EXPRESSION ANALYSIS OF CLONED CHROMOSOMAL SEGMENTS OF ESCHERICHIA-COLI

The novel transcription system of bacteriophage T7 was used to express Escherichia coli genes preferentially with a new low-copy-number plas mid vector, pFN476, to minimize toxic gene effects. Selected E. coli c hromosomal fragments from an ordered genomic library (Y. Kohara, K. Ik iyama, and K. Isono, Cell 50:495-508, 1987) were recloned into this ve ctor, and their genes were preferentially expressed in vivo utilizing its T7 promoter. The protein products were analyzed by two-dimensional gel electrophoresis. By using DNA sequence information, the gel migra tion was predicted for the protein products of open reading frames fro m these segments, and this information was used to identify gene produ cts visualized as spots on two-dimensional gels. Even in the absence o f DNA sequence information, this approach offers the opportunity to id entify all gene products of E. coli and map their genes to within 10 k b on the E. coli genome; with sequence information, this approach can produce a definitive expression map of the E. coli genome.