Roles of the Escherichia coli heat shock sigma factor 32 in early and late gene expression of bacteriophage T4

We have analyzed early and late T4 gene expression at the levels of transcription and translation in rpoH+ (sigma 32+) and rpoH mutant cells infected under heat shock conditions. We found, as expected, that Escherichia coli cells must be adapted before infection to high temperature by the heat shock response to allow early T4 transcription, subsequent late gene expression, and progeny production at 42 degrees C. Unexpectedly, we found in addition that when rpoH mutant (sigma 32 mutant) cells were shifted from 30 to 42 degrees C 10 min after infection, late T4 genes were not expressed, even though DNA synthesis appeared to be normal.