P-324 - Unraveling competition-based niche selection within the citrus microbiome

Native microbial members are key participants in the interplay between plant pathogens and their hosts. Investigating these microbe-associated interactions is essential for developing effective biocontrol methods for commercial crops, such as citrus. By developing a germ-free micropropagation system, we show microbial members impose plant tissue niche selection by competition of essential resources, like iron. Using a reduced microbiome containing four key citrus-associated microbes: Bacillus simplex, Klebsiella aerogenes, Cronobacter sakazakii, and Burkholderia cepacia, we performed in vitro and in planta assays to characterize the effects of inter-microbe interactions. These bacteria can selectively colonize plant tissues and we find their colonization patterns are disrupted in the presence of other microbes. Whole-genome sequencing identified iron-capturing siderophores as a possible mechanism for their competition. The ability to produce these high affinity iron binding siderophores allows bacteria to advantageously colonize low-iron environments like the plant phyllosphere. Thus, identifying the molecular basis for how microbes interact within their niche can aid development of effective biological controls.