Effect of Temperature Fluctuation on Biofilm Formation with Bacterial Interaction between Salmonella enterica and Pseudomonas putida

Many previous studies have focused on biofilm formation of microorganisms under steady state, however, in actual environment around food, surroundings of food frequently fluctuate. This study investigated the bacterial biofilm formation and interaction between different strains under constant and fluctuating temperature conditions. Firstly, biofilm formation in mixed culture of Pseudomonas putida with Salmonella enterica under a constant temperature of 5 degree C and 30 degree C was investigated to identify the interactions between the two species. In the result, at 5 degree C, P. putida principally formed biofilm in the mixed culture with S. enterica while S. enterica could neither form biofilm nor grow well. And, an interaction between S. enterica and P. putida could not be observed at 5 degree C. In contrast, at 30 degree C, the acceleration of biofilm formation was observed under only poor nutrient condition. It can be considered that the bacterial interaction induced by a lack of nutrient accelerated biofilm formation in the mixed culture. Secondly, the effect of two different patterns of temperature fluctuation on biofilm formation in the mixed culture was studied by investigating the biofilm amount and bacterial count. In consequence, temperature fluctuation inhibited biofilm formation in the mixed culture of S. enterica with P. putida. However, salmonella count was promoted in comparison with that at the low constant temperature of 5 degree C. In summary, the stress due to a lack of nutrient caused the bacterial interaction between S. enterica and P. putida and accelerated biofilm formation in the mixed culture while fluctuating temperature had an inhibition effect on biofilm formation. However, considering the salmonella growth through temperature fluctuation, it is important to keep temperature constant during food distribution.