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Mutagenesis and Functional Selection Protocols for Directed Evolution of Proteins in E. coli
Published on: March 16, 2011
Some features of the mutability of bacteria during nonlethal selection
V G Godoy1, F S Gizatullin, M S Fox
1Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Abstract:
We describe the mutability of the Trp(-) chromosomal +1 frameshift mutation trpE7999 during nonlethal selection, finding that the appearance of Trp(+) revertants behaves similarly to that of episomal Lac(+) revertants. In addition, we show that a feature of the Lac(+) and Trp(+) mutability is the accumulation of Trp(+) and Lac(+) revertants with additional unselected mutations, most of which are not due to heritable mutators. The cells undergoing nonlethal selection apparently experience an epigenetic change resulting in a subset of bacteria with elevated mutability that often remain hypermutable for the duration of selection. The epigenetic change provoked by nonlethal selection appears to be mediated by a unique function provided by the F'128 episome.
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