"Killing the winner" only? The virome of grassland soils under different land use intensity as the driver for microbial community structure and function (KiWion)

土壤，虽然深入研究其微生物学方面，是落后的病毒生态学研究相比，海洋和淡水系统。事实上，土壤中含有大量的病毒，并且土壤中的病毒与细菌比率（VBR）似乎比水生环境中的变化大得多，经常超过这些1至2个数量级。病毒种群的变化部分是由土壤pH值、水和有机物含量的差异解释的，暗示土地利用差异对病毒多样性和病毒-宿主相互作用产生重大影响。高达68%的土壤细菌可能含有诱导型原噬菌体，有迹象表明，土壤环境的异质性和土壤微生物群落的斑块分布选择溶原性，而不是溶解性繁殖的土壤病毒，其结果是，普遍溶原性的关系增加了噬菌体和原核宿主之间通过转导传递遗传信息的可能性。事实上，分析的病毒宏基因组显示，高达50%由转导的细菌和古细菌基因组成。尽管我们假设土壤中的病毒对宿主动态（杀死赢家假说）和适应（红皇后假说）、生态系统功能和类似于水生系统的生物地球化学过程有显著贡献，但对相互作用的类型和频率了解甚少，经验数据也缺失。我们假设，在强土地利用强度下，转导在土壤恢复力中起着非常重要的作用，因为在这些土壤中，i）土壤微生物的多样性较低，因此生态系统可能对变化的条件更敏感，ii）土壤微生物的活性特别高，这可能会增加转导率，因为病毒在宿主中的复制需要代谢活性细胞。为了研究指导性假设，我们将分析生物多样性勘探站内的150个地块，特别关注不同土地利用强度下的草地生态系统。我们将调查土地利用强度、植被期、特定地点条件和病毒数量之间的关系。我们将进一步描述土壤病毒组的组成以及病毒携带的原核起源的主要功能特征。宿主-病毒相互作用研究和源自原核宿主中CRISPR样结构的感染网络将提供有关群落生态学的信息。最后，我们将分离感染不同草原土壤中常见的主要细菌群（如假单胞菌科）的病毒，以研究它们交叉感染的可能性。

Soils, although intensively studied with respect to their microbiology, are lagging virus ecology research compared to marine and freshwater systems. Indeed, soils harbour high numbers of viruses and virus - to - bacteria ratios (VBR) in soil seem to vary much more than in aquatic environments, frequently exceeding these by 1 to 2 orders of magnitude. Variations in virus populations are partly explained by differences in soil pH, water and organic content, hinting at land use differences posing a significant influence on virus diversity and viral - host interactions. With up to 68% of soil bacteria potentially containing inducible prophages, there is indication that the heterogeneous soil environment and the patchy distribution of soil microbial communities select for lysogenic rather than lytic reproduction in soil viruses, with the consequence, that prevalent lysogenic relationships increase the probability of transferring genetic information between phage and prokaryotic hosts by transduction. And indeed, the viral metagenomes analysed, show that up to 50% consists of transduced bacterial and archaeal genes. Although we assume that viruses in soil significantly contribute to host dynamics (Killing the Winner Hypothesis) and adaptation (Red Queen Hypothesis), ecosystem functioning, and biogeochemical processes similar to aquatic systems, the type and frequency of interactions are poorly understood and empirical data are missing. We hypothesize that transduction plays a very important role for resilience in soils under strong land use intensity, since in these soils i) diversity of soil microbes is lower and thus the ecosystem might be more sensitive to changing conditions and ii) the activity of soil microbes is particularly higher which may increase transduction rates, as the replication of the virus in the host requires metabolically active cells. To investigate the guiding hypothesis we will analyse the 150 plots within the Biodiversity Exploratories with a specific focus on grassland ecosystems under different land use intensity. We will investigate the relation between land use intensity, vegetation period, site specific conditions and the number of viruses. We will further describe the composition of the soil viromes as well as major functional traits of prokaryotic origin carried by viruses. Host - virus interaction studies and infection networks derived from CRISPR like structures in the prokaryotic hosts will provide information on community ecology. Finally, we will isolate viruses infecting dominating bacterial groups common to the different grassland soils (e.g. Pseudomonadaceae) for studying their cross - infection potentials.