Chistoserdova Ludmila, Gomelsky Larissa, Vorholt Julia A, Gomelsky Mark, Tsygankov Yuri D, Lidstrom Mary E
Departments of Chemical Engineering1 and Microbiology2, University of Washington, Seattle, WA 98195, USA.
Institute of Genetics and Selection of Industrial Micro-organisms, 1st Dorozhny proezd 1, Moscow 113545, Russia4.
Microbiology (Reading). 2000 Jan;146 ( Pt 1):233-238. doi: 10.1099/00221287-146-1-233.
The roles of cyclic formaldehyde oxidation via 6-phosphogluconate dehydrogenase and linear oxidation via the tetrahydromethanopterin (H4MPT)-linked pathway were assessed in an obligate methylotroph, Methylobacillus flagellatus KT, by cloning, sequencing and mutating two chromosomal regions containing genes encoding enzymes specifically involved in these pathways: 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase and methenyl H4MPT cyclohydrolase (gndA, zwf and mch). No null mutants were obtained in gndA or zwf, implying that the cyclic oxidation of formaldehyde is required for C1 metabolism in this obligate methylotroph, probably as the main energy-generating pathway. In contrast, null mutants were generated in mch, indicating that the H4MPT-linked pathway is dispensable. These mutants showed enhanced sensitivity to formaldehyde, suggesting that this pathway plays a secondary physiological role in this methylotroph. This function is in contrast to Methylobacterium extorquens AM1, in which the H4MPT-linked pathway is essential.
通过克隆、测序和突变两个染色体区域，评估了专性甲基营养菌鞭毛甲基杆菌KT中经由6-磷酸葡萄糖酸脱氢酶的环状甲醛氧化作用以及经由四氢甲蝶呤（H4MPT）连接途径的线性氧化作用，这两个染色体区域包含编码这些途径中特异性参与的酶的基因：6-磷酸葡萄糖酸脱氢酶、葡萄糖-6-磷酸脱氢酶和亚甲基H4MPT环水解酶（gndA、zwf和mch）。在gndA或zwf中未获得无效突变体，这意味着甲醛的环状氧化对于这种专性甲基营养菌的C1代谢是必需的，可能作为主要的能量产生途径。相反，在mch中产生了无效突变体，表明H4MPT连接途径是可有可无的。这些突变体对甲醛表现出更高的敏感性，表明该途径在这种甲基营养菌中发挥次要的生理作用。该功能与嗜甲基甲基杆菌AM1相反，在嗜甲基甲基杆菌AM1中H4MPT连接途径是必不可少的。
