Austin E A, Graves J F, Hite L A, Parker C T, Schnaitman C A
Department of Microbiology, University of Virginia Medical School, Charlottesville 22908.
J Bacteriol. 1990 Sep;172(9):5312-25. doi: 10.1128/jb.172.9.5312-5325.1990.
Tn10 insertions were selected on the basis of resistance to the lipopolysaccharide (LPS)-specific bacteriophage U3. The majority of these were located in a 2-kilobase region within the rfa locus, a gene cluster of about 18 kb that contains genes for LPS core biosynthesis. The rfa::Tn10 insertions all exhibited a deep rough phenotype that included hypersensitivity to hydrophobic antibiotics, a reduction in major outer membrane proteins, and production of truncated LPS. These mutations were complemented by a Clarke-Carbon plasmid known to complement rfa mutations of Salmonella typhimurium, and analysis of the insert from this plasmid showed that it contained genes for at least six polypeptides which appear to be arranged in the form of a complex operon. Defects in two of these genes were specifically implicated as the cause of the deep rough phenotype. One of these appeared to be rfaG, which encodes a function required for attachment of the first glucose residue to the heptose region of the core. The other gene did not appear to be directly involved in determination of the sugar composition of the core. We speculate that the product of this gene is involved in the attachment of phosphate or phosphorylethanolamine to the core and that it is the lack of one of these substituents which results in the deep rough phenotype.
基于对脂多糖（LPS）特异性噬菌体U3的抗性选择Tn10插入。其中大多数位于rfa基因座内一个2千碱基的区域，rfa基因座是一个约18 kb的基因簇，包含LPS核心生物合成的基因。rfa::Tn10插入均表现出深粗糙表型，包括对疏水性抗生素过敏、主要外膜蛋白减少以及截短LPS的产生。这些突变由已知可互补鼠伤寒沙门氏菌rfa突变的Clarke-Carbon质粒互补，对该质粒插入片段的分析表明，它包含至少六种多肽的基因，这些多肽似乎以复杂操纵子的形式排列。其中两个基因的缺陷被明确认为是深粗糙表型的原因。其中一个似乎是rfaG，它编码将第一个葡萄糖残基连接到核心庚糖区域所需的功能。另一个基因似乎没有直接参与核心糖组成的决定。我们推测该基因的产物参与将磷酸或磷酸乙醇胺连接到核心，并且正是缺乏这些取代基之一导致了深粗糙表型。
