Burst statistics in an early biofilm quorum sensing model: the role of spatial colony-growth heterogeneity

Abstract

Quorum-sensing bacteria in a growing colony of cells send out signalling molecules (so-called “autoinducers”) and themselves sense the autoinducer concentration in their vicinity. Once—due to increased local cell density inside a “cluster” of the growing colony—the concentration of autoinducers exceeds a threshold value, cells in this clusters get “induced” into a communal, multi-cell biofilm-forming mode in a cluster-wide burst event. We analyse quantitatively the influence of spatial disorder, the local heterogeneity of the spatial distribution of cells in the colony, and additional physical parameters such as the autoinducer signal range on the induction dynamics of the cell colony. Spatial inhomogeneity with higher local cell concentrations in clusters leads to earlier but more localised induction events, while homogeneous distributions lead to comparatively delayed but more concerted induction of the cell colony, and, thus, a behaviour close to the mean-field dynamics. We quantify the induction dynamics with quantifiers such as the time series of induction events and burst sizes, the grouping into induction families, and the mean autoinducer concentration levels. Consequences for different scenarios of biofilm growth are discussed, providing possible cues for biofilm control in both health care and biotechnology.

Controlled spatial organization of bacterial clusters reveals cell filamentation is vital forXylella fastidiosabiofilm formation

“…The concept of cell density-dependent changes in cell behavior and phenotypes by DSFbased quorum sensing might underlie our observed cell density-dependent initiation of filamentous cell morphogenesis and directional cell growth 11,34,64 . In further support to this conjecture, previous observations in X. fastidiosa as well as in other bacteria and human cells have shown that quorum sensing mechanisms are activated upon exceeding a local DSF concentration threshold at regions of high cell densities 37,59,[65][66][67] Consistent with this model, a previous study using a X. fastidiosa…”

Spatial Correlations and Distribution of Competence Gene Expression in Biofilms of Streptococcus mutans

“… Aspiras et al (2004) suggested that comX expression may be localized to small clusters of cells, occupying discrete microniches that provide favorable conditions of cell density, nutrient and other factors. Modeling studies have also anticipated spatial correlations or clustering in quorum activity inside bacterial biofilms ( Hense et al, 2007 ; Kindler et al, 2019 ).…”

Spatial correlations and distribution of competence gene expression in biofilms ofStreptococcus mutans

“…Aspiras et al suggested that comX expression may be localized to small clusters of cells, occupying discrete microniches that provide favorable conditions of cell density, nutrient and other factors. Modeling studies have also anticipated spatial correlations or clustering in quorum activity inside bacterial biofilms (Hense et al, 2007;Kindler et al, 2019). Diffusion in biofilms is affected by molecular charge and mass, interactions with biofilm constituents, and by the porosity of the biofilm (Stewart, 2003;Marcotte et al, 2004;Zhang et al, 2011).…”

“…Aspiras et al suggested that comX expression may be localized to small clusters of cells, occupying discrete microniches that provide favorable conditions of cell density, nutrient and other factors. Modeling studies have also anticipated spatial correlations or clustering in quorum activity inside bacterial biofilms (Hense et al, 2007; Kindler et al, 2019).…”