The Physiological Characteristics of Specific Microbial Taxa Regulate the Function of Microbial Assemblages
Microorganisms are the drivers of soil organic carbon mineralization, and the activity of soil microorganisms directly affects the turnover rate of soil carbon. Global warming promotes the release of organic carbon from soil, probably because elevated temperature increases the activity of soil microbes, alters the structure of soil microbial assemblages, and thus accelerates the decomposition of soil organic carbon (SOC). However, how to quantify the functional changes of individual microbial taxa and determine the relationship between microbial assemblage functions and soil carbon cycles has been a difficult problem for soil ecologists due to the difficulty in accounting for the functional traits of individual microbial taxa.
DNA-based stable isotope probing (DNA-SIP) can be used to analyse physiological characteristics of microorganisms in the context of complex environments, and can be used to qualitatively indicate which taxa of microorganisms are responsible for a specific material cycling process. In 2000, the first 13C-SIP experiment was developed in Professor J. Colin Murrell's laboratory in the United Kingdom, opening up the research field of coupling stable isotope probing (SIP) with microbial genome research. However, this technique cannot quantify the relative contribution of different microbial taxa to the soil material cycle process.
As an updated tool, quantitative stable isotope probing (qSIP) combines real-time quantitative PCR and high-throughput sequencing techniques to calculate the amount of isotope assimilated by each microbial taxon, and can quantify the role of different microbial taxa in the specific ecological process. In addition, global warming-induced changes in soil microbial physiology and SOC decomposition suggested uncertain relationships.
In view of this, Wang Chao, a research scientist from the Institute of Applied Ecology (IAE), Chinese Academy of Sciences, together with Prof. Ember Morrissey and several other researchers at West Virginia University and Northern Arizona University, conducted a simulated warming experiment and examined the responses of SOC and microbial physiological activity. They sampled soils from tropical, temperate, boreal and Arctic zones, measured carbon mineralization rate and its temperature sensitivity, and quantified soil microbial growth rate and temperature sensitivity using the qSIP technique.
The researchers found that the simulated warming enhanced the mineralization rate of SOC, promoted microbial growth, but reduced the temperature sensitivity of SOC mineralization and the temperature sensitivity of microbial growth. There was a positive correlation between the temperature sensitivity of microbial growth rate and the temperature sensitivity of SOC mineralization, indicating that the response of soil microbial activity to temperature is a key factor regulating soil carbon release. By quantifying each microbial taxon's growth and temperature sensitivity, the researchers found that microbes belonging to the same phylum or class were similar in sensitivity to warming simulation.
This study shows that the physiological characteristics of specific microbial taxa regulate the function of microbial assemblages, which in turn affects material cycle processes in the soil. As the first study that quantified the impact of warming on the growth rate of soil microbes, this study provided important data and technical support for constructing a Global Change Model with Microbial Module.
The study has been published in The ISME Journal, entitled "The temperature sensitivity of soil: microbial biodiversity, growth, and carbon mineralization".
The study was funded by the Chinese Academy of Sciences.
Contact
YUE Qian
Institute of Applied Ecology, Chinese Academy of Sciences
Tel: 86-24-83970324
E-mail: yueqian@iae.ac.cn
