Emergence of cooperativity in a model biofilm

Abstract

Evolution to multicellularity from an aggregate of cells involves altruistic cooperation between individual cells, which is in conflict with Darwinian evolution. How cooperation arises and how a cell community resolves such conflicts remain unclear. In this study, we investigated the spontaneous emergence of cell differentiation and subsequent division of labour in evolving cellular metabolic networks. In spatially extended cell aggregates, our findings reveal that resource limitation can lead to the formation of subpopulations and cooperation of cells, and hence multicellular communities. A specific example of our model can explain the recently observed oscillatory growth in Bacillus subtilis biofilms.

Differential equation-based minimal model describing metabolic oscillations in Bacillus subtilis biofilms

“…To understand biofilms more closely and make predictions based on empirical data, several models have been developed [4,[7][8][9][10][11][12]. Liu et al [4] observed oscillations in the biofilm, which they explained by different metabolic roles performed by the different compartments in the biofilm.…”

Smartphone-Based Whole-Cell Biosensor Platform Utilizing an Immobilization Approach on a Filter Membrane Disk for the Monitoring of Water Toxicants

“…These findings are supported by previously reported results that showed evidence for enhanced sensitivity in surface-bound E. coli strain AB725 as compared to suspended ones when tested with genotoxicant nalidixic acid [ 12 ]. The explanation behind this higher sensitivity might be the cooperativity between the immobilized bacteria cells, which maximizes the bioluminescence signal output when exposed to environmental toxicants [ 15 , 44 , 45 ]. It was previously reported that the transition of bacterial cells from a free-swimming state to adsorption on surfaces might lead to changes in their cellular responses as well as to cooperative behavior between the bacteria cells, due to the limitation of nutrients [ 44 ].…”

“…The explanation behind this higher sensitivity might be the cooperativity between the immobilized bacteria cells, which maximizes the bioluminescence signal output when exposed to environmental toxicants [ 15 , 44 , 45 ]. It was previously reported that the transition of bacterial cells from a free-swimming state to adsorption on surfaces might lead to changes in their cellular responses as well as to cooperative behavior between the bacteria cells, due to the limitation of nutrients [ 44 ]. From the results, the highest sensitivity was observed at the bacteria cells concentration at an optical density of 0.2 (OD 600 ).…”

“…It is possible that the interactions between the bacteria cells in higher density might compensate for the loss of bacterial viability that results from the lack of water and nutrient during the storage period. More importantly, the higher density of bacteria may enhance the interaction between the cells and thereby maintain the stability of the bacterial population [ 44 , 46 ]. To conclude, the immobilization of the bioreporter bacteria at an optical density of 0.8 (OD 600 ) on the filter membrane disk demonstrated higher sensitivity to ethanol and also maintained better stability during storage; therefore, it was chosen as the preferred bacterial density for subsequent analysis.…”