Sequencing of seven haloarchaeal genomes reveals patterns of genomic flux

We report the sequencing of seven genomes from two haloarchaeal genera, Haloferax and Haloarcula. Ease of cultivation and the existence of well-developed genetic and biochemical tools for several diverse haloarchaeal species make haloarchaea a model group for the study of archaeal biology. The unique physiological properties of these organisms also make them good candidates for novel enzyme discovery for biotechnological applications. Seven genomes were sequenced to ~20×coverage and assembled to an average of 50 contigs (range 5 scaffolds - 168 contigs). Comparisons of protein-coding gene compliments revealed large-scale differences in COG functional group enrichment between these genera. Analysis of genes encoding machinery for DNA metabolism reveals genera-specific expansions of the general transcription factor TATA binding protein as well as a history of extensive duplication and horizontal transfer of the proliferating cell nuclear antigen. Insights gained from this study emphasize the importance of haloarchaea for investigation of archaeal biology.

本研究报道了两个嗜盐古菌（haloarchaeal）属——盐盒菌属（Haloferax）与嗜盐杆菌属（Haloarcula）共7个基因组的测序结果。由于多种不同的嗜盐古菌（haloarchaea）易于培养，且针对这类物种已建立了成熟完善的遗传与生化研究工具，使得嗜盐古菌成为古菌生物学研究的模式类群。此外，这类生物独特的生理特性，使其成为生物技术应用中新型酶类发掘的优质候选对象。本研究对7个基因组进行了测序，测序深度约为20倍，组装后平均获得50个重叠群（contigs），组装结果的跨度为5个支架序列（scaffolds）至168个重叠群。对各基因组的蛋白编码基因组分进行比较分析后发现，这两个属在COG（Cluster of Orthologous Groups）功能类群的富集程度上存在大规模差异。对编码参与DNA代谢的分子机器的基因进行分析后发现，两个属均存在通用转录因子TATA结合蛋白（TATA binding protein）的属特异性扩张，同时增殖细胞核抗原（proliferating cell nuclear antigen，PCNA）也经历了广泛的复制与水平基因转移事件。本研究获得的结果凸显了嗜盐古菌在古菌生物学研究中的重要价值。