Turning the Table: Plants Consume Microbes as a Source of Nutrients

Abstract

Interactions between plants and microbes in soil, the final frontier of ecology, determine the availability of nutrients to plants and thereby primary production of terrestrial ecosystems. Nutrient cycling in soils is considered a battle between autotrophs and heterotrophs in which the latter usually outcompete the former, although recent studies have questioned the unconditional reign of microbes on nutrient cycles and the plants' dependence on microbes for breakdown of organic matter. Here we present evidence indicative of a more active role of plants in nutrient cycling than currently considered. Using fluorescent-labeled non-pathogenic and non-symbiotic strains of a bacterium and a fungus (Escherichia coli and Saccharomyces cerevisiae, respectively), we demonstrate that microbes enter root cells and are subsequently digested to release nitrogen that is used in shoots. Extensive modifications of root cell walls, as substantiated by cell wall outgrowth and induction of genes encoding cell wall synthesizing, loosening and degrading enzymes, may facilitate the uptake of microbes into root cells. Our study provides further evidence that the autotrophy of plants has a heterotrophic constituent which could explain the presence of root-inhabiting microbes of unknown ecological function. Our discovery has implications for soil ecology and applications including future sustainable agriculture with efficient nutrient cycles.

The mixotrophic nature of photosynthetic plants

“…5d; Prieto et al 2011;Mercado-Blanco and Prieto 2012). Our research indicates that uptake of protein, DNA and microbes appears to be restricted to root-hairproducing trichoblasts (Paungfoo- Lonhienne et al 2008Lonhienne et al , 2010aLonhienne et al , 2010b (Fig. 5a-c).…”

“…We tested this possibility and presented the first evidence that root cells incorporate nonpathogenic and non-symbiotic microbes as nutrient sources (Fig. 3;Paungfoo-Lonhienne et al 2010b). As microbes compete with plants for soil nutrients, uptake and digestion of microbes could be an adaptation for securing nutrients (Paungfoo-Lonhienne et al 2010b).…”

“…3;Paungfoo-Lonhienne et al 2010b). As microbes compete with plants for soil nutrients, uptake and digestion of microbes could be an adaptation for securing nutrients (Paungfoo-Lonhienne et al 2010b).…”

Evaluation of Bacterial Strains for the Induction of Plant Biochemicals, Nutritional Contents and Isozymes in Barley

“…To minimize these challenges plants and microbes sometimes build a mutual relationship between them to benefit each other. However, very rarely it has seen that microbes use plants as host to invade them for their life cycle completion and parallel plants eat microbes identified as intruder as reported in recent study by Paungfoo-Lonhienne et al [2]. In most of the cases plants and microbes develop symbiotic relationship where they do not cause pathogenicity to each other and develop bilateral combination to benefit each other as a host medium.…”

From Dust Bowl to Dust Bowl: Soils are Still Very Much a Frontier of Science

“…Among this plethora of appropriations of the concept of final frontier for a wide variety of purposes, a few articles have put forth that soils, or at least some of their characteristics (e.g., Ramanathan et al, 2006;Paungfoo-Lonhienne et al, 2010), should be considered "the" genuine final frontier. A 1995 feature article in The Independent, for example, advocated that the biodiversity of soils is essential to mankind, yet most of the life forms present in soils are still utterly unknown: "we are left with a living world of which we know next to nothing.…”