Silva Pedro J N, Dykhuizen Daniel E
Department of Ecology and Evolution, State University of New York, Stony Brook, New York, 11794.
Departamento de Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, C2 Campo Grande, P-1700, Lisboa, Portugal.
Evolution. 1993 Jun;47(3):741-749. doi: 10.1111/j.1558-5646.1993.tb01230.x.
The fitness effects of six lac operons from natural isolates of Escherichia coli were determined in chemostats, in a test of the idea that selective differences among natural alleles are greater in novel conditions than in the prevailing environment, resulting in a greater genetic variance in fitness in novel conditions. Fitnesses were determined in the common milk sugar lactose, the natural substrate of the lac operon, and in three rare β-galactosides, lactulose, galactosyl-arabinose, and methyl-galactopyranoside, that are novel for E. coli. Significantly greater fitness differences were observed among the lac alleles in each of the novel β-galactosides than in lactose. An alternative explanation of the experimental findings is discussed. General evolutionary causes and consequences of selection potentials are discussed, and an outline of the work necessary to further elucidate the physiological basis of the observed potential for selection of the lac operon of E. coli is presented.
在恒化器中测定了来自大肠杆菌自然分离株的六个乳糖操纵子的适应性效应，以检验一种观点，即在新环境中自然等位基因之间的选择差异比在当前环境中更大，从而导致新环境中适应性的遗传方差更大。在乳糖操纵子的天然底物、常见的乳糖以及三种对大肠杆菌来说是新出现的罕见β-半乳糖苷（乳果糖、半乳糖基阿拉伯糖和甲基吡喃半乳糖苷）中测定了适应性。在每种新的β-半乳糖苷中观察到的乳糖等位基因之间的适应性差异显著大于在乳糖中的差异。讨论了对实验结果的另一种解释。讨论了选择潜力的一般进化原因和后果，并概述了进一步阐明观察到的大肠杆菌乳糖操纵子选择潜力的生理基础所需的工作。
