Al-Zarban S, Heffernan L, Nishitani J, Ransone L, Wilcox G
J Bacteriol. 1984 May;158(2):603-8. doi: 10.1128/jb.158.2.603-608.1984.
A total of 28 L-rhamnose-negative mutants in Salmonella typhimurium LT2 were all linked by P22 transduction and were classified into five groups on the basis of genetic and biochemical experiments. Deletion mapping showed that the gene order was rhaD rhaA rhaB rhaC rhaT . rhaA mutants lacked an inducible L-rhamnose isomerase, rhaB mutants lacked an inducible L- rhamnulokinase , and rhaD mutants were probably defective in L- rhamnulose -1-phosphate aldolase. Mutants that were unable to accumulate L-[14C]rhamnose but could grow on 1% L-rhamnose were designated rhaT to indicate a defect in L-rhamnose transport. Genetic evidence supports the hypothesis that the rhaC gene is a positive regulator of rha gene expression. (i) Pleiotropically negative mutants in the rhaC gene were isolated at a high frequency. (ii) Mutants containing an insertion or deletion within the rhaC gene had a pleiotropically negative phenotype. (iii) Complementation tests indicated that rhaC + was dominant to rhaC -. (iv) Rha+ revertants of deletion and Tn10 insertion mutations in the rhaC gene were isolated.
鼠伤寒沙门氏菌LT2中总共28个L-鼠李糖阴性突变体通过P22转导全部连锁，并根据遗传和生化实验分为五组。缺失作图表明基因顺序为rhaD、rhaA、rhaB、rhaC、rhaT。rhaA突变体缺乏可诱导的L-鼠李糖异构酶，rhaB突变体缺乏可诱导的L-鼠李糖激酶，rhaD突变体可能在L-鼠李糖-1-磷酸醛缩酶方面存在缺陷。无法积累L-[14C]鼠李糖但能在1% L-鼠李糖上生长的突变体被指定为rhaT，表明其在L-鼠李糖转运方面存在缺陷。遗传证据支持rhaC基因是rha基因表达的正调控因子这一假说。（i）在rhaC基因中以高频率分离到多效性阴性突变体。（ii）在rhaC基因内含有插入或缺失的突变体具有多效性阴性表型。（iii）互补试验表明rhaC+对rhaC-呈显性。（iv）分离到rhaC基因中缺失和Tn10插入突变的Rha+回复突变体。
