DOI: 10.5061/dryad.h5fg1
title: Data from: Pleiotropy and the low cost of individual traits promote cooperation

description: The evolution of cooperation is thought to be promoted by pleiotropy,
 whereby cooperative traits are co-regulated with traits that are important
 for personal fitness. However, this hypothesis faces a key challenge: what
 happens if mutation targets a cooperative trait specifically rather than
 the pleiotropic regulator? Here we explore this question with the
 bacterium Pseudomonas aeruginosa, which cooperatively digests complex
 proteins using elastase. We empirically measure and theoretically model
 the fate of two mutants – one missing the whole regulatory circuit behind
 elastase production and the other with only the elastase gene mutated –
 relative to the wild-type. We first show that, when elastase is needed,
 neither of the mutants can grow if the wild-type is absent. And,
 consistent with previous findings, we show that regulatory gene mutants
 can grow faster than the wild-type when there are no pleiotropic costs.
 However, we find that mutants only lacking elastase production do not
 outcompete the wild-type, because the individual cooperative trait has a
 low cost. We argue that the intrinsic architecture of molecular networks
 makes pleiotropy an effective way to stabilize cooperative evolution.
 While individual cooperative traits experience loss-of-function mutations,
 these mutations may result in weak benefits, and need not undermine the
 protection from pleiotropy.
description: CFUs of mixes of strains
 in CAA and BSA at 0 and 48 hoursPopulation sizes of each
 of the strains (wildtype WT, lasB mutants DLB and lasR mutants DLR) were
 quantified in monoculture and in coculture at different ratios of WT to
 mutant (9:1, 1:1 or 1:9). Experiments were conducted in two growth media:
 CAA (casamino acids + M9), which all strains could take up and BSA
 (casamino acids + M9 + BSA, which could only be digested using elastase).
 To distinguish the strains in cocultures, fluorescently-labelled strains
 (YFP or DsRed) were used and mixed in all possible combinations to test
 for labelling effects. We quantified population sizes by plating out
 dilution series and counting colony-forming units. These are listed in the
 file for t=0h and t=48h. This shows how the ratio of the strains and the
 total population size change throughout the experiment. These data were
 used to generate Fig. 1B, 2B and 3.CFUs_CAA_BSA_0h_48h.xlsxGrowth curves (OD_600) over 48 hours in CAA mediumPopulation sizes of each of all experimental treatments (monocultures of wildtype WT, lasB mutants DLB and lasR mutants DLR) and cocultures of WT and one of the mutants at different ratios (9:1, 1:1 or 1:9) growing in CAA medium (casamino acids, which all strains should be able to take up). We quantified population sizes using a Tecan plate reader measuring OD_600. These are listed in the file every hour for 48 hours. These data were used to generate Fig. 1A.growth_curves_CAA.xlsxGrowth curves (OD_600) over 48 hours in BSA mediumPopulation sizes of each of all experimental treatments (monocultures of wildtype WT, lasB mutants DLB and lasR mutants DLR) and cocultures of WT and one of the mutants at different ratios (9:1, 1:1 or 1:9) growing in BSA medium (casamino acids with BSA, which can only be degraded by elastase). We quantified population sizes using a Tecan plate reader measuring OD_600. These are listed in the file every hour for 48 hours. These data were used to generate Fig. 2A.growth_curves_BSA.xlsx