Frigaard Niels-Ulrik, Martinez Asuncion, Mincer Tracy J, DeLong Edward F
Department of Civil and Environmental Engineering and Division of Biological Engineering, Massachusetts Institute of Technology, Building 48, 15 Vassar Street, Cambridge, Massachusetts 02139, USA.
Nature. 2006 Feb 16;439(7078):847-50. doi: 10.1038/nature04435.
Planktonic Bacteria, Archaea and Eukarya reside and compete in the ocean's photic zone under the pervasive influence of light. Bacteria in this environment were recently shown to contain photoproteins called proteorhodopsins, thought to contribute to cellular energy metabolism by catalysing light-driven proton translocation across the cell membrane. So far, proteorhodopsin genes have been well documented only in proteobacteria and a few other bacterial groups. Here we report the presence and distribution of proteorhodopsin genes in Archaea affiliated with the order Thermoplasmatales, in the ocean's upper water column. The genomic context and phylogenetic relationships of the archaeal and proteobacterial proteorhodopsins indicate its probable lateral transfer between planktonic Bacteria and Archaea. About 10% of the euryarchaeotes in the photic zone contained the proteorhodopsin gene adjacent to their small-subunit ribosomal RNA. The archaeal proteorhodopsins were also found in other genomic regions, in the same or in different microbial lineages. Although euryarchaeotes were distributed throughout the water column, their proteorhodopsins were found only in the photic zone. The cosmopolitan phylogenetic distribution of proteorhodopsins reflects their significant light-dependent fitness contributions, which drive the photoprotein's lateral acquisition and retention, but constrain its dispersal to the photic zone.
浮游细菌、古菌和真核生物在海洋光合层中生存并竞争，受到光的普遍影响。最近发现，这种环境中的细菌含有一种名为视紫质的光蛋白，据认为它通过催化光驱动的质子跨细胞膜转运，对细胞能量代谢有贡献。到目前为止，视紫质基因仅在变形菌和其他一些细菌类群中有详细记录。在此，我们报告了海洋上层水柱中与嗜热栖热菌目相关的古菌中视紫质基因的存在和分布情况。古菌和变形菌视紫质的基因组背景和系统发育关系表明，它可能在浮游细菌和古菌之间横向转移。光合层中约10%的广古菌在其小亚基核糖体RNA附近含有视紫质基因。在其他基因组区域中，在相同或不同的微生物谱系中也发现了古菌视紫质。虽然广古菌分布在整个水柱中，但它们的视紫质仅在光合层中被发现。视紫质在全球范围的系统发育分布反映了它们对光依赖适应性的显著贡献，这推动了光蛋白的横向获取和保留，但限制了其扩散到光合层。
