Mathematical Modeling of Escherichia coli and Lactobacillus acidophilus Growth Based on Experimental Mixed Batch Cultivation

A better understanding of cultivation of microorganisms in mixed culture is needed to identify the relationships between different bacterial strains. <i>Lactobacillus acidophilus</i> (ATCC 4796) Gram-positive bacteria and <i>Escherichia coli</i> (K12-MG1655) Gram-negative bacteria are two microorganisms that can interact accidentally in the dairy food chain process or in different human pathologies. This work focused on how bacterial populations evolve in batch culture, depending on the nature of the carbon source, by monitoring cell viability using flow cytometry and substrate concentration. The experiments monitored the time evolution of bacterial populations grown on two different cultivation media (single source of carbon-SSCM and de Man, Rogosa and Sharpe-MRS broth media) which stimulated different proliferation conditions. Experimental data were used to calibrate a segregated mathematical model (accounting for two bacterial strains-biological clusters-with their individual birth time, an event that creates a new timeline cluster to which daughters belong) that highlights in silico the various interactions that can occur between two bacterial species.