Spontaneous photosynthetic mutants of the aerobic anoxygenic phototrophic bacterium Roseicyclus mahoneyensis, strain ML6 have been identified based on phenotypic differences and spectrophotometric analysis. ML6 contains a reaction centre (RC) with absorption peaks at 755, 800, and 870 nm, light harvesting (LH) complex 1 at 870 nm, and monomodal LH2 at 805 nm; the mutant ML6(B) has only the LH2; ML6(DB) has also lost the LH1; in ML6(BN9O), the LH2 is absent and concentrations of LH1 and RC are much lower than in the wild type. RCs were isolated and purified from ML6 and ML6(BN9O); LH1-RC from ML6; and LH2 from ML6, ML6(B), and ML6(DB). All protein subunits composing the complexes were found to be of typical size. Flash-induced difference spectra revealed ML6 has a fully functional photosynthetic apparatus under aerobic and microaerophilic conditions, and as is typical for AAP, there is no photosynthetic activity anaerobically. ML6(BN9O), while also functional photosynthetically aerobically, showed lower rates due to the lack of LH2 and decreased concentrations of LH1 and RC. ML6(B) and ML6(DB) showed no photoinduced electron transport. Action spectra of light-mediated reactions were also performed on ML6 and ML6(BN9O) to reveal that the majority of carotenoids are not involved in light harvesting. Finally, redox titrations were carried out on membranes of ML6 and ML6(BN9O) to confirm that midpoint redox potentials of the QA, RC-bound cytochrome, and P+ were similar in both strains. QA midpoint potential is + 65 mV, cytochrome is + 245 mV, and P+ is + 430 mV.

中文翻译：

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有氧产氧光养菌玫瑰红轮虫及其自发突变体中的光合复合物和依赖光的电子传输链。

基于表型差异和分光光度分析，已经鉴定出好氧产氧光养细菌玫瑰红轮枝菌Rosycyclus mahoneyensis的自发光合突变株ML6。ML6包含一个反应中心（RC），其吸收峰在755、800和870 nm处，光收集（LH）络合物1在870 nm处，单峰LH2在805 nm处；突变体ML6（B）仅具有LH2；ML6（DB）也失去了LH1；在ML6（BN9O）中，LH2不存在，并且LH1和RC的浓度远低于野生型。从ML6和ML6（BN9O）中分离并纯化RC; ML6的LH1-RC；ML6，ML6（B）和ML6（DB）中的LH2。发现构成复合物的所有蛋白质亚基具有典型大小。闪光诱导的差异光谱显示，ML6在需氧和微需氧条件下具有功能齐全的光合装置，并且对于AAP而言是典型的，没有厌氧性的光合活性。ML6（BN9O）虽然也具有光合需氧功能，但由于缺少LH2以及降低了LH1和RC的浓度，其速率较低。ML6（B）和ML6（DB）没有显示出光致电子传输。还对ML6和ML6（BN9O）进行了光介导反应的作用谱，以揭示大多数类胡萝卜素不参与光收集。最后，在ML6和ML6（BN9O）的膜上进行了氧化还原滴定，以确认QA，RC结合的细胞色素和P +的中点氧化还原电位在这两个菌株中相似。QA中点电位为+ 65 mV，细胞色素为+ 245 mV，