EXPRESSION AND FUNCTION OF BACTERIAL CELL SURFACE COMPONENTS

细菌细胞表面成分的表达和功能

• 批准号: 3941125
• 负责人: J FOULDS
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3941125
• 关键词: Escherichia coli; Salmonella; bacterial antigens; bacterial capsules; bacterial genetics; bacterial polysaccharides; complement pathway; drug resistance; gene expression; genetic strain; humoral immunity; lipopolysaccharides; membrane activity; membrane permeability

The polysaccharide, or O-antigen (O-Ag), portion of lipopolysaccharide (LPS) of Salmonellae plays a crucial role in the killing of these bacteria by the host humoral system. Specifically, the O-Ag structure directly effects the rate and extent of deposition of the complement component C3b on the cell surface by affecting the initial amount of C3b deposited and by influencing the subsequent interaction of this C3b with factor b. O-Ag structure does not influence the inactivation of bound C3b. Similarly, the O-Ag size and density on the surface of Salmonellae montevideo cells is responsible for the extent of killing of the cells by normal human serum. Survival in serum was associated with LPS that contained O-Ag side chains of at least 4-5 subunits in length and with about 20% of the LPS cores being substituted with O-Ag side chains of length more than 14 subunits. It is proposed that the O-Ag functions to provide serum resistance by sterically hindering access of the C5b-9 complex to the cell membrane. E. coli cells grown in the presence of 5 mM sodium salicylate become phenotypically resistant to a variety of antibiotics. This resistance begins within 5 minutes after the addition of salicylate and does not involve marked alterations in the pattern of protein or LPS isolated from the outer membrane. We have developed an assay to show that the salicylate-induced drug resistance is due to a 75-80% decrease in the permeability of the outer membrane.

多糖或O-抗原（O-Ag）部分， 沙门氏菌的脂多糖（LPS）在 宿主体液系统杀死这些细菌。 具体地说， O-Ag结构直接影响着 补体成分C3 b在细胞表面的沉积 通过影响C3 b沉积的初始量， 影响该C3 B与因子B的后续相互作用。 O-Ag结构不影响结合C3 b的失活。 同样地，在鲑鱼的表面上的O-Ag的尺寸和密度， 蒙得维的亚细胞负责杀死的程度， 正常人血清中的细胞。 血清存活率与 LPS含有至少4-5个亚基的O-Ag侧链 并且约20%的LPS核被取代 具有长度大于14个亚基的O-Ag侧链。 是 提出O-Ag的功能是提供血清抵抗力， 空间阻碍C5 b-9复合物进入细胞 膜的 E.在5 mM水杨酸钠存在下生长的大肠杆菌细胞 对多种抗生素产生表型耐药性。 这 在添加水杨酸盐后5分钟内开始产生抗性 并且不涉及蛋白质模式的显著改变， 或从外膜分离的LPS。 我们已经开发了一个 试验表明水杨酸诱导的耐药性是由于 外膜的渗透性降低75-80%。