Wood Gwendolyn E, Haydock Andrew K, Leigh John A
Department of Microbiology, University of Washington, Seattle, Washington 98195-7242, USA.
J Bacteriol. 2003 Apr;185(8):2548-54. doi: 10.1128/JB.185.8.2548-2554.2003.
Methanococcus maripaludis is a mesophilic species of Archaea capable of producing methane from two substrates: hydrogen plus carbon dioxide and formate. To study the latter, we identified the formate dehydrogenase genes of M. maripaludis and found that the genome contains two gene clusters important for formate utilization. Phylogenetic analysis suggested that the two formate dehydrogenase gene sets arose from duplication events within the methanococcal lineage. The first gene cluster encodes homologs of formate dehydrogenase alpha (FdhA) and beta (FdhB) subunits and a putative formate transporter (FdhC) as well as a carbonic anhydrase analog. The second gene cluster encodes only FdhA and FdhB homologs. Mutants lacking either fdhA gene exhibited a partial growth defect on formate, whereas a double mutant was completely unable to grow on formate as a sole methanogenic substrate. Investigation of fdh gene expression revealed that transcription of both gene clusters is controlled by the presence of H(2) and not by the presence of formate.
海沼甲烷球菌是一种嗜温古菌，能够利用两种底物产生甲烷：氢气加二氧化碳以及甲酸盐。为了研究后者，我们鉴定了海沼甲烷球菌的甲酸盐脱氢酶基因，发现该基因组包含两个对甲酸盐利用至关重要的基因簇。系统发育分析表明，这两个甲酸盐脱氢酶基因集源自甲烷球菌谱系内的复制事件。第一个基因簇编码甲酸盐脱氢酶α（FdhA）和β（FdhB）亚基的同源物、一个推定的甲酸盐转运蛋白（FdhC）以及一种碳酸酐酶类似物。第二个基因簇仅编码FdhA和FdhB的同源物。缺乏任一fdhA基因的突变体在甲酸盐上表现出部分生长缺陷，而双突变体完全无法以甲酸盐作为唯一产甲烷底物生长。对fdh基因表达的研究表明，两个基因簇的转录均受H₂的存在调控，而非甲酸盐的存在调控。
