The following article requires a subscription:



(Format: HTML)

MUTATIONS are a double-edged sword: they are the ultimate source of genetic variation upon which evolution depends, yet most mutations affecting fitness (viability and reproductive success) appear to be harmful [1]. Deleterious mutations of small effect can escape natural selection, and should accumulate in small populations [2-4]. Reduced fitness from deleterious-mutation accumulation may be important in the evolution of sex [5-7], mate choice [8,9], and diploid life-cycles [10], and in the extinction of small populations [11,12]. Few empirical data exist, however. Minimum estimates of the genomic deleterious-mutation rate for viability in Drosophila melanogaster are surprisingly high [1,13,14], leading to the conjecture that the rate for total fitness could exceed 1.0 mutation per individual per generation [5,6]. Here we use Escherichia coli to provide an estimate of the genomic deleterious-mutation rate for total fitness in a microbe. We estimate that the per-microbe rate of deleterious mutations is in excess of 0.0002.

(C) 1996 Macmillan Magazines Ltd.