The effects of elevated atmospheric carbon dioxide [CO(2)] on microbial communities in arid rhizosphere soils beneath Larrea tridentata were examined. Roots of Larrea were harvested from plots fumigated with elevated or ambient levels of [CO(2)] using Free-Air CO(2) Enrichment (FACE) technology. Twelve bacterial and fungal rRNA gene libraries were constructed, sequenced and categorized into operational taxonomical units (OTUs). There was a significant decrease in OTUs within the Firmicutes (bacteria) in elevated [CO(2)], and increase in Basiomycota (fungi) in rhizosphere soils of plots exposed to ambient [CO(2)]. Phylogenetic analyses indicated that OTUs belonged to a wide range of bacterial and fungal taxa. To further study changes in bacterial communities, Quantitative Polymerase Chain Reaction (QPCR) was used to quantify populations of bacteria in rhizosphere soil. The concentration of total bacteria 16S rDNA was similar in conditions of enriched and ambient [CO(2)]. However, QPCR of Gram-positive microorganisms showed a 43% decrease in the population in elevated [CO(2)]. The decrease in representation of Gram positives and the similar values for total bacterial DNA suggest that the representation of other bacterial taxa was promoted by elevated [CO(2)]. These results indicate that elevated [CO(2)] changes structure and representation of microorganisms associated with roots of desert plants.

中文翻译：

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大气 CO2 升高对莫哈韦沙漠生态系统根际土壤微生物群落的影响

研究了大气二氧化碳升高 [CO(2)] 对 Larrea tridentata 下干旱根际土壤中微生物群落的影响。Larrea 的根是从使用自由空气 CO(2) 富集 (FACE) 技术用升高或环境水平的 [CO(2)] 熏蒸的地块中收获的。12 个细菌和真菌 rRNA 基因文库被构建、测序并分类为操作分类单位 (OTU)。在升高的 [CO(2)] 中厚壁菌门 (细菌) 内的 OTU 显着减少，暴露于环境 [CO(2)] 的地块根际土壤中的担子菌 (真菌) 增加。系统发育分析表明，OTUs 属于广泛的细菌和真菌类群。为了进一步研究细菌群落的变化，定量聚合酶链反应 (QPCR) 用于量化根际土壤中的细菌种群。总细菌 16S rDNA 的浓度在富集和环境 [CO(2)] 的条件下相似。然而，革兰氏阳性微生物的 QPCR 显示在升高 [CO(2)] 中的人口减少了 43%。革兰氏阳性菌代表的减少和细菌总 DNA 的相似值表明其他细菌类群的代表由升高的 [CO(2)] 促进。这些结果表明，升高的 [CO(2)] 改变了与沙漠植物根系相关的微生物的结构和表示形式。革兰氏阳性微生物的 QPCR 显示在升高 [CO(2)] 中的人口减少了 43%。革兰氏阳性菌代表的减少和细菌总 DNA 的相似值表明其他细菌类群的代表由升高的 [CO(2)] 促进。这些结果表明，升高的 [CO(2)] 改变了与沙漠植物根系相关的微生物的结构和表示形式。革兰氏阳性微生物的 QPCR 显示在升高 [CO(2)] 中的人口减少了 43%。革兰氏阳性菌代表的减少和细菌总 DNA 的相似值表明其他细菌类群的代表由升高的 [CO(2)] 促进。这些结果表明，升高的 [CO(2)] 改变了与沙漠植物根系相关的微生物的结构和表示形式。