The recognition of a new family of rhodopsins in marine planktonic bacteria, proton-pumping proteorhodopsin, expanded the known phylogenetic range, environmental distribution, and sequence diversity of retinylidene photoproteins. At the time of this discovery, microbial ion-pumping rhodopsins were known solely in haloarchaea inhabiting extreme hypersaline environments. Shortly thereafter, proteorhodopsins and other light-activated energy-generating rhodopsins were recognized to be widespread among marine bacteria. The ubiquity of marine rhodopsin photosystems now challenges prior understanding of the nature and contributions of "heterotrophic" bacteria to biogeochemical carbon cycling and energy fluxes. Subsequent investigations have focused on the biophysics and biochemistry of these novel microbial rhodopsins, their distribution across the tree of life, evolutionary trajectories, and functional expression in nature. Later discoveries included the identification of proteorhodopsin genes in all three domains of life, the spectral tuning of rhodopsin variants to wavelengths prevailing in the sea, variable light-activated ion-pumping specificities among bacterial rhodopsin variants, and the widespread lateral gene transfer of biosynthetic genes for bacterial rhodopsins and their associated photopigments. Heterologous expression experiments with marine rhodopsin genes (and associated retinal chromophore genes) provided early evidence that light energy harvested by rhodopsins could be harnessed to provide biochemical energy. Importantly, some studies with native marine bacteria show that rhodopsin-containing bacteria use light to enhance growth or promote survival during starvation. We infer from the distribution of rhodopsin genes in diverse genomic contexts that different marine bacteria probably use rhodopsins to support light-dependent fitness strategies somewhere between these two extremes.

中文翻译：

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海洋细菌和古细菌离子泵视紫红质：遗传多样性，生理学和生态学。

认识到海洋浮游细菌中视紫红质的新家族，质子泵送的视紫红质，扩大了视黄叉光蛋白的已知系统发育范围，环境分布和序列多样性。在这一发现之时，仅在居住于极端高盐环境中的盐生菌中才知道了微生物的离子泵视紫红质。此后不久，人们就认为蛋白视紫红质和其他光活化能产生的视紫红质在海洋细菌中很普遍。现在，海洋视紫红质光系统的普遍性挑战了对“异养”细菌的性质及其对生物地球化学碳循环和能量通量的贡献的先前理解。随后的研究集中在这些新型微生物视紫红质的生物物理和生物化学上，它们在生命树，进化轨迹和自然界中的功能性表达中的分布。后来的发现包括在生活的所有三个领域中识别蛋白视紫红质基因，视紫红质变种的光谱调谐至海洋中普遍存在的波长，细菌视紫红质变种之间可变的光激活离子泵特异性以及生物合成基因的广泛侧向基因转移用于细菌视紫红质及其相关的色素。使用海洋视紫红质基因（和相关的视网膜生色团基因）的异源表达实验提供了早期证据，表明视紫红质所收集的光能可以用来提供生化能。重要的，对天然海洋细菌的一些研究表明，含视紫红质的细菌在饥饿期间利用光来增强生长或促进生存。我们从视紫红质基因在不同基因组环境中的分布推断出，不同的海洋细菌可能使用视紫红质来支持这两个极端之间的光依赖性适应策略。