Influence of the nucleoid and the early stages of DNA replication on positioning the division site in Bacillus subtilis

Although division site positioning in rod-shaped bacteria is generally believed to occur through the combined effect of nucleoid occlusion and the Min system, several lines of evidence suggest the existence of additional mechanisms. Studies using outgrown spores of Bacillus subtilis have shown that...

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Bibliographic Details
Published in:Molecular microbiology 2010-05, Vol.76 (3), p.634-647
Main Authors: Moriya, S, Rashid, R.A, Rodrigues, C.D. Andrade, Harry, E.J
Format: Article
Language:English
Subjects:
Bacillus subtilis
Bacillus subtilis - cytology
Bacillus subtilis - genetics
Bacillus subtilis - metabolism
Bacteria
Bacterial Proteins
Bacteriology
Biological and medical sciences
Cell Division
Cell Nucleolus - genetics
Cell Nucleolus - metabolism
Deoxyribonucleic acid
DNA
DNA Replication
Fundamental and applied biological sciences. Psychology
Intranuclear Inclusion Bodies - genetics
Intranuclear Inclusion Bodies - metabolism
Microbiