Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax, Sfax, Tunisia.
Appl Environ Microbiol. 2012 Oct;78(20):7429-37. doi: 10.1128/AEM.01793-12. Epub 2012 Aug 17.
The microbial community inhabiting Sfax solar salterns on the east coast of Tunisia has been studied by means of different molecular and culture-dependent tools that have unveiled the presence of novel microbial groups as well as a community structure different from that of other coastal hypersaline environments. We have focused on the study of the viral assemblages of these salterns and their changes along the salinity gradient and over time. Viruses from three ponds (C4, M1, and TS) encompassing salinities from moderately hypersaline to saturated (around 14, 19, and 35%, respectively) were sampled in May and October 2009 and analyzed by transmission electron microscopy (TEM) and pulsed-field gel electrophoresis (PFGE). Additionally, for all three October samples and the May TS sample, viral metagenomic DNA was cloned in fosmids, end sequenced, and analyzed. Viral concentration, as well as virus-to-cell ratios, increased along the salinity gradient, with around 10(10) virus-like particles (VLPs)/ml in close-to-saturation ponds, which represents the highest viral concentration reported so far for aquatic systems. Four distinct morphologies could be observed with TEM (spherical, tailed, spindled, and filamentous) but with various proportions in the different samples. Metagenomic analyses indicated that every pond harbored a distinct viral assemblage whose G+C content could be roughly correlated with that of the active part of the microbial community that may have constituted the putative hosts. As previously reported for hypersaline metaviromes, most sequences did not have matches in the databases, although some were conserved among the Sfax metaviromes. BLASTx, BLASTp, and dinucleotide frequency analyses indicated that (i) factors additional to salinity could be structuring viral communities and (ii) every metavirome had unique gene contents and dinucleotide frequencies. Comparison with hypersaline metaviromes available in the databases indicated that the viral assemblages present in close-to-saturation environments located thousands of kilometers apart presented some common traits among them in spite of their differences regarding the putative hosts. A small core metavirome for close-to-saturation systems was found that contained 7 sequences of around 100 nucleotides (nt) whose function was not hinted at by in silico search results, although it most likely represents properties essential for hyperhalophilic viruses.
突尼斯东部斯法克斯太阳能盐场的微生物群落已通过多种分子和依赖培养的工具进行了研究，这些工具揭示了新型微生物群体的存在以及与其他沿海高盐环境不同的群落结构。我们专注于研究这些盐场的病毒组合及其在盐度梯度和时间上的变化。2009 年 5 月和 10 月，从三个池塘（C4、M1 和 TS）中采集了包含从中等高盐到饱和盐度（分别约为 14%、19%和 35%）的病毒，并通过透射电子显微镜（TEM）和脉冲场凝胶电泳（PFGE）进行了分析。此外，对于所有三个 10 月的样本和 5 月的 TS 样本，都用 fosmid 克隆了病毒宏基因组 DNA，末端测序并进行了分析。病毒浓度以及病毒与细胞的比例沿盐度梯度增加，在接近饱和的池塘中，病毒样颗粒（VLPs）的浓度约为 10(10)个/ml，这是迄今为止报道的水生系统中最高的病毒浓度。通过 TEM 可以观察到四种不同的形态（球形、长尾、纺锤形和丝状），但在不同的样本中比例不同。宏基因组分析表明，每个池塘都有一个独特的病毒组合，其 GC 含量与可能构成假定宿主的微生物群落的活性部分大致相关。正如以前报道的高盐代谢组学一样，大多数序列在数据库中没有匹配，但有些序列在斯法克斯代谢组学中是保守的。BLASTx、BLASTp 和二核苷酸频率分析表明，（i）除盐度以外的因素可能会影响病毒群落的结构，（ii）每个代谢组都有独特的基因组成和二核苷酸频率。与数据库中可用的高盐代谢组学的比较表明，尽管它们的假定宿主不同，但位于数千公里之外的接近饱和环境中的病毒组合之间存在一些共同特征。发现了一个接近饱和系统的小核心代谢组，其中包含 7 个约 100 个核苷酸（nt）的序列，通过计算机搜索结果没有暗示其功能，尽管它很可能代表了嗜盐病毒的基本特性。
