Metabolic interdependence drives genetic mixing.

Abstract

<p>Producer segregation index (<i>s</i>_A, see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003398#s4" target="_blank">Methods</a>) for varying by-product toxicity and degree of cross-feeder obligacy when the two species compete for both nutrients and space <b>A,</b> or compete for space only <b>E.</b> Lighter regions indicate greater mixing (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003398#s4" target="_blank">Methods</a> for further details and <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003398#pcbi.1003398.s005" target="_blank">fig. S5</a> for cross-feeder segregation index). Data are the mean of 3 replicates. <b>B–D, F, G.</b> Biofilm images of community growth from one of the associations represented in <b>A</b> or <b>E</b>. Producer is represented in red, and facultative cross-feeder, obligate cross-feeder, and non-cross-feeder are represented in blue. By-product is in gray. The schematics illustrate the metabolic interaction scenarios. Oval, hexagon, and triangle, represent bacteria, main nutrient, and by-product, respectively. Open arrows represent a positive effect, whereas oval arrows represent a negative effect upon the population or resource they are pointing toward. See <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003398#pcbi.1003398.s001" target="_blank">fig. S1</a> for a complete schematic representation of all metabolic interaction scenarios.</p