Palesse S, Colombet J, Pradeep Ram A S, Sime-Ngando T
Laboratoire Microorganismes: Génome et Environnement, UMR CNRS 6023, Clermont Université, Université Blaise Pascal, BP 80026, 63171, Aubière Cedex, France.
Microb Ecol. 2014 Nov;68(4):740-50. doi: 10.1007/s00248-014-0441-2. Epub 2014 Jun 10.
In aquatic ecosystems, fluctuations in environmental conditions and prokaryotic host physiological states can strongly affect the dynamics of viral life strategies. The influence of prokaryote physiology and environmental factors on viral replication cycles (lytic and lysogeny) was investigated from April to September 2011 at three different strata (epi, meta, and hypolimnion) in the mixolimnion of deep volcanic temperate freshwater Lake Pavin (France). Overall, the euphotic region (epi and metalimnion) was more dynamic and showed significant variation in microbial standing stocks, prokaryotic physiological state, and viral life strategies compared to the aphotic hypolimnion which was stable within sampled months. The prokaryotic host physiology as inferred from the nucleic acid content of prokaryotic cells (high or low nucleic acid) was strongly regulated by the chlorophyll concentration. The predominance of the high nucleic acid (HNA) prokaryotes (cells) over low nucleic acid (LNA) prokaryotes (cells) in the spring (HNA/LNA = 1.2) and vice versa in the summer period (HNA/LNA = 0.4) suggest that the natural prokaryotic communities underwent major shifts in their physiological states during investigated time period. The increase in the percentage of inducible lysogenic prokaryotes in the summer period was associated with the switch in the dominance of LNA over HNA cells, which coincided with the periods of strong resource (nutrient) limitation. This supports the idea that lysogeny represents a maintenance strategy for viruses in unproductive or harsh nutrient/host conditions. A negative correlation of percentage of lysogenic prokaryotes with HNA cell abundance and chlorophyll suggest that lysogenic cycle is closely related to prokaryotic cells which are stressed or starved due to unavailability of resources for its growth and activity. Our results provide support to previous findings that changes in prokaryote physiology are critical for the promotion and establishment of lysogeny in aquatic ecosystems, which are prone to constant environmental fluctuations.
在水生生态系统中，环境条件的波动和原核宿主的生理状态会强烈影响病毒生命策略的动态变化。2011年4月至9月期间，在法国深火山温带淡水湖帕万湖的混合湖层的三个不同水层（表层、温跃层和湖下层），研究了原核生物生理学和环境因素对病毒复制周期（裂解和溶原）的影响。总体而言，与无光的湖下层相比，真光层（表层和温跃层）更具动态性，并且在微生物存量、原核生物生理状态和病毒生命策略方面表现出显著差异，湖下层在采样月份内较为稳定。从原核细胞的核酸含量（高核酸或低核酸）推断出的原核宿主生理学受到叶绿素浓度的强烈调节。春季高核酸（HNA）原核生物（细胞）占低核酸（LNA）原核生物（细胞）的优势（HNA/LNA = 1.2），而夏季则相反（HNA/LNA = 0.4），这表明在研究期间，天然原核生物群落的生理状态发生了重大变化。夏季可诱导溶原性原核生物百分比的增加与LNA细胞对HNA细胞优势地位的转变有关，这与强烈的资源（营养）限制时期相吻合。这支持了溶原性代表病毒在非生产性或恶劣营养/宿主条件下的一种维持策略的观点。溶原性原核生物百分比与HNA细胞丰度和叶绿素呈负相关，这表明溶原周期与因生长和活动资源不可用而受到压力或饥饿的原核细胞密切相关。我们的结果为先前的研究结果提供了支持，即原核生物生理学的变化对于水生生态系统中溶原性的促进和建立至关重要，而水生生态系统容易受到持续的环境波动影响。
