[A novel type of phase variation regarding integrated and free states of plasmid pFDX163 in Bacillus stearothermophilus CU21].
pFDX1 is a recombinant plasmid which carries a foreign gene xylE. By selecting for kanamycin-resistant mutants of Bacillus stearothermophilus CU21(pFDX1) at higher temperature, a variant strain CU21-163 was obtained. This strain harbors a mutant plasmid pFDX163, which was formed by insertion of a 2.0kb H-fragment from the CU21 genome onto the plasmid pFDX1. pFDX163 was supposed to be integrated into the CU21 chromosome via homologous recombination of H-fragments. The CU21-163 strain consists of two cell types, i.e. y-cell and w-cell. The expression level of xylE gene in the former is higher than that in the latter. The progeny of a y-cell always contains some w-cells, while that of a w-cell contains y-cells. This is supposed to be due to a phase variation of CU21-163. Analysis on the amount of free and integrated plasmid DNA in different DNA samples of CU21-163 cells allows us to draw the conclusion that there are both free and integrated plasmids in the y-cells, whereas only integrated ones in the w-cells.
He
X S
XS
Institute of Genetics, Fudan University, Shanghai.
Shen
R Q
RQ
Sheng
Z J
ZJ
D015139:Blotting, Southern; D002374:Catalase / Q000032:analysis; D001411:Geobacillus stearothermophilus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D007612:Kanamycin / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D010957:Plasmids
D007612:Kanamycin; D002374:Catalase