol, galactose and konjac powder) also have a certain promoting effect, especially xylitol and konjac flour, which could cause growth rates up to 75.00% and 96.67%, respectively. The results of CLSM indicated that the biofilm of Listeria monocytogenes and Ralstonia insidiosa were different, but the number of viable cells was relatively high. The formation of biofilms by pathogenic bacteria had a great threat to food safety, and many environmental factors had the effect of enhancing the formation of biofilms, which should cause concern in industries such as food production.
