Environment specific growth inhibition by a pSymA-encoded siderophore.

<p>Growth of the ΔpSymAB strain is inhibited by a siderophore produced by the wild type (left stab) when grown in TY medium (<b>A</b> – left panel), but not if the overlay is supplemented with 150 µM FeCl₃ (<b>A</b> – right panel). This inhibition fails to occur when the siderophore biosynthesis genes are knocked out in the wild type, as is the case in <i>S. meliloti</i> RmFL2950 (58) (right stab). (<b>B</b>) When co-inoculated in the same soil mesocosm, the ΔpSymA strain easily outcompetes the wild type, and the wild type fails to inhibit growth of the ΔpSymA strain. Data points represent averages of duplicate samples, while error bars represent the range from duplicate samples. Solid lines indicate growth pattern during co-inoculation, while dotted lines indicate growth pattern when individually inoculated. Blue – wild type; red –ΔpSymA.