EXAMINATION OF THE TN5 TRANSPOSASE OVERPRODUCTION PHENOTYPE IN ESCHERICHIA-COLI AND LOCALIZATION OF A SUPPRESSOR OF TRANSPOSASE OVERPRODUCTION KILLING THAT IS AN ALLELE OF RPOH

Tn5 transposase (Tnp) overproduction is lethal to Escherichia coli, Tn p overproduction causes cell filamentation, abnormal chromosome segreg ation, and an increase in anucleated cell formation, There are two sim ple explanations for the observed phenotype: induction of the SOS resp onse or of the heat shock response, The data presented here show that overproduction of Tnp neither induces an SOS response nor a strong hea t shock response, However, our experiments do indicate that induction of some sigma(32)-programmed function(s) (either due to an rpoH mutati on, a deletion of dnaK, or overproduction of sigma(32)) suppresses Tnp overproduction killing. This effect is not due to overproduction of D naK, DnaJ, or GroELS. In addition, Tnp but not Delta 11 Tnp (whose ove rproduction does not kill the host cells) associates with the inner ce ll membrane, suggesting a possible correlation between cell killing an d Tnp membrane association. These observations will he discussed in th e context of a model proposing that Tnp overproduction titrates an ess ential host factor(s) involved in an early cell division step and/or c hromosome segregation.