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

土壤中磷(P)与氮(N)、碳(C)含量的变化趋势相反。虽然在年轻的生态系统中磷的浓度可能很高，但考虑到基岩中含有磷，氮和碳会随着时间的推移通过最初的氮气和二氧化碳的固定或沉积以及后来的生物质周转积累起来。与N和C相反，如果不去除生物量或不添加化肥，土壤中P的总量是稳定的。因此，营养物质的添加可能会通过增加或降低微生物活性、改变微生物群落组成或两者结合来改变整个系统的动态。因此，我们的目标是(I)跟踪在自然条件下和土壤中P、N、C含量和水分有效性改变后驱动P周转的微生物群落的活动和组成的变化，(Ii)研究驱动P周转的微生物群落与催化N和C转化的主要步骤之间的联系，以及(Iii)跟踪参与P周转和吸收的微生物的空间分布。我们假设P的添加不会引起P转化过程的显著变化，而N的添加或C的减少将显著改变P的转化过程。为了达到所描述的目标，将结合定量聚合酶链式反应和扩增序列分析来比较活跃微生物群落和现有微生物群落的结构、功能和丰度。因此，针对碱性磷酸酶(PHOD)、磷酸酶(PHNX)、植酸酶(HAP)(APPA)、果核转运蛋白(PITA)、PST转运蛋白(PSTS)和藜麦蛋白葡萄糖脱氢酶(GCD)的扩增产物进行了研究。为了跟踪活跃群落的变化，每天将采集几次样本，以考虑根系分泌物、光照、温度、湿度等的每日波动。此外，通过应用土壤酶谱和荧光原位杂交(FISH)，根际中碱性和酸性磷酸酶的存在将与不同细菌的存在联系起来。通过结合这些不同的方法，我们希望更好地了解微生物P、N和C周转的相互作用。

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.