%0 Journal Article
%T Glucose triggers strong taxon©\specific responses in microbial growth and activity: insights from DNA and RNA qSIP
%A Bruce A. Hungate
%A Egbert Schwartz
%A Katerina Papp
%J Ecology - Wiley Online Library
%D 2019
%R https://doi.org/10.1002/ecy.2887
%X Growth of soil microorganisms is often described as carbon limited, and adding labile carbon to soil often results in a transient and large increase in respiration. In contrast, soil microbial biomass changes little, suggesting that growth and respiration are decoupled in response to a carbon pulse. Alternatively, measuring bulk responses of the entire community (total respiration and biomass) could mask ecologically important variation among taxa in response to the added carbon. Here, we assessed taxon©\specific variation in cellular growth (measured as DNA synthesis) and metabolic activity (measured as rRNA synthesis) following glucose addition to soil using quantitative stable isotope probing with H218O. We found that glucose addition altered rates of DNA and rRNA synthesis, but the effects were strongly taxon specific: glucose stimulated growth and rRNA transcription for some taxa, and suppressed these for others. These contrasting taxon©\specific responses could explain the small and transient changes in total soil microbial biomass. Responses to glucose were not well predicted by a priori assignments of taxa into copiotrophic or oligotrophic categories. Across all taxa, rates of DNA and rRNA synthesis changed in parallel, indicating that growth and activity were coupled, and the degree of coupling was unaffected by glucose addition. This pattern argues against the idea that labile carbon addition causes a large reduction in metabolic growth efficiency; rather, the large pulse of respiration observed with labile substrate addition is more likely to be the result of rapid turnover of microbial biomass, possibly due to trophic interactions. Our results support a strong connection between rRNA synthesis and bacterial growth, and indicate that taxon©\specific responses among soil bacteria can buffer responses at the scale of the whole community. Growth of soil microorganisms is generally limited by carbon availability (Joergensen and Scheu 1999, Ilstedt and Singh 2005, Demoling et al. 2007, Hill et al. 2008), even though soils can be carbon©\rich environments. For example, glucose and other root exudates are periodically released into the rhizosphere (Rangel©\Castro et al. 2005). These are natural carbon inputs to soil that can alleviate carbon limitation, boosting microbial activity and growth (Kuzyakov and Blagodatskaya 2015). These substrate inputs can also affect the fate of native soil organic matter, referred to as the priming effect (Bingeman et al. 1953, De Nobili et al. 2001, Blagodatskaya et al. 2007), and they can also induce a shift in microbial
%U https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2887