Ecological Implications of Specificity between Plants and Rhizosphere Micro-organisms

Chanway, C. P.; Turkington, Roy; Holl, F. B.

doi:10.1016/s0065-2504(08)60098-7

Cited by 99 publications

(54 citation statements)

References 175 publications

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“…These signals act as chemoattractants at the first stage of the establishment of the Rhizobium-clover symbiosis [14,65], explaining the positive CO 2 effect on bacteria numbers in the RS fraction and the tenfold increase in the RE fraction retrieved in July. In this latter fraction, bacterial counts are mainly assigned to Rhizobium leguminosarum counts because the Trifolium-Rhizobium symbiosis is highly specific [14,65] and because the bacteroids are present in high numbers in nodules. These results are in agreement with those obtained by Schortemeyer et al [57].…”

Section: Impact Of Elevated Co 2 On Heterotrophic Bacteria In the Rhimentioning

confidence: 99%

Influence of an Elevated Atmospheric CO 2 Content on Soil and Rhizosphere Bacterial Communities Beneath Lolium perenne and Trifolium repens under Field Conditions

1999

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The increase in atmospheric CO 2 content alters C 3 plant photosynthetic rate, leading to changes in rhizodeposition and other root activities. This may influence the activity, the biomass, and the structure of soil and rhizosphere microbial communities and therefore the nutrient cycling rates and the plant growth. The present paper focuses on bacterial numbers and on community structure. The rhizospheres of two grassland plants, Lolium perenne (ryegrass) and Trifolium repens (white clover), were divided into three fractions: the bulk soil, the rhizospheric soil, and the rhizoplaneendorhizosphere. The elevated atmospheric CO 2 content increased the most probable numbers of heterotrophic bacteria in the rhizosphere of L. perenne. However, this effect lasted only at the beginning of the vegetation period for T. repens. Community structure was assessed after isolation of DNA, PCR amplification, and construction of cloned 16S rDNA libraries. Amplified ribosomal DNA restriction analysis (ARDRA) and colony hybridization with an oligonucleotide probe designed to detect Pseudomonas spp. showed under elevated atmospheric CO 2 content an increased dominance of pseudomonads in the rhizosphere of L. perenne and a decreased dominance in the rhizosphere of T. repens. This work provides evidence for a CO 2 -induced alteration in the structure of the rhizosphere bacterial populations, suggesting a possible alteration of the plant-growthpromoting-rhizobacterial (PGPR) effect.

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Section: Impact Of Elevated Co 2 On Heterotrophic Bacteria In the Rhimentioning

confidence: 99%

Influence of an Elevated Atmospheric CO 2 Content on Soil and Rhizosphere Bacterial Communities Beneath Lolium perenne and Trifolium repens under Field Conditions

1999

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“…However, soil is a viscous matrix in which bacterial dispersal is limited (Lowther & Patrick 1993;Parco et al 1994), leading to patchy distribution of soil organisms (Turkington & Harper 1979;Chanway et al 1991;Bever et al 1996). In such a structured system, there may be a greater probability than expected by chance that a reproductive cell is genetically identical by descent to bacteroids in the adjacent nodule.…”

Section: Modelmentioning

confidence: 99%

Evolutionary dynamics of rhizopine within spatially structured rhizobium populations

