Linking carbon and nitrogen availability to microbial phosphorous turnover in different forest soils

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The development of phosphorous (P) versus nitrogen (N) and carbon (C) contents in soil is reverse. While P concentrations might be high in young ecosystems, given that the bedrock contains P, N and C accumulates over time by initial N2 and CO2 fixation or deposition and later by the turnover of biomass. In contrast to N and C the overall amount of P in soils is stable, if no biomass is removed or no fertilizers are added. Consequently, the addition of nutrients might alter the dynamic of the whole system by increasing or decreasing the microbial activity, changing the microbial community composition or both in combination. Therefore, it is our aim (i) to follow changes in the activity and composition of microbial communities driving P turnover under natural conditions and after altered P, N, C contents and water availability in soil, (ii) to study the interlink between microbial communities driving P turnover to those catalysing major steps in N and C transformation and (iii) to follow spatial distributions of microbes being involved in P turnover and uptake. We hypothesize that the addition of P will not induce significant changes in the P transformation processes, while the addition of N or reduction of C will dramatically alter P transformation processes. To reach the described aims metagenomic and metatranscriptomic approaches will be combined with quantitative PCR and amplicon sequencing to compare the structure, function and abundance of the active and present microbial communities. Therefore, primers will be used for alkaline phosphatase (phoD), phosphonatase (phnX), phytase (HAP) (appA), Pit-Transporter (pitA), Pst-Transporter (pstS) and the quinoprotein glucose dehydrogenase (gcd), which we developed during the 1st phase of the SPP. To follow changes in the active community samples will be taken several times per day to take daily fluctuations of root exudation, light, temperature, humidity etc. into account. Moreover, the presence of alkaline and acidic phosphatases in the rhizosphere will be connected to the presence of different bacteria by applying soil zymography and fluorescence-in situ-hybridization (FISH). By combining those different methods, we hope to better understand the interplay of microbial P, N and C turnover.