Spatial segregation and cooperation in radially expanding microbial colonies under antibiotic stress

Abstract

Antibiotic resistance in microbial communities reflects a combination of processes operating at different scales. In this work, we investigate the spatiotemporal dynamics of bacterial colonies comprised of drug-resistant and drug-sensitive cells undergoing range expansion under antibiotic stress. Using the opportunistic pathogen Enterococcus faecalis with plasmid-encoded β-lactamase, we track colony expansion dynamics and visualize spatial patterns in fluorescently labeled populations exposed to antibiotics. We find that the radial expansion rate of mixed communities is approximately constant over a wide range of drug concentrations and initial population compositions. Imaging of the final populations shows that resistance to ampicillin is cooperative, with sensitive cells surviving in the presence of resistant cells at otherwise lethal concentrations. The populations exhibit a diverse range of spatial segregation patterns that depend on drug concentration and initial conditions. Mathematical models indicate that the observed dynamics are consistent with global cooperation, despite the fact that β-lactamase remains cell-associated. Experiments confirm that resistant colonies provide a protective effect to sensitive cells on length scales multiple times the size of a single colony, and populations seeded with (on average) no more than a single resistant cell can produce mixed communities in the presence of the drug. While biophysical models of drug degradation suggest that individual resistant cells offer only short-range protection to neighboring cells, we show that long-range protection may arise from synergistic effects of multiple resistant cells, providing surprisingly large protection zones even at small population fractions.

Contribution of the genomic and nutritional differentiation to the spatial distribution of bacterial colonies

“…Studies on the growth of single colonies observed that colony growth was dependent on the nutritional condition, agar concentration and presence of other cells ( Harcombe et al, 2014 ; Warren et al, 2019 ; Díaz-Pascual et al, 2021 ). The colony growth pattern and dynamics could be perturbed by spatial antibiotics in the growth environment ( Frost et al, 2018 ; Sharma and Wood, 2021 ), which might be caused by physical and mechanical interactions ( Persat et al, 2015 ; Tronnolone et al, 2018 ). Despite many studies linking environmental conditions to colony growth patterns ( van Gestel et al, 2014 ; Cole et al, 2015 ; Xiong et al, 2020 ), the spatial distribution of colony size has rarely been reported.…”

Social evolution of shared biofilm matrix components

“…Finally, previous work has shown that in the cases of extracellular enzymes ( 27 , 70 , 71 ), siderophores ( 23 , 72 ), and autoinducers ( 73 – 75 ) as diffusive public goods, clonal segregation and efficient consumption of public goods (or their enzymatic products and complexes) through high local cell density and a high uptake rate can minimize the potential for exploitation in the context of continuous films ( 21 , 26 , 27 ). In the context of spatially discrete clonal clusters, we expect the evolutionary stability of these public goods to be determined by the interplay between the exploitation range and the spatial structure as shown here.…”

Assessing Antibiotics Biodegradation and Effects at Sub-inhibitory Concentrations by Quantitative Microbial Community Deconvolution

“…However, even here opportunistic community members seemed to profit from background AOC and produce (micro-)colonies, despite the selective presence of the antibiotic as sole carbon and energy source. Such opportunistic growth might have also been possible with synergistic effects of resistant cells protecting those sensitive cells from antibiotics (Sharma and Wood, 2021). Potential avenues to enrich further for antibiotics degraders at low concentrations might be to deploy slow sand filter columns as in earlier selection studies with chlorinated compounds in the μg l −1 range (van der Meer et al, 1987) or adapt enrichment under flow to specifically designed microfluidics platforms e.g.…”