H. Willems et al., PLASMID-HOMOLOGOUS SEQUENCES IN THE CHROMOSOME OF PLASMIDLESS COXIELLA-BURNETII SCURRY Q217, Journal of bacteriology, 179(10), 1997, pp. 3293-3297
Chromosomal DNA from Coxiella burnetii Scurry Q217 was screened for th
e presence of plasmid-homologous sequences, Total DNA from Scurry Q217
was digested with NotI, and the resulting DNA fragments were separate
d by contour-clamped homogeneous electric field pulsed-field gel elect
rophoresis (CHEF-PFGE). Following hybridization with biotin-labeled Qp
H1 plasmid as a probe, two DNA fragments of 40 and 170 kb were identif
ied as targets, These fragments were cloned, and subclones containing
QpH1-homologous sequences were completely sequenced, The physical mapp
ing of DNA fragments was achieved by PCR with primers derived from adj
acent fragments, and a total of 18,360 bp was sequenced, Within the QD
H1-homolooous region spanning 16,624 bp, homology was as high as 99%.
Deletions were identified within EcoRI fragments A(H)-C-H-K-H-B-H (13,
490 bp) and J(H)-G(H)-E-H-L+-D-H (6,509 bp) and in fragment A(H) alone
(619 bp). An insertion of 744 bp was identified within the JD(C) regi
on of Scurry Q217. A search for putative coding regions identified a t
otal of 17 open reading frames (ORFs). Compared to plasmid QpH1, 6 ORF
s were identical, 5 ORFs were different in size, 6 ORFs were newly gen
erated, and 25 ORFs were lost, It was found that plasmid-homologous se
quences in Scurry Q217 were of chromosomal origin.