Abstract
Soil community responses to increased atmospheric CO(2) concentrations are expected to occur mostly through interactions with changing vegetation patterns and plant physiology. To gain insight into the effects of elevated atmospheric CO(2) on the composition and functioning of microbial communities in the rhizosphere, Carex arenaria (a non-mycorrhizal plant species) and Festuca rubra (a mycorrhizal plant species) were grown under defined atmospheric conditions with either ambient (350 p.p.m.) or elevated (700 p.p.m.) CO(2) concentrations. PCR-DGGE (PCR-denaturing gradient gel electrophoresis) and quantitative-PCR were carried out to analyze, respectively, the structure and abundance of the communities of actinomycetes, Fusarium spp., Trichoderma spp., Pseudomonas spp., Burkholderia spp. and Bacillus spp. Responses of specific functional groups, such as phloroglucinol, phenazine and pyrrolnitrin producers, were also examined by quantitative-PCR, and HPLC (high performance liquid chromatography) was employed to assess changes in exuded sugars in the rhizosphere. Multivariate analysis of group-specific community profiles showed disparate responses to elevated CO(2) for the different bacterial and fungal groups examined, and these responses were dependent on plant type and soil nutrient availability. Within the bacterial community, the genera Burkholderia and Pseudomonas, typically known as successful rhizosphere colonizers, were significantly influenced by elevated CO(2), whereas the genus Bacillus and actinomycetes, typically more dominant in bulk soil, were not. Total sugar concentrations in the rhizosphere also increased in both plants in response to elevated CO(2). The abundances of phloroglucinol-, phenazine- and pyrrolnitrin-producing bacterial communities were also influenced by elevated CO(2), as was the abundance of the fungal genera Fusarium and Trichoderma.
Highlights
Since the advent of the industrial revolution, the concentration of atmospheric CO2 in the Earth’s atmosphere has increased by 31%, and it is expected to rise at an annual rate of 0. 5% (Alley et al, 2007)
Distancebased redundancy analysis of community profiles showed that increased atmospheric CO2 exerted differential influences on the specific bacterial groups in the rhizosphere samples associated with C. arenaria and F. rubra
Concluding remarks under different atmospheric CO2 conditions, and our previous observation that the mycorrhizal plant (F. rubra) exerted greater influence on bacterial and fungal communities is consistent with this assertion (Drigo et al, 2007)
Summary
Since the advent of the industrial revolution, the concentration of atmospheric CO2 in the Earth’s atmosphere has increased by 31%, and it is expected to rise at an annual rate of 0. 5% (Alley et al, 2007). C flux can be mediated through DNA isolation and PCR-DGGE analyses arbuscular mycorrhizal fungi (AMF) These symbio- Plant production, incubation conditions at ambient tic fungi, which infect the majority of land plants and elevated CO2 and harvesting procedures are (Smith and Read, 1997), have been shown to explained in detail in Drigo et al (2007). Influence C flow in response to elevated CO2, week-old sterilized seedlings of F. rubra (a mycorthereby affecting soil microbial-community abun- rhizal plant) and C. arenaria (a non-mycorrhizal dance and structure (Jones et al, 1998; Drigo et al, plant) were planted in a coastal-dune soil A total of 240 pots spheric CO2 concentrations have either examined (750 cm3) were filled with 1 kg of soil and adjusted total microbial-community patterns
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