Modification of rhizobacterial populations by engineering bacterium utilization of a novel plant-produced resource

Abstract

The ability to catabolize distinct nutrients produced by a plant may be a factor in the successful colonization of that host by a bacterium when in competition with other rhizosphere microorganisms. We tested this hypothesis by examining the influence of a novel substrate produced by a transgenic plant on root colonization by near-isogenic bacteria, differing only in their ability to use the resource. When inoculated alone, both bacteria colonized the roots of the normal and transgenic plants with equal kinetics and to indistinguishable levels. When the two bacteria were coinoculated, the catabolizer reached a population density significantly higher than that of the noncatabolizer on the roots of the resource-producing plant. No such advantage was observed on the roots of normal plants. These results support the theory that resources produced and exuded by a plant host can confer a selective advantage to microorganisms that use the substrate.

Enhancement of Plant-Microbe Interactions Using a Rhizosphere Metabolomics-Driven Approach and Its Application in the Removal of Polychlorinated Biphenyls,

“…Using the proposed approach here, already vegetated soils can be targeted for rhizoengineering. This approach, therefore, complements the previous ones requiring establishment of transgenic plants (Oger, 1997;Savka and Farrand, 1997).…”

“…It was thus possible to create a nutritional bias that can be especially successful in identifying microbial populations due to the general nutrient-limiting conditions in the rhizosphere. One of the earliest successes in rhizoengineering was based on favorably partitioning the exotic nutrient, opines, which were produced by the transgenic plants (Oger, 1997;Savka and Farrand, 1997). This led to the improved and competitive growth of the metabolizing strains in comparison with the microbes unable to metabolize opines.…”

Fitness costs restrict niche expansion by generalist niche-constructing pathogens

“…Altogether this work shows that niche expansion may be limited by several mechanisms, thereby explaining the maintenance of multiple specialist strategies in place of a single, generalist one (Futuyama and Moreno, 1988) in A. tumefaciens populations. Because other soil Proteobacteria such as Pseudomonas or Ensifer (Wilson et al, 1995;Oger et al, 1997;Savka and Farrand, 1997;Oger et al, 2004;Mondy et al, 2014) may exploit the opine niches that are constructed by the Agrobacterium pathogens, the question of generalist versus specialist strategy remains to be explored in these niche opportunistic populations of the plant microbiota.…”

Dynamics of the bacterial community structure in the rhizosphere of a maize cultivar

“…Soil pH, structure, oxygen and nutrition levels in the rhizosphere differ from those in the bulk soil (Singh et al, 2004). The unique ecological niche shapes the structure of rhizosphere bacterial community through the interactions of plant species, the chemical nature of root exudates, soil properties, and many other factors (Savka and Farrand, 1997). While some detrimental microbes undermine plant health, mutualistic rhizosphere microbes provide plants with mineral nutrients, phytohormones, and protect the plant against phytopathogens (Mendes et al, 2011;Singh et al, 2004;Vercellino and Gómez, 2013).…”