Cross-feeding drives mixing, allowing susceptible cells to benefit from the antibiotic detoxification by neighbouring resistant cells.

Abstract

<p><b>A.</b> S cells grow in coculture with non-detoxifying R cells (dashed line) or with antibiotic-detoxifying R cells (filled line) under high antibiotic conditions. The two types are seeded either in a randomly mixed or segregated manner (see <b>C</b> for images of seeding at t = 0h). <b>B.</b> Segregation index of communities shown in <b>A</b> when seeded in a randomly mixed (bottom line, with segregation index ~0 at t = 0) or segregated (top line, with segregation index ~1 at t = 0) manner (for segregation index description, see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1006179#sec007" target="_blank">Methods</a>). Mutualistic communities generally tend to mix while competitive communities tend to segregate. The two ‘alternative’ outcomes of segregation pattern observed for the competition and non cross-feeding cases occur because the potential for species mixing or segregation depends on a lineage ability to grow. This means that, if the susceptible cells start mixed and are unable to grow- such as with high antibiotics, they will inevitably remain mixed as they cannot grow into segregated clusters of susceptible cells. <b>C.</b> Images show representative examples of simulations from one of the scenarios represented in <b>A</b> at t = 0h (seeding) and after 6h, 8h, 12h, and 18h growth for the case when the resistant strain is detoxifying (see also <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1006179#pcbi.1006179.s009" target="_blank">S1</a>–<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1006179#pcbi.1006179.s012" target="_blank">S4</a> Movies).</p