Identification of keystone prokaryotic food web members and links in belowground carbon turnover - SP MicLink

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The MicLink project within FOR aims to elaborate a precise understanding of trophic connectivities and carbon flow amongst bacterial members of a belowground food web. In the first phase of funding, we have generated a unique matrix of bacterial community structure and distribution at our joint experimental field site, partly based on pyrotag sequencing, and identified several primary plant-dependent bacterial food web constituents by rRNA-SIP. In the next phase, we want to address an emerging hypothesis that while protozoan predation may well be a relevant control of Bacteria in plant-associated soil, intra-bacterial predation e.g. by Myxobacteria may be of overlooked importance especially in bulk soil. Furthermore, we have preliminarily identified specific subsets of rhizosphere Bacteria that seem to be selectively mobilised to deeper zones upon groundwater recharge events. This could represent an organismic and trophic connectivity between top soil and deeper mineral soils that is still poorly understood. Now, we plan to quantify microbial mobilisation rates and fluxes using amended 13C-labelled biomass and single-cell recovery in seepage water using NanoSIMS. Moreover, we will continue our field and laboratory contribution to joint experiments, focussing now on herbivore vs. detrital food chains, and on quantitative fluxes in selected food web connectivities. The provided qualitative and quantitative data on keystone microbial food web connectivities will be an essential prerequisite for a realistic modelling of carbon flow in belowground food webs.