Microbial phosphorus cycling in acquiring and recycling ecosystems (Micro P Cycling)

磷在各种尺度上循环：生态系统水平、群落水平、生物体水平。在这里，我们试图区分微生物的P循环模式在社区和生物体水平。我们假设维持过程维持生物体水平的循环。相比之下，群落水平的P循环的特征在于i）微生物死亡和P释放，其次是ii）微生物生长和P吸收。因此，我们面临的根本挑战是解开两种模式的微生物营养循环系统在稳态下。我们假设1）死亡/生长模式下的P循环比维持模式下快得多; 2）高P土壤（获取生态系统）中的微生物P循环比维持模式下的低P土壤（循环生态系统）更密集，并由死亡/生长模式主导，因为P限制需要更有效的内部资源利用。我们还假设3）高的C和N可用性主要以死亡/生长模式刺激微生物P循环，4）与真菌相比，细菌中的P循环更快。生物体水平和群落水平的P循环将通过五种独立的途径来解开：1）33 P、14 C和13 C掺入磷脂中（通过Prep-UHPLC分析和收集），2）33 P和14 C掺入DNA，3）ATP含量和腺苷酸能荷，（4）磷肥对CO_2释放的影响;（5）磷肥对土壤热释放的影响。为了将33 P/14 C/13 C掺入单个微生物组的磷脂中，并因此鉴定微生物的关键参与者，将进一步开发和标准化新的制备方法。微生物磷循环的主要假设将测试所有五种方法在微观和田间实验中的土壤对比总磷水平（卢斯与坏Brückenau）和磷形态（Mittelfels与Achenpass）。33 P和14 C的掺入和释放的微生物组，区分磷脂的动力学，将允许在回收和收购ecosystems.Microbial P循环下的维护和死亡/生长模式下的微生物P循环的评估，有效C的影响下，释放在山毛榉根际生长在土壤中的根均匀与异质P分布，将在合作的微观和现场实验进行测试。此外，还将在田间试验中分析施磷和施氮对土壤微生物磷循环的影响。这些研究，基于上述五种方法，将提供新的方法解开P和营养循环之间的社区和生物体水平，以确定比例的贡献维护与死亡/生长微生物循环模式在收购和回收生态系统。

Phosphorus (P) is cycled on various scales of all magnitudes: ecosystem level, community level, organism level. Here, we seek to distinguish between microbial P cycling modes at the community and organism levels. We assume that maintenance processes sustain organism level cycling. In contrast, community level P cycling is characterized by i) microbial death and P release, following by ii) microbial growth and P uptake. Thus, we face the fundamental challenge of disentangling the two modes of microbial nutrient cycling in systems under steady state. We hypothesize that 1) P cycling in Death/Growth mode is much faster compared to that in Maintenance mode, and 2) Microbial P cycling in high P soil (acquiring ecosystems) is more intensive and dominated by Death/Growth mode compared to low P soil (recycling ecosystems) dominated by Maintenance mode, as P limitations require more efficient internal resource use. We also hypothesize that 3) high C and N availability stimulate microbial P cycling mainly in Death/Growth mode, which is 4) faster in bacteria compared to fungi.The organism level and community level P cycling will be disentangled by five independent approaches: 1) 33P, 14C and 13C incorporation into phospholipids (analyzed and collected by Prep-UHPLC), 2) 33P and 14C incorporation into DNA, 3) ATP content and Adenylate Energy Charge, 4) effect of P fertilization on CO2 release and 5) on heat release (calorimetry) from soil. For the 33P/14C/13C incorporation into phospholipids of individual microbial groups, and consequently identification of microbial key players, a new preparative approach will be further developed and standardized. The main hypotheses on microbial P cycling will be tested by all five approaches in microcosms and field experiments in soils with contrasting total P levels (Luess vs. Bad Brückenau) and P speciation (Mittelfels vs. Achenpass). Dynamics of 33P and 14C incorporation into and release from microbial groups, distinguished by phospholipids, will allow assessment of microbial P cycling under Maintenance and Death/Growth modes in recycling and acquiring ecosystems.Microbial P cycling under the effects of available C, released in beech rhizosphere by roots grown in soil with homogenous vs. heterogeneous P distribution, will be tested in collaborative microcosm and field experiments. In addition the effects of P and N addition on microbial P cycling will be analyzed in a factorial N × P application field experiment. These studies, based on the five approaches outlined above, will provide novel methods of disentangling P and nutrient cycling between community and organism levels to determine the proportional contribution of Maintenance vs. Death/Growth microbial cycling modes in acquiring and recycling ecosystems.