Impact of salinity changes on viral production during the paleoenvironmental history of Baltic Sea sediments

波罗的海深层地下沉积物代表了这一陆内盆地的古环境档案，该盆地在过去经历了湖沼、咸水和海洋条件的变化。IODP Exp.347一直在调查这些环境变化对底栖微生物群落的影响。由于病毒控制微生物种群并调节受感染细胞裂解导致的碳周转，它们对微生物和生物地球化学过程产生重大影响。在第一个资助期，我们已经开始分析病毒及其宿主细菌，作为深层生物圈的众多活跃组成部分。为了快速准确地对培养基中的病毒进行计数，我们开发了一种流式细胞术的方法，该方法现在可以用于大量样品，这些样品将适合于对沉积物中的病毒进行计数。从我们的培养实验中，我们获得了36个菌株，其中一些将被有效地描述为新种甚至新属。生理分析表明，它们的耐盐性存在很大差异。在这些分离株中已经鉴定出不同的病毒，这些病毒要么是由抗生素丝裂霉素诱导的，要么是在细菌生长过程中大量产生的。在拟议的项目中，我们将建立我们分离株的噬菌体基因组数据库，这可能会揭示对深层生物圈中的持久性非常重要的病毒特征，并缓解在深层生物圈中识别特定噬菌体的问题，例如，元基因组或单细胞基因组。此外，我们目前关于渗透休克作为病毒产生诱导剂的研究将从纯培养扩展到环境样本。分析细胞裂解过程中的微生物群落结构和有机碳组成，有助于理解病毒在波罗的海古环境历史中的作用。

Deep subsurface sediments of the Baltic Sea represent a paleoenvironmental archive of this intra-continental basin which has undergone alterations between limnic, brackish and marine conditions in the past. The aim of IODP Exp. 347 has been to investigate the impact of these environmental changes on benthic microbial communities. As viruses control microbial populations and mediate carbon turnover due to lysis of infected cells, they have a major impact on microbial and biogeochemical processes. In the first funding period, we have started to analyze viruses and their host bacteria as numerous and active components of the deep biosphere. For fast and accurate counting of viruses in culture media, we have developed a protocol for flow cytometry that can now be used for a large number of samples which will be adapted for counting viruses in sediments. From our cultivation experiments, we have obtained 36 isolates; some of them will be validly described as new species or even genera. Physiological analysis revealed considerable differences in their salinity tolerance. Different viruses have been identified in the isolates, which are either induced by the antibiotic mitomycin or produced at high numbers during growth of the bacteria. In the proposed project, we will establish a database of phage genomes from our isolates which will possibly reveal viral features important for the persistence in the deep biosphere and alleviate the identification of specific phages in e.g. metagenomes or single-cell genomes from the deep biosphere. Furthermore, our current studies on osmotic shock as an inducer for virus production will be extended from pure cultures to environmental samples. Analyzing microbial community structures and organic carbon composition during cell lysis and subsequent uptake of cell material by opportunistic bacteria will help to understand the role of viruses during the paleoenvironmental history of the Baltic Sea.