Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Microbiology (Reading). 2012 Aug;158(Pt 8):2180-2191. doi: 10.1099/mic.0.057877-0. Epub 2012 May 18.
The Sinorhizobium meliloti locus necessary for the utilization of erythritol as a sole carbon source, contains 17 genes, including genes that encode an ABC transporter necessary for the transport of erythritol, as well as the genes encoding EryA, EryB, EryC, TpiB and the regulators EryD and EryR (SMc01615). Construction of defined deletions and complementation experiments show that the other genes at this locus encode products that are necessary for the catabolism of adonitol (ribitol) and l-arabitol, but not d-arabitol. These analyses show that aside from one gene that is specific for the catabolism of l-arabitol (SMc01619, lalA), the rest of the catabolic genes are necessary for both polyols (SMc01617, rbtC; SMc01618, rbtB; SMc01622, rbtA). Genetic and biochemical data show that in addition to utilizing erythritol as a substrate, EryA is also capable of utilizing adonitol and l-arabitol. Similarly, transport experiments using labelled erythritol show that adonitol, l-arabitol and erythritol share a common transporter (MptABCDE). Quantitative RT-PCR experiments show that transcripts containing genes necessary for adonitol and l-arabitol utilization are induced by these sugars in an eryA-dependent manner.
苜蓿中华根瘤菌利用赤藓糖醇作为唯一碳源的必需基因座包含 17 个基因，包括编码赤藓糖醇转运所需的 ABC 转运蛋白的基因，以及编码 EryA、EryB、EryC、TpiB 和调控因子 EryD 和 EryR 的基因 (SMc01615)。通过构建明确的缺失和互补实验表明，该基因座上的其他基因编码的产物对于甘露醇（肌醇）和 L-阿拉伯糖醇的分解代谢是必需的，但对 D-阿拉伯糖醇则不是。这些分析表明，除了一个专门用于 L-阿拉伯糖醇分解代谢的基因（SMc01619，lalA）之外，其余的分解代谢基因对于两种多元醇（SMc01617，rbtC；SMc01618，rbtB；SMc01622，rbtA）都是必需的。遗传和生化数据表明，EryA 不仅可以利用赤藓糖醇作为底物，还可以利用甘露醇和 L-阿拉伯糖醇。同样，使用标记赤藓糖醇的运输实验表明，甘露醇、L-阿拉伯糖醇和赤藓糖醇共享一个共同的转运蛋白（MptABCDE）。定量 RT-PCR 实验表明，含有利用甘露醇和 L-阿拉伯糖醇所需基因的转录物以 EryA 依赖的方式被这些糖诱导。
