The influences of a lambda prophage on the growth rate of Escherichia coli.

A lambda prophage increases the competitive ability of E. coli K12 in a glucose-limited chemostat. This phenomenon does not involve the lambdarex gene. Expression of the lambdarex gene conditionally decreases fitness in two ways: (1) it causes malT- but not malT+ lysogens to be at a selective disadvantage in competition with non-lysogens. (2) During adaptation to slow, glucose-limited chemostat growth from rapid, glucose-excess flask growth, expression of the lambdarex gene transiently decreases the growth rate when compared to the non-lysogen.