Biotechnology Research Center, The University of Tokyo. 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan.
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo. 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan; Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan.
Res Microbiol. 2023 Nov-Dec;174(8):104131. doi: 10.1016/j.resmic.2023.104131. Epub 2023 Aug 26.
Biotin is an essential vitamin for all organisms. Some bacteria cannot synthesize biotin and live by acquiring biotin from the environment. Bacterial biotin transporters (BioY) are classified into three mechanistic types. The first forms the BioMNY complex with ATPase (BioM) and transmembrane protein (BioN). The second relies on a promiscuous energy coupling module. The third functions independently. One-third of bioY genes spread in bacteria cluster with bioM and bioN on the genomes, and the rest does not. Interestingly, some bacteria have the bioY gene clustering with bioB gene, which encodes biotin synthase, an enzyme that converts dethiobiotin to biotin, on their genome. This bioY-bioB cluster is observed even though these bacteria cannot synthesize biotin. Azorhizobium caulinodans ORS571, a rhizobium of tropical legume Sesbania rostrata, is one of such bacteria. In this study using this bacterium, we demonstrated that the BioY linked to BioB could transport not only biotin but also dethiobiotin, and the combination of BioY and BioB contributed to the growth of A. caulinodans ORS571 in a biotin-deficient but dethiobiotin-sufficient environment. We propose that such environment universally exists in the natural world, and the identification of such environment will be a new subject in the field of microbial ecology.
生物素是所有生物必需的维生素。有些细菌不能合成生物素，只能从环境中获取生物素。细菌生物素转运蛋白（BioY）分为三种机制类型。第一种与 ATP 酶（BioM）和跨膜蛋白（BioN）形成 BioMNY 复合物。第二种依赖于混杂的能量偶联模块。第三种独立发挥功能。三分之一的 bioY 基因在细菌中与 bioM 和 bioN 一起在基因组中扩散，其余的则没有。有趣的是，有些细菌的基因组上存在 bioY 基因与编码生物素合成酶的 bioB 基因聚类，该酶可将脱硫生物素转化为生物素。尽管这些细菌不能合成生物素，但仍能观察到这种 bioY-bioB 聚类。热带豆科植物 Sesbania rostrata 的根瘤菌 Azorhizobium caulinodans ORS571 就是其中之一。在本研究中，我们利用该细菌证明了与 BioB 相连的 BioY 不仅可以转运生物素，还可以转运脱硫生物素，并且 BioY 和 BioB 的组合有助于 A. caulinodans ORS571 在生物素缺乏但脱硫生物素充足的环境中生长。我们提出，这种环境在自然界中普遍存在，而识别这种环境将成为微生物生态学领域的一个新课题。
