Rhizosphere bacteria degrade a key root exudate metabolite critical for pathogen germination and root infection

Glutamine (Gln), present within potato root exudates, stimulates germination of resting spores and chemotactic attraction of zoospores of the plasmodiophorid pathogen, Spongospora subterranea. We hypothesized that rhizosphere bacteria could alter the rhizosphere metabolome by diminishing the occurrence of Gln with the eventual aim of reducing pathogen activation, attraction and infection. This study aimed to isolate and characterize bacteria capable of substantially degrading Gln within the potato rhizosphere.

Eleven bacteria were isolated from potato rhizosphere samples using Gln as a sole carbon source. Of these, Pantoea sp. (RR15) and Rhodococcus sp. (RR09) showed superior Gln degradation potential. Both isolates established within the potato rhizosphere and reduced Gln concentrations in situ. Further analysis of the rhizosphere metabolome showed significant treatment effects for a range of other organic compounds, including some known to stimulate or inhibit Spongospora subterranea germination and/or taxis.

We demonstrate that establishing selected bacteria in the rhizosphere of potatoes can successfully modify the root rhizosphere metabolome.