The transcriptional response of bacteria to long-term warming and short-term seasonal fluctuations in a terrestrial forest

Community RNA analyses (metatranscriptomics) provides an ideal tool to look at the community dynamics and function of microbes at a given time. In this study, we use methods in metatranscriptomics to look at how bacterial community is responding to long-term warming (26+ years) in Harvard Forest in Petersham, MA. We also look at how these changes are affected by seasonal variations and their interactions thereof. Previous studies in these plots have observed that the carbon stock in the organic horizon (SOM) of the heated plots was reduced by 30% relative to the controls, however, the carbon dioxide fluxes were either similar or higher in the heated plots compared to the control in the recent years in spite of this decrease. Our objective, therefore, was to determine changes in these microbial communities that are associated with accelerated soil carbon loss due to long-term warming. To test this, we sequenced total RNAisolated from soil samples from 2 treatment plots (heated and control), 2soil horizons (mineral and organic) and 2-time points (June and October). The sequencing results indicated that bacteria were dominant across all treatment accounting for 80% of the sequences. Our data suggest that long term warming can result in not only shifts in microbial communities but can also lead to change in the functional characteristics of the community. Such information will enable us to better understand microbial feedbacks in light of current and future global climate changes.