Fig. 5
Direct competition between pyoverdine producers and non-producers reveal both cheating behaviour and resistance to cheating. a When grown as monocultures, the eight pyoverdine non-producers grew significantly worse than the pyoverdine producers, showing that the inability to produce pyoverdine represents a handicap in iron-limited CAA medium. Growth of non-producers (red triangles) tagged with a neutral constitutive mCherry marker was compared to growth of the strains producing a pyoverdine type that can (orange diamonds) or cannot (grey circles) be used by the respective non-producers for iron uptake. Data points show means ± 95% confidence intervals across three replicates. b Direct competition between non-producers and producers revealed three different scenarios. When competing against producers that secrete a compatible pyoverdine (orange diamonds), non-producers could win the competition in four cases. In the other four cases, non-producers could not outcompete producers despite being able to use the producer’s pyoverdine. Finally, when competing against producers that secrete an incompatible pyoverdine (grey circles), non-producers were always strongly outcompeted. The dashed line depicts fitness parity, whereas values greater or smaller than zero indicate cases where non-producers or producers won the competition, respectively. While symbols show individual data points, bars depict means across six replicates. Data were ln-transformed prior to analysis
