Nutrient management is essential for the cultivation of algae and crops used for food and biofuels. In seawater and much of the world's farmable lands, providing crops with adequate nutrition is challenging because high salt and pH levels, which reduces the solubility of trace metals (such as Fe) and phosphate. While frequent application of chemical fertilizers can alleviate nutrient limitation, chelated iron fertilizers are expensive and impractical on large scales, and reserves of phosphatic rocks are limited and will be depleted within several hundred years at current mining rates. One promising sustainable solution is the enhancement of microbial processes for dissolving mineral forms of these nutrients. Our research seeks to elucidate host-microbiome interactions that can increase the bioavailability of essential nutrients and metals in order to design rational strategies for improving growth and sustainability.
Biofuel algae interactions with phycosphere bacteria
Maintaining metal homeostasis is essential for the growth of bioenergy relevant photosynthetic algae and the efficiency of CO2 conversion into useful organic molecules. In aquatic environments, algae and their associated microbiome invest significant energy into producing and secreting organic molecules that chelate metals in order to solubilize and facilitate uptake of micronutrients and detoxify harmful toxins. These chelating agents act as public goods that can drive community dynamics and interspecies interactions within a population. We seek to understand and predict the effect of metal stress on microbial community stability and biomass production by characterizing the specific metabolic interactions between taxa that regulate the cycling of metal, nutrients, and carbon in biofuel production systems. Our goal is to identify symbiotic metabolic interactions that shape the phycosphere microbiome and that can ultimately be exploited to improve the resiliency of biofuel mesocosms to abiotic and biotic stress. We aim to determine the sources and identities of chelating agents that govern metal cycling in a multi-taxa community and evaluate beneficial or detrimental effects on other organisms within the population. This project is a collaboration with the Biofuels Science Focus Area at the Lawrence Livermore National Laboratory. https://bio-sfa.llnl.gov/
How do the interactions between plants and microbes adapt to iron deficiency?
Nutrient mobilization from soil minerals is critical for plant growth, particularly in marginal lands with high pH soils or low phosphate availability. One way that rhizospheric bacteria enhance plant growth is by converting root exudates such as sugars and amino acids into organic acids and chelating molecules that enhance mineral dissolution and improve the availability micronutrient iron. We are currently studying the effect of iron availability on metabolite exchange between the model grass Brachypodium distachyon and the rhizosphere bacteria Pseudomonas fluorescens and Bacillus subtillis. When trace metal availability is low, Brachypodium alters the composition of exudates to increase production of metabolites and organic acids that mediate metal uptake. In this project, we are addressing questions regarding which metabolic strategies for iron conservation and acquisition (e.g. siderophore and organic acid production by plants or rhizospheric bacteria) are activated under well defined growth condition. We seek to develop metabolic models that can help us predict the effect of microbes on plant iron nutrition under different environmental conditions.