Phosphobacteria as key actors to overcome phosphorus deficiency in plants

Abstract

Phosphorus (P), an essential macronutrient for all living organisms, is required in large amounts for the growth and development of plants. Although total soil P level is high, P bioavailability to plants is suboptimal in most soils because of high fixation rates into inorganic and organic insoluble complexes. Hence, plants are highly dependent on mechanisms that allow them to adapt to low-phosphate stress and/or achieve suitable levels of soluble P on the root surface. In this regard, the rhizospheric microbiota plays a key role in facilitating P nutrition and has long been recognised for their potential use as an environmental-friendly alternative to chemical P fertilisation. Herein, we outline the advances in the identification of phosphate solubilising bacteria and phosphate mineralising bacteria, collectively known as phosphobacteria, and their role in rendering P accessible to plants. We review and discuss research progress related to the introduction of phosphobacteria and/or P-mineralising enzymes into soil, as well as plant transformation with bacterial genes that encode such enzymes, as strategies to improve plant growth and P nutrition. We also provide an overview of studies about the impact of variations in soil P levels on the structure of soil and rhizospheric microbial communities and the potential consequences of such perturbations on plant growth. Finally, we discuss possible directions for future research to optimise the efficiency of biofertilisation strategies based on the use of phosphobacteria.