Biofilm initiation and development is a complex process that includes several major stages. This study examined the process of Listeria monocytogenes biofilm initiation and consequent spatial and physiological patterns formed in the biofilm as the result of bacterial response to a changing environment. This is a first attempt at establishing a link between the spatial organization of biofilm-associated bacteria and major stress factors such as surface bioavailability and nutrient content. Developed linear models allow evaluation of some important parameters of the surface population, such as the critical colony size and the intercolony distance in the case of diffusion-limited nutrient access. Variations in bacterial physiological patterns during biofilm initiation as a function of bacterial population density during surface colonization are reported.

In this study the dynamics of biofilm formation on aluminum has been investigated. The process of cell growth has been observed using fluorescence microscopy. It has been confirmed that the process of biofilm formation can be represented as a sum of two separate processes: cell adhesion and colony proliferation. The derived set of equations describes kinetics of surface population growth and characteristic times for adsorption and combined growth processes, including characteristic time for the nutrient supply depletion. All equations contain variables based on the fundamental characteristics of bacterial population and can be easily determined from the experimental data or estimated theoretically. The developed theoretical model allows obtaining realistic values for population growth time and characteristic time for nutrient limitation occurrence during the biofilm development. Resulting equations qualitatively describe the biofilm formation process, and allow predicting microbial kinetics in the batch reactor system and determining critical values of the process parameters.

Microbial safety of food products is often accomplished by the formulation of food-grade preservatives into the product. Because of the growing consumer demand for natural substances (including preservatives) in the composition of consumed foods, there is also a growing interest in the natural antimicrobial nisin, which has generally recognized as safe (GRAS) status for certain applications. During the products storage time, concentrations of preservative(s) are decreasing, which may eventually cause a serious problem in the food's microbial safety. Here, for the first time we report on the non-linear response of a foodborne pathogen, Listeria monocytogenes, to sub-lethal concentrations of nisin.

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