Streptomyces volatile compounds influence exploration and microbial community dynamics by altering iron availability

ABSTRACT Bacteria and fungi produce a wide array of volatile organic compounds (VOCs), and these can act as infochemicals or as competitive tools. Recent work has shown that the VOC trimethylamine (TMA) can promote a new form of Streptomyces growth, termed ‘exploration’. Here, we report that TMA also serves to alter nutrient availability in the area surrounding exploring cultures: TMA dramatically increases the environmental pH, and in doing so, reduces iron availability. This, in turn, compromised the growth of other soil bacteria and fungi. In contrast, Streptomyces thrives in these iron-depleted niches by secreting a suite of differentially modified siderophores, and by upregulating genes associated with siderophore uptake. Further reducing iron levels by siderophore piracy, limiting siderophore uptake, or growing cultures in the presence of iron chelators, unexpectedly enhanced exploration. Our work reveals a new role for VOCs in modulating iron levels in the environment, and implies a critical role for VOCs in modulating the behaviour of microbes and the makeup of their communities.