Simms

Bever

1998

Proc. R. Soc. Lond. B

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Symbiosis between legumes and nitrogen-¢xing bacteria is thought to bring mutual bene¢t to each participant. However, it is not known how rhizobia bene¢t from nodulating legume hosts because they ¢x nitrogen only after becoming bacteroids, which are terminally di¡erentiated cells that cannot reproduce. Because undi¡erentiated rhizobia in and around the nodule can reproduce, evolution of symbiotic nitrogen ¢xation may depend upon kin selection. In some hosts, these kin may persist in the nodule as viable, undi¡erentiated bacteria. In other hosts, no viable rhizobia survive to reproduce after nodule senescence. Bacteroids in these hosts may bene¢t their free-living kin by enhancing production of plant root exudates. However, unrelated non-mutualists may also bene¢t from increased plant exudates. Rhizopines, compounds produced by bacteroids in nodules and catabolized only by related free-living rhizobia, may provide a mechanism by which bacteroids can preferentially bene¢t kin. Despite this apparent advantage, rhizopine genotypes are relatively rare. We constructed a mathematical model to examine how mixing within rhizobium populations in£uences the evolution of rhizopine genotypes. Our model predicts that the success of rhizopine genotypes is strongly dependent upon the spatial genetic structure of the bacterial population; rhizopine is more likely to dominate well-mixed populations. Further, for a given level of mixing, we ¢nd that rhizopine evolves under a positive frequency-dependent process in which stochastic accumulation of rhizopine alleles is necessary for rhizopine establishment. This process leads to increased spatial structure in rhizobium populations, and suggests that rhizopine may expand the conditions under which nitrogen ¢xation can evolve via kin selection.

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“…This symbiosis, which primarily involves the exchange of carbohydrates from plants for mineral nutrients from the fungal partners, offers ideal experimental opportunities to study spatial structuring: a single host root can be colonized by several AM fungal species that range in benefit from mutualistic to antagonistic (Hoeksema et al 2010). Although spatial structure has been suggested to play an important role in the maintenance of the mycorrhizal mutualism (Chanway et al 1991;Wilkinson 1998;Bever et al 2009;Hodge et al 2010), observations from the field and lab experiments do not consistently reveal strong structuring of different fungal communities (van Tuinen et al 1998;Jansa et al 2003;Alkan et al 2006), but rather distantly related AM fungi are found to intermingle on a small spatial scale in host roots (Jansa et al 2003). Whether hosts discriminate among intermingled fungal partners, allocating resources preferentially to the best ones, has been the subject of an ongoing debate (Fitter 2006;Kiers and van der Heijden 2006;Bever et al 2009;Helgason and Fitter 2009;Smith et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Spatial Structure and Interspecific Cooperation: Theory and an Empirical Test Using the Mycorrhizal Mutualism

Verbruggen

Mouden

Jansa³

et al. 2012

The American Naturalist

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. abstract: Explaining mutualistic cooperation between species remains a major challenge for evolutionary biology. Why cooperate if defection potentially reaps greater benefits? It is commonly assumed that spatial structure (limited dispersal) aligns the interests of mutualistic partners. But does spatial structure consistently promote cooperation? Here, we formally model the role of spatial structure in maintaining mutualism. We show theoretically that spatial structure can actually disfavor cooperation by limiting the suite of potential partners. The effect of spatial structuring depends on the scale (fine or coarse level) at which hosts reward their partners. We then test our predictions by using molecular methods to track the abundance of competing, closely related, cooperative, and less cooperative arbuscular mycorrhizal (AM) fungal symbionts on host roots over multiple generations. We find that when spatial structure is reduced by mixing soil, the relative success of the more cooperative AM fungal species increases. This challenges previous suggestions that high spatial structuring is critical for stabilizing cooperation in the mycorrhizal mutualism. More generally, our results show, both theoretically and empirically, that contrary to expectations, spatial structuring can select against cooperation. The University of Chicago Press and

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Ecological Implications of Specificity between Plants and Rhizosphere Micro-organisms

Cited by 99 publications

References 175 publications

Influence of an Elevated Atmospheric CO 2 Content on Soil and Rhizosphere Bacterial Communities Beneath Lolium perenne and Trifolium repens under Field Conditions

Influence of an Elevated Atmospheric CO 2 Content on Soil and Rhizosphere Bacterial Communities Beneath Lolium perenne and Trifolium repens under Field Conditions

Evolutionary dynamics of rhizopine within spatially structured rhizobium populations

Spatial Structure and Interspecific Cooperation: Theory and an Empirical Test Using the Mycorrhizal Mutualism

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