Zhang E, Ferenci T
Department of Microbiology G08, University of Sydney, N.S.W., Australia.
FEMS Microbiol Lett. 1999 Jul 15;176(2):395-401. doi: 10.1111/j.1574-6968.1999.tb13689.x.
The disaccharide lactose has no specific diffusion pathway across the outer membrane of Escherichia coli. At least three classes of spontaneous mutation affecting outer membrane permeability arose with each of three independent E. coli populations adapting to prolonged lactose limitation in chemostats. Both structural and regulatory mutations affecting OmpF porin predominated in isolates after 210-280 generations of culture. Six types of ompF mutation were found, including in-frame deletions and substitutions at Arg82 and Asp113, all affecting the channel constriction residues of OmpF. Isolates had increased susceptibility to antibiotics and were affected in the quantity of OmpF, LamB and OmpA proteins. A minimum of three or four mutations was evident in all isolates after 280 generations in a lactose-limited environment, in addition to lac mutations defined in previous studies.
二糖乳糖没有穿过大肠杆菌外膜的特定扩散途径。在三个独立的大肠杆菌群体适应恒化器中长时间乳糖限制的过程中，至少出现了三类影响外膜通透性的自发突变。在培养210 - 280代后，影响OmpF孔蛋白的结构和调控突变在分离株中占主导地位。发现了六种类型的ompF突变，包括框内缺失以及Arg82和Asp113处的替换，所有这些都影响OmpF的通道收缩残基。分离株对抗生素的敏感性增加，并且OmpF、LamB和OmpA蛋白的数量受到影响。在乳糖限制环境中培养280代后，除了先前研究中定义的lac突变外，所有分离株中至少有三到四个突变是明显的。
