Giovannoni Stephen J, Bibbs Lisa, Cho Jang-Cheon, Stapels Martha D, Desiderio Russell, Vergin Kevin L, Rappé Michael S, Laney Samuel, Wilhelm Lawrence J, Tripp H James, Mathur Eric J, Barofsky Douglas F
Department of Microbiology.
Nature. 2005 Nov 3;438(7064):82-5. doi: 10.1038/nature04032.
Proteorhodopsins are light-dependent proton pumps that are predicted to have an important role in the ecology of the oceans by supplying energy for microbial metabolism. Proteorhodopsin genes were first discovered through the cloning and sequencing of large genomic DNA fragments from seawater. They were later shown to be widely distributed, phylogenetically diverse, and active in the oceans. Proteorhodopsin genes have not been found in cultured bacteria, and on the basis of environmental sequence data, it has not yet been possible to reconstruct the genomes of uncultured bacterial strains that have proteorhodopsin genes. Although the metabolic effect of proteorhodopsins is uncertain, they are thought to function in cells for which the primary mode of metabolism is the heterotrophic assimilation of dissolved organic carbon. Here we report that SAR11 strain HTCC1062 ('Pelagibacter ubique'), the first cultivated member of the extraordinarily abundant SAR11 clade, expresses a proteorhodopsin gene when cultured in autoclaved seawater and in its natural environment, the ocean. The Pelagibacter proteorhodopsin functions as a light-dependent proton pump. The gene is expressed by cells grown in either diurnal light or in darkness, and there is no difference between the growth rates or cell yields of cultures grown in light or darkness.
视紫质是一种依赖光的质子泵，预计它通过为微生物代谢提供能量，在海洋生态中发挥重要作用。视紫质基因最初是通过对海水大型基因组DNA片段的克隆和测序发现的。后来发现它们广泛分布、系统发育多样且在海洋中具有活性。视紫质基因尚未在培养的细菌中发现，基于环境序列数据，目前还无法重建具有视紫质基因的未培养细菌菌株的基因组。尽管视紫质的代谢作用尚不确定，但人们认为它们在以溶解有机碳的异养同化作为主要代谢模式的细胞中发挥作用。在此我们报告，超丰富的SAR11进化枝的首个培养成员SAR11菌株HTCC1062（“嗜盐栖热袍菌”），在高压灭菌海水中以及在其天然环境海洋中培养时会表达视紫质基因。嗜盐栖热袍菌视紫质起到依赖光的质子泵的作用。该基因在昼夜光照或黑暗条件下生长的细胞中均有表达，光照或黑暗条件下培养的培养物的生长速率或细胞产量没有差异。
