Abstract
Microorganisms that release plant-available phosphate from natural soil phosphate stores may serve as biological alternatives to costly and environmentally damaging phosphate fertilizers. To explore this possibility, we engineered a collection of root bacteria to release plant-available orthophosphate from phytate, an abundant phosphate source in many soils. We identified 82 phylogenetically diverse phytase genes, refactored their sequences for optimal expression in Proteobacteria, and then synthesized and engineered them into the genomes of three root-colonizing bacteria. Liquid culture assays revealed 41 engineered strains with high levels of phytate hydrolysis. Among these, we identified 12 strains across three bacterial hosts that confer a growth advantage on the model plant Arabidopsis thaliana when phytate is the sole phosphate source. These data demonstrate that DNA synthesis approaches can be used to generate plant-associated strains with novel phosphate-solubilizing capabilities.IMPORTANCE Phosphate fertilizers are essential for high-yield agriculture yet are costly and environmentally damaging. Microbes that release soluble phosphate from naturally occurring sources in the soil are appealing, as they may reduce the need for such fertilizers. In this study, we used synthetic biology approaches to create a collection of engineered root-associated microbes with the ability to release phosphate from phytate. We demonstrate that these strains improve plant growth under phosphorus-limited conditions. This represents a first step in the development of phosphate-mining bacteria for future use in crop systems.
Highlights
Microorganisms that release plant-available phosphate from natural soil phosphate stores may serve as biological alternatives to costly and environmentally damaging phosphate fertilizers
Generation of transgenic bacterial strains overexpressing a diversity of phytases
We aimed to create a collection of plant-associated Pi-releasing bacteria by engineering diverse Pi-liberating enzymes into the genomes of multiple host bacteria (Fig. 1)
Summary
Microorganisms that release plant-available phosphate from natural soil phosphate stores may serve as biological alternatives to costly and environmentally damaging phosphate fertilizers To explore this possibility, we engineered a collection of root bacteria to release plant-available orthophosphate from phytate, an abundant phosphate source in many soils. We used synthetic biology approaches to create a collection of engineered root-associated microbes with the ability to release phosphate from phytate We demonstrate that these strains improve plant growth under phosphorus-limited conditions. Plants and soil microorganisms have evolved diverse mechanisms to obtain phosphate from existing sources in the soil These include expression of phosphatase and phytase enzymes to release Pi from organic phosphates [8] and exudation of organic acids and siderophores to solubilize inorganic phosphate [9,10,11]. It may be useful to develop several engineered bacterial strains, which could be used in a customized manner depending on crop and environment
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