We are interested in small-molecule-level interactions between microbes, primary producers (plants or phytoplankton), and the environment. Using chemical approaches in a biological context, we characterize and profile important groups of secreted metabolites to understand their impact on biogeochemical cycles, crop productivity, and human health. These exometabolomes are released by microorganisms, plants, and insects in response to interactions with their abiotic and biotic environment and include secondary metabolites, carbohydrates, lipids, nucleic acids, organic acids, peptides, enzymes, and other bioactive molecules. Their functions range from accessing essential nutrient resources and sequestration of heavy metals over communication to regulation of plant growth and chemical competition with pathogens. Microbial communities and their interactions with the abiotic and biotic environment are incredibly complicated.
Our research is informed by an understanding of the universal importance of trace-metal limitation or toxicity as a bottom-up control on microbial communities and their interactions with plants or phytoplankton. Trace metals are essential for cellular growth: they act as catalytic centers in enzymes and provide chemical structure. The availability of some, especially ferric iron, can limit growth and microbial nitrogen fixation. Although iron is a major constituent in the earth crust, it is extremely insoluble at neutral pH values. The universal importance of iron as a limiting micro-nutrient can be observed in the oceans, in terrestrial environments, and in the struggle of pathogens to infect hosts. Thus, trace-metals can shape microbial communities and their interactions via secreted small-molecules.
Advances in genomic analysis have revealed unsuspectedly rich and complex microbiomes in close association with plants, phytoplankton, and other environmental niches. The chemistry and mechanism of microbial interactions through exometabolomes, however, remain mostly in the dark. The reason is that the vast majority of microbes cannot be cultured and analyzing the extreme complexity of mixtures of molecules with orders of magnitude differences in concentrations and activities is a challenge. Our studies make use innovative analytical approaches and rapid instrumental developments for profiling and characterization of small molecules in plant-microbe-insect interactions in the environment and in agriculture.