  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.
