Plant root‐associated microbial communities profoundly affect plant nutrition and productivity. Although elevated atmospheric CO2 and warming affect above‐ and belowground plant processes, it remains unclear how root‐associated microbial communities respond to elevated CO2 and warming. In this study, an open‐air field experiment was conducted to assay the interactive effects of elevated CO2 (500 ppm) and warming (+2°C) on the root‐associated microbiota and soil enzyme activities in a rice–wheat rotation ecosystem. The results revealed that elevated CO2 significantly increased rhizosphere soil organic carbon (SOC) and total nitrogen contents. In addition, glucosidase, β‐xylosidase, and phosphatase activities significantly increased. The richness and Shannon diversity indices were significantly higher in rhizosphere soil than in root endosphere. Elevated CO2 and warming significantly impacted the rhizosphere soil microbiota and altered their composition by changing the relative abundance of some specific groups. Soil pH, SOC, and available potassium content significantly altered the dominant bacterial phyla in the rhizosphere. SOC affected root endophytic bacterial phyla. Bacterial and fungal genera were significantly correlated with soil variables in the rhizosphere than in the root endosphere. These results indicate that microbial communities in the rhizosphere are more sensitive to elevated CO2 and warming than those in the root endosphere.
Background: Plant root-associated microbial communities profoundly affect plant nutrition and productivity. Although elevated atmospheric CO2 and warming have been suggested to affect above- and belowground plant processes, it remains unclear how root-associated microbial communities respond to elevated CO2 and warming, particularly in agroecosystems. Result: Here, an open-air field experiment was conducted to assay the interactive effects of elevated CO2 (500 ppm) and warming (+2℃) on the root-associated microbiomes and soil enzyme activities in a rice-wheat rotation ecosystem. The results revealed a significant increase in rhizosphere soil organic carbon (SOC) and total nitrogen contents from elevated CO2. In addition, glucosidase, β-xylosidase, and phosphatase activities increased significantly. The rhizosphere soils of rice and wheat had significantly higher richness and Shannon diversity indices than the root endosphere. Besides, the bacterial and fungal compositions were significantly altered between the two compartments. Elevated CO2 and warming had more impact on the rhizosphere soil microbiomes and altered their composition by changing the relative abundance of some particular groups. Soil pH, SOC, and available potassium significantly altered the dominant bacterial phyla in the rhizosphere. In contrast, the SOC affected the root endophytic bacterial phyla. Moreover, more bacterial and fungal genera were significantly correlated with soil variables in the rhizosphere than in the root endosphere. Elevated CO2 had significant effects on the numbers of bacterial genera, including Burkholderia, Rhizobium, Pantoea, Gemmatimonas, Dongia, Defluviicoccus, Anaeromyxobacter, and Povalibacter, that significantly correlated with soil variables. Conclusion: These results indicate that the microbial communities in the rhizosphere of rice and wheat are more sensitive to elevated CO2 and warming than the root endophytic microbiomes. Moreover, the dissimilarity of root-associated bacteria is greater than that of the fungal community in the root endosphere.
A Gram-stain-negative, non-spore-forming and rod-shaped bacterium, designated strain NS-102T, was isolated from herbicide-contaminated soil sampled in Nanjing, PR China, and its taxonomic status was investigated by a polyphasic approach. Cell growth of strain NS-102T occurred at 16–42 °C (optimum, 30 °C), at pH 5.0–8.0 (optimum, pH 6.0) and in the presence of 0–3.5 % (w/v) NaCl (optimum, without addition of NaCl). The 16S rRNA gene sequence of strain NS-102T shows high similarity to that of Agriterribacter humi YJ03T (96.9 % similarity), followed by Terrimonas terrae T16R-129T (93.8 %) and Terrimonas pekingensis QHT (93.6 %). Average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between the draft genomes of strain NS-102T and A. humi YJ03T were 72.5, 69.4 and 18.6%, respectively. The only respiratory quinone was MK-7, and phosphatidylethanolamine and unidentified lipids were the major polar lipids. The major cellular fatty acids of strain NS-102T contained high amounts of iso-C15 : 0 (24.6 %), iso-C17 : 03-OH (24.1 %), iso-C15 : 0 G (16.6 %) and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) (15.6 %). The G+C content of the total DNA was determined to be 40.0 mol%. The morphological, physiological, chemotaxonomic and phylogenetic analyses clearly distinguished this strain from its closest phylogenetic neighbours. Thus, strain NS-102T represents a novel species of the genus Agriterribacter , for which the name Agriterribacter soli sp. nov. is proposed. The type strain is NS-102T (=CCTCC AB 2017249T=KCTC 62322T).
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