Inhibition of Deoxyribonucleic Acid Synthesis and Bud Formation by Nalidixic Acid in Hyphomicrobium neptunium

The relationship between chromosome replication and morphogenesis in the budding bacterium Hyphomicrobium neptunium has been investigated. Nalidixic acid was found to completely inhibit deoxyribonucleic acid synthesis, but not ribonucleic acid synthesis. The antibiotic was bacteriostatic to the organism for the initial 5 h of exposure; thereafter it was bacteriocidal. Observation of inhibited cultures revealed cells that had produced abnormally long stalks, but no buds. These results indicate that bud formation is coupled to chromosome replication in H. neptunium. They do not exclude the possibilities that cross wall formation and bud separation may also be coupled to chromosome replication.