Phenotypic structure of <i>Pseudomonas</i> populations is altered under elevated pCO<sub>2</sub> in the rhizosphere of perennial grasses
Tarnawski, Sonia Estelle
Date de parution
Soil Biology and Biochemistry, 2006/38/1193-1201
The increasing atmospheric CO<sub>2</sub> content (pCO<sub>2</sub>) is likely to modify the ecosystem functioning including rhizosphere bacteria that are directly dependent on rhizodeposition. This may include alteration of <i>Pseudomonas</i> populations that display phenotypic traits in relation with plant fitness. In the present study, 1228 <i>Pseudomonas</i> strains were isolated from the non-rhizosphere soil, rhizosphere soil and root fractions of perennial grassland systems: <i>Lolium perenne</i> and </i>Molinia coerulea</i>. Both plants were grown under ambient (36 Pa) and elevated (60 Pa) pCO<sub>2</sub> in the Swiss Free Air CO<sub>2</sub> Enrichment (FACE) system. <i>Pseudomonas</i> spp. were tested for their ability to produce auxin, siderophores and hydrogen cyanide, and to dissimilate nitrate. No effect of root proximity and elevated pCO<sub>2</sub> was observed on the proportions of auxin producers. For <i>L. perenne</i> and <i>M. coerulea</i>, siderophore and hydrogen cyanide <i>Pseudomonas</i> producers were stimulated in the root fraction. In contrast lower frequencies of nitrate reducers were observed in the root fraction compared to non-rhizosphere soil. The frequencies of siderophore producers and nitrate dissimilating strains were higher, and those of hydrogen cyanide producers lower, under elevated pCO<sub>2</sub> for <i>L. perenne</i>. This alteration of the phenotypic structure of <i>Pseudomonas</i> guild in the root fraction is discussed in relation with the physico-biochemical modifications of the rhizosphere condition via rhizodeposition and environmental changes occurring under elevated pCO<sub>2</sub>.
Type de publication
Resource Types::text::journal::journal article