Microbe-Metal-Mineral Interactions

Overview

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.

How do siderophores produced by fungi enhance nutrient uptake of switchgrass?

Participant: Ikumi

Switchgrass is a leading candidate for renewable biofuel production, but its long-term sustainability depends on reducing fertilizer inputs like nitrogen, phosphorus, and iron. Our research explores how root-associated fungi help switchgrass access iron through the secretion of specialized molecules called siderophores. Different fungal strains produce distinct siderophores, some of which significantly boost iron levels in plant shoots. By identifying and characterizing these compounds, we aim to uncover how fungal partnerships can enhance nutrient uptake naturally. This work helps guide the selection of beneficial microbes to reduce chemical inputs and improve the environmental footprint of biofuel agriculture.

Pictures from Ikumi: fungi and switchgrass!

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.

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