Deoxyribonucleic Acid Distribution in Bacillus subtilis Independent of Cell Elongation

A temperature-sensitive DNA(-) mutant of Bacillus subtilis has been studied during the resumption of deoxyribonucleic acid (DNA) synthesis following a 45 to 30 C temperature shift. For several hours after return to 30 C, DNA synthesis proceeds although the cells fail to elongate appreciably. Autoradiographs of cell populations synthesizing DNA during the recovery period demonstrate that DNA can become distributed to previously unoccupied regions along the cell length. By varying the labeling regime, newly synthesized DNA as well as DNA present at the time of transfer from 45 to 30 C were followed independently. Measurements of the percent of cell length covered by grains ((3)H-thymine in DNA) demonstrate the progressive refilling of DNA-vacant cell regions by both newly synthesized and original DNA. These data indicate that cell surface growth is not an absolute requirement for segregation of bacterial DNA.