State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No.1 Beichen West Road, Chaoyang District, Beijing, 100101, China.
China General Microorganism Culture Collection Center, Institute of Microbiology, Chinese Academy of Sciences, No.1 Beichen West Road, Chaoyang District, Beijing, 100101, China.
ISME J. 2021 Jun;15(6):1844-1857. doi: 10.1038/s41396-020-00891-w. Epub 2021 Jan 15.
Bacteria that inhabit glaciers usually produce carotenoids. Here, we report that a group of zeaxanthin-producing glacial Flavobacterium exhibited light-promoted growth. Of the tested 47 strains, 45 showed increased growths but two died under illumination at 50 μmol photon m s. Light stimulation occurred mainly in either anoxic or nutrient-poor cultures, while the same levels of light promotion were found for that grown at 14 and 7 °C. Pigment assays identified overrepresentative zeaxanthin but trace retinal in the light promoted 45 strains, while flexirubin was exclusively in the light-lethal two. Genomic analysis revealed the gene cluster for zeaxanthin synthesis in the 45 strains, in which 37 strains also harbored the proteorhodopsin gene prd. Transcriptomic analysis found that light-induced expressions of both the zeaxanthin synthesis and proteorhodopsin genes. Whereas, deletion of the prd gene in one strain did not diminish light promotion, inhibition of zeaxanthin synthesis did. In comparison, no light promotion was determined in a glacier Cryobacterium luteum that produced a non-zeaxanthin-type carotenoid. Therefore, light stimulation on the glacial Flavobacterium is mostly likely related to zeaxanthin, which could provide better photoprotection and sustain membrane integrity for the organisms living in cold environments.
生活在冰川中的细菌通常会产生类胡萝卜素。在这里，我们报告了一组产生玉米黄质的冰川黄杆菌表现出光促进生长。在测试的 47 株菌中，有 45 株菌在 50μmol 光子 m-2 s-1 的光照下表现出生长增加，但有两株菌死亡。光照刺激主要发生在缺氧或营养贫乏的培养物中，而在 14 和 7°C 下生长的细菌也发现了相同水平的光促进作用。色素测定鉴定出光促进的 45 株菌中玉米黄质含量过高，但视黄醛含量很少，而只有在光致死的两株菌中存在 flexirubin。基因组分析揭示了 45 株菌中玉米黄质合成的基因簇，其中 37 株菌还含有视蛋白基因 prd。转录组分析发现，玉米黄质合成和视蛋白基因的表达都受到光照的诱导。然而，在一株菌中缺失 prd 基因并没有减少光促进作用，而抑制玉米黄质合成则会减少光促进作用。相比之下，产生非玉米黄质型类胡萝卜素的冰川 Cryobacterium luteum 中没有确定光促进作用。因此，冰川黄杆菌的光刺激很可能与玉米黄质有关，玉米黄质可为生活在寒冷环境中的生物体提供更好的光保护和维持膜完整性。
