THE EFFECTS ON ESCHERICHIA-COLI OF EXPRESSION OF THE CLONED BACTERIOPHAGE-T4 NUCLEOID DISRUPTION (NDD) GENE

Immediately after T4 bacteriophage infection, the Escherichia coli nuc leoid undergoes rapid delocalization. The ndd gene of T4 is responsibl e for this nuclear disruption phenomenon. We have cloned two alleles o f this gene and studied the effects of their expression on E. coli cel ls. We have shown that the Ndd protein (i) is able to reproduce the di sruption of the nucleoid characteristic of T4 infection, (ii) is highl y toxic and results in a logarithmic decrease in cell viability, and ( iii) inhibits genomic DNA replication by blocking progression of repli cation forks. Induction of Ndd does not result in degradation of genom ic DNA and does not significantly alter the general processes of trans cription and translation during the entire period of exponential cell death. These results support the notion that the target of Ndd is some aspect of the nucleoid architecture.