Delayed nucleoid segregation in Escherichia coli.
To study the role of cell division in the process of nucleoid segregation, we measured the DNA content of individual nucleoids in isogenic Escherichia coli cell division mutants by image cytometry. In pbpB(Ts) and ftsZ strains growing as filaments at 42 degrees C, nucleoids contained, on average, more than two chromosome equivalents compared with 1.6 in wild-type cells. Because similar results were obtained with a pbpB recA strain, the increased DNA content cannot be ascribed to the occurrence of chromosome dimers. From the determination of the amount of DNA per cell and per individual nucleoid after rifampicin inhibition, we estimated the C and D periods (duration of a round of replication and time between termination and cell division respectively), as well as the D' period (time between termination and nucleoid separation). Compared with the parent strain and in contrast to ftsQ, ftsA and ftsZ mutants, pbpB(Ts) cells growing at the permissive temperature (28 degrees C) showed a long D' period (42 min versus 18 min in the parent) indicative of an extended segregation time. The results indicate that a defective cell division protein such as PbpB not only affects the division process but also plays a role in the last stage of DNA segregation. We propose that PbpB is involved in the assembly of the divisome and that this structure enhances nucleoid segregation.
Huls
P G
PG
Institute for Molecular Cell Biology, BioCentrum Amsterdam, University of Amsterdam, Kruislaan 316, 1098 SM Amsterdam, The Netherlands.
Vischer
N O
NO
Woldringh
C L
CL
D001398:Aztreonam / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002455:Cell Division / Q000235:genetics*; D020090:Chromosome Segregation; D002876:Chromosomes, Bacterial; D003598:Cytoskeletal Proteins; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D005434:Flow Cytometry / Q000379:methods; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics; D009154:Mutation; D046915:Penicillin-Binding Proteins; D046928:Peptidoglycan Glycosyltransferase; D010458:Peptidyl Transferases; D011938:Rec A Recombinases / Q000235:genetics; D013696:Temperature
D001426:Bacterial Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C478704:FtsI protein, E coli; C071525:FtsZ protein, Bacteria; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D046928:Peptidoglycan Glycosyltransferase; D011938:Rec A Recombinases; D002267:Muramoylpentapeptide Carboxypeptidase; D001398:Aztreonam