INFLUENCE OF STRUCTURAL-PROPERTIES AND KINETIC CONSTRAINTS ON BACILLUS-CEREUS GROWTH

The influence of structural properties and kinetic constraints on the behavior of Bacillus cereus was investigated on agar media, Dimensiona l criteria were used to study the growth in bacterial colonies, The ar chitecture of the agar gel as modified by the agar content was found t o influence the colony size, and smaller colonies were observed on med ia containing 50 to 70 g of agar liter(-1). Except at low nutrient lev els, colonies responded to nutrient gradients by decreasing in size th e farther away they were from the nutrient source, and the decrease in colony size was influenced by the agar content. The diffusivities of glucose and a protein (insulin like growth factor) were not affected b y the gel architecture, suggesting that other factors, such as mechani cal factors, could influence microbial growth in the agar systems used . Increasing the viscosity of the liquid phase of the agar media by ad ding polyvinylpyrrolidone resulted in a reduction in colony size. When the agar concentration was increased, the colony areas were not influ enced by the viscosity of the system.