† Present address: Laboratory of Molecular Biology, National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20205, U.S.A.
The asymmetry of the DNA duplex due to polynucleotide strand complementarity could be the molecular basis of cell polarity in spore-forming bacteria. To test this possibility, the relationship of DNA strand segregation to the spore location pattern in chains of sporangia was investigated in Bacillus megaterium. Spores containing one chromosome labelled in one of the complementary strands were formed from cells that had been allowed to segregate pulse-labelled chromosomes in minimal medium at 30°C. A second crop of spores was then formed from cells originating from the labelled spore population. The second generation spores inherited labelled strands from the first spore population by random segregation. In contrast, the patterns of spore positions in sporangial chains were non-random. Furthermore, the non-randomness of patterning was stable and was unaffected by growth temperature (15 to 37 °C) or by enrichment of the minimal medium used in the segregation experiments. Since the pattern of DNA strand segregation is random and the spore location pattern in chains of sporangia is non-random, the asymmetry of the DNA duplex cannot be the determinant of cell polarity.
DunnG.,
MandelstamJ.1977; Cell polarity in Bacillus subtilis: effect of growth conditions on spore positions in sister cells. Journal of General Microbiology 103:201–205
FreeseE.,
HeinzeJ.,
MitaniT.,
FreeseE. B.1978; Limitation of nucleotides induces sporulation. In SporesVII pp. 277–285 Edited by ChamblissG.,
VaryJ. C.
Washington, D.C.: American Society for Microbiology.;
HitchinsA. D.1978a; Polarity and topology of DNA segregation and septation in cells and sporangia of the bacilli. Canadian Journal of Microbiology 24:1104–1134
JohnstoneK.,
EllarD. J.1978; Spore location patterns in sporulation doublets of Bacillus cereus and Bacillus megaterium, derived from single doublet isolates with differing sporulation geometry. Journal of Bacteriology 133:1024–1026
KonigsbergI. R.1979; Preface.Determinants of spatial organisation. In 37th Symposium of the Society for Developmental Biology pp. ix–xix Edited by SubtelnyS.,
KonigsbergI. R.
New York: Academic Press.;
SlepeckyR. A.,
FosterJ. W.1959; Alterations in metal content of spores of Bacillus megateriumand the effect on some properties. Journal of Bacteriology 78:117–123