Compositional variations of active autotrophic bacteria in paddy soils with elevated CO 2 and temperature

Global warming is an increasingly serious ecological problem, we examined how the active autotrophic microbes in paddy soils respond to the elevated CO2 and temperature. Here we employed stable isotope probing (SIP) to label the active bacteria using the soil samples from a fully factorial Simulated Climate Change (SCC) field experiment where soils were exposed to ambient CO2 and temperature, elevated temperature, elevated CO2, and both elevated CO2 and temperature. Around 28.9% of active OTUs belonged to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Nitrosospira taxa was dominant in all soils and 80.4% of carbon-fixing bacteria under elevated temperature were classified as Nitrosomonas nitrosa. While no labeled NOBs were detected when temperature or CO2 were elevated independently, diverse NOBs were detected in the ambient conditions. We found that elevated CO2 and temperature had contrasting effects on microbial community composition, while relatively small changes were observed when CO2 and temperature were elevated simultaneously. Summarily these results suggest that carbon-fixing bacteria can respond positively to elevated CO2 concentrations, but when it’s accompanied with increase in the temperature this positive response could be weakened. Multiple abiotic factors thus need to be considered when predicting how microbial communities will respond to multiple climatic factors.