Vartak N B, Lin C C, Cleary J M, Fagan M J, Saier M H
Department of Biology, University of California at San Diego, La Jolla 92093-0116, USA.
Microbiology (Reading). 1995 Sep;141 ( Pt 9):2339-50. doi: 10.1099/13500872-141-9-2339.
'Sphingomonas (formerly Pseudomonas) elodea' produces the industrially important polysaccharide gellan when grown in media containing glucose. Glucose catabolic enzymes and enzymes of central carbon metabolism were assayed in crude extracts of glucose-grown cultures of this bacterium. Based on these analyses it was concluded that glucose is converted to either gluconate or glucose 6-phosphate and that both of these products are converted to 6-phosphogluconate, a precursor for the Entner-Doudoroff (ED) and pentose phosphate pathways. Phosphoglucoisomerase (Pgi) activity was detected, but the lack of phosphofructokinase activity indicated that the Embden-Meyerhof glycolytic pathway is non-functional for glucose degradation. Thus, this bacterium utilizes glucose mainly via the ED and pentose phosphate pathways. Enzyme analyses suggested the involvement of glucose-6-phosphate dehydrogenase (Zwf) in glucose utilization and CO2 production. The zwf gene was cloned from 'S. elodea' and partially sequenced, and a null zwf mutant was constructed. This mutant exhibited no Zwf activity in in vitro assays, grew normally on glucose minimal medium and accumulated biomass (cells plus gellan) and produced CO2 at the same rates as the parental strain. Potential explanations for this finding are provided. Clones carrying the pgi gene were isolated fortuitously.
“伊乐藻鞘氨醇单胞菌（以前称为假单胞菌伊乐藻）”在含有葡萄糖的培养基中生长时会产生具有工业重要性的多糖结冷胶。对该细菌葡萄糖培养物的粗提物中的葡萄糖分解代谢酶和中心碳代谢酶进行了测定。基于这些分析得出结论，葡萄糖被转化为葡萄糖酸或6-磷酸葡萄糖，并且这两种产物都被转化为6-磷酸葡萄糖酸，它是Entner-Doudoroff（ED）途径和磷酸戊糖途径的前体。检测到磷酸葡萄糖异构酶（Pgi）活性，但缺乏磷酸果糖激酶活性表明Embden-Meyerhof糖酵解途径对葡萄糖降解不起作用。因此，这种细菌主要通过ED途径和磷酸戊糖途径利用葡萄糖。酶分析表明6-磷酸葡萄糖脱氢酶（Zwf）参与葡萄糖利用和二氧化碳产生。从“伊乐藻鞘氨醇单胞菌”中克隆了zwf基因并进行了部分测序，并构建了zwf基因缺失突变体。该突变体在体外测定中没有Zwf活性，在葡萄糖基本培养基上正常生长，积累生物量（细胞加结冷胶），并以与亲本菌株相同的速率产生二氧化碳。文中提供了对这一发现的可能解释。偶然分离到携带pgi基因的克隆。
