Madigan Michael T, Sattley W Matthew, Kimura Yukihiro, Wang-Otomo Zheng-Yu
School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, USA.
Division of Natural Sciences, Indiana Wesleyan University, Marion, Indiana, USA.
Environ Microbiol. 2024 Feb;26(2):e16591. doi: 10.1111/1462-2920.16591.
The ecological success of purple sulfur bacteria (PSB) is linked to their ability to collect near-infrared solar energy by membrane-integrated, pigment-protein photocomplexes. These include a Core complex containing both light-harvesting 1 (LH1) and reaction centre (RC) components (called the LH1-RC photocomplex) present in all PSB and a peripheral light-harvesting complex present in most but not all PSB. In research to explain the unusual absorption properties of the thermophilic purple sulfur bacterium Thermochromatium tepidum, Ca was discovered bound to LH1 polypeptides in its LH1-RC; further work showed that calcium controls both the thermostability and unusual spectrum of the Core complex. Since then, Ca has been found in the LH1-RC photocomplexes of several other PSB, including mesophilic species, but not in the LH1-RC of purple non-sulfur bacteria. Here we focus on four species of PSB-two thermophilic and two mesophilic-and describe how Ca is integrated into and affects their photosynthetic machinery and why this previously overlooked divalent metal is a key nutrient for their ecological success.
紫色硫细菌（PSB）在生态上的成功与其通过膜整合色素蛋白光复合体收集近红外太阳能的能力有关。这些复合体包括一个核心复合体，所有PSB中都存在同时包含光捕获1（LH1）和反应中心（RC）成分的核心复合体（称为LH1-RC光复合体），以及大多数但并非所有PSB中存在的外周光捕获复合体。在解释嗜热紫色硫细菌嗜热栖热菌异常吸收特性的研究中，发现钙与它的LH1-RC中的LH1多肽结合；进一步的研究表明，钙控制着核心复合体的热稳定性和异常光谱。从那时起，在其他几种PSB的LH1-RC光复合体中也发现了钙，包括嗜温菌，但在紫色非硫细菌的LH1-RC中未发现。在这里，我们聚焦于四种PSB——两种嗜热菌和两种嗜温菌——并描述钙是如何整合到它们的光合机制中并影响光合机制的，以及为什么这种之前被忽视的二价金属是它们生态成功的关键营养物质。
