Pedosphere 32(3): 402--413, 2022
ISSN 1002-0160/CN 32-1315/P
©2022 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Heterotrophy-coordinated diazotrophy is associated with significant changes of rare taxa in soil microbiome
Wei GAO1,2, Lianfeng WANG3, Zhongjun JIA1
1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008(China)
2University of Chinese Academy of Sciences, Beijing 100049(China)
3College of Environmental and Chemical Engineering, Dalian Jiaotong University, Dalian 116028(China)
      Soil heterotrophic respiration during decomposition of carbon (C)-rich organic matter plays a vital role in sustaining soil fertility. However, it remains poorly understood whether dinitrogen (N2) fixation occurs in support of soil heterotrophic respiration. In this study, 15N2-tracing indicated that strong N2 fixation occurred during heterotrophic respiration of carbon-rich glucose. Soil organic 15N increased from 0.37 atom% to 2.50 atom% under aerobic conditions and to 4.23 atom% under anaerobic conditions, while the concomitant CO2 flux increased by 12.0-fold under aerobic conditions and 5.18-fold under anaerobic conditions. Soil N2 fixation was completely absent in soils replete with inorganic N, although soil N bioavailability did not alter soil respiration. High-throughput sequencing of the 16S rRNA gene further indicated that: i) under aerobic conditions, only 15.2% of soil microbiome responded positively to glucose addition, and these responses were significantly associated with soil respiration and N2 fixation and ii) under anaerobic conditions, the percentage of responses was even lower at 5.70%. Intriguingly, more than 95% of these responses were originally rare with < 0.5% relative abundance in background soils, including typical N2-fixing heterotrophs such as Azotobacter and Clostridium and well-recognized non-N2-fixing heterotrophs such as Sporosarcina, Agromyces, and Sedimentibacter. These results suggest that only a small portion of the soil microbiome could respond quickly to the amendment of readily accessible organic C in a fluvo-aquic soil and highlighted that rare phylotypes might have played more important roles than previously appreciated in catalyzing soil C and nitrogen turnovers. Our study indicates that N2 fixation could be closely associated with microbial turnover of soil organic C when available in excess.
Key Words:  rare phylotypes,diazotrophs,heterotrophic respiration,N2 fixation,15N2-tracing
Citation: Gao W, Wang L F, Jia Z J. 2022. Heterotrophy-coordinated diazotrophy is associated with significant changes of rare taxa in soil microbiome. Pedosphere. 32(3): 402–413.
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