耐利福定大肠杆菌K—12包膜组分的生化分析

BIOCHEMICAL ANALYSIS OF BACTERIAL ENVELOPES OF RIFANDIN-SUSCEPTIBLE AND-RESISTANT STRAINS OF ESCHERICHIA COLI K-12

通过提取大肠杆菌K-12敏感株及其耐利福定株的包膜,并对其组分作了初步的生化分析。结果表明:十二烷基磺酸钠—聚丙烯酰胺凝胶电泳发现耐药株包膜蛋白质中一条分子量为52KD的蛋白带较相应敏感株包膜蛋白有明显减少;超薄膜层聚丙烯酰胺等电聚焦电泳分析提示敏感株与耐药株包膜蛋白的等电点无明显区别,均为4.5～6.7;氨基酸组成分析提示敏感株与耐药株包膜的各种氨基酸及其含量无明显区别;薄层色谱分析提示耐药菌膜脂较敏感菌膜脂多分离出1种组分,前者7种组分,后者仅6种组分;敏感株与耐药株包膜总含量分别为每毫克干重包膜含糖186.7±15.3和150.0±17.0微克。提示大肠杆菌K-12耐利福定后包膜屏障通透性的改变可能系蛋白质和脂类改变的结果。进一步的研究工作仍在继续之中。

The previous studiies have shown that one of the resistant mechanisms of E. colt and M. tuberculosis to rifandin(RFD)was related to a decrease of permeability of the bacteral envelope barrier to the antibiotic. In this paper, the bacterial cell envelopes were extracted from RFD-susceptible and -resistant strains of E. colt K-12 and their biochemical compositions were analyzed.SDS-PAGE of cell envelope proteins revealed a markedly diminished 52000 dalton protein in the resistant strain. Super-thin layer polyacrylamide gel isoelectric foqusing electrophoresis showed that there was no difference in the points of isoelectricity(pI) of cell envelope proteins between the susceptible and the resistant strains.Both pIs ranged from 4.5 to 6.7. Also noiqualitative and quantitive differences existed in amino acid compositions.Lipid analysis by thin-layer chromatography demonstraated that an additional spot was seen in the chromatogram of the resistant strain and also indicated that the resistant and the susceptible strains differed in total lipid content and in the relative proportion of individual lipids.The total carbohydrate contents from the resistant and the susceptible strains were 150. 0±17.0 and 186. 7±15.3 μg per mg of cell envelope (dry weight) respectively. The above results suggested that the alterations of protein and lipid probably resulted in the decrease of permeability of the bacterial envelope in RFD-resistant strain of E. colt K-12 to RFD.