Quorum Sensing as a long-range interaction for bacteria growth and bioluminescence

We study the role of Quorum Sensing (QS) in the growth of bacterial colonies and in the bioluminescence produced. These two phenomena are both regulated by QS and the experimental data show a non-trivial correlation between them. It is also known that the specific bacterial substrate potentially modifies the behavior of the colony. In the specific case of the bioluminescent gram-negative bacterium, Vibrio harveyi, we propose a three-autoinducer model in which QS is described in terms of long-range interaction between charged objects placed on a regular network and playing the role of bacteria. The charges spread in the network through fictitious non-linear electrostatic interactions. QS is monitored by analyzing the current flowing within the network. The model parameters are determined by comparing the simulations with the data present in the literature and related to liquid cultures. New colony growth measurements are then performed on Vibrio campbelli (a member of the clade Harveyi) grown on hydroxyapatite (HA) substrates relevant for biomedical applications. Growth on the substrate differs from growth in liquid culture, although the observed bioluminescence is similar. We exploit our model to understand the differences between colonies in liquid culture and on substrate in terms of the relative role and cooperation of the three autoinducers.