Overproduction of <i>hisH</i> and <i>hisF</i> gene products leads to inhibition of cell division in <i>Salmonella</i>

Abstract

Salmonella typhimurium derepressed for the histidine biosynthetic enzymes form wrinkled colonies at 37 °C on media containing a high (2%) content of metabolizable carbon source. "Wrinkledness" reflects accumulation of multinucleate filamentous cells caused by impaired cell division. At 42 °C, DNA synthesis and nuclear division are impaired. Addition of methionine at 42 °C permits DNA synthesis, nuclear division, and, under some conditions, cell division. However, multinucleate filaments are formed both on high and on low carbon source at 42 °C. The filaments contain nuclei that are peculiarly hypersensitive to inactivation with ultraviolet (uv.) light.Overproduction of both the hisH and hisF gene products is required for these pleiotropic effects of derepression. The hisH and hisF proteins, and even some of their enzymologically inactive forms, may cooperate to inhibit cell division by direct interaction with (a) sensitive cellular site(s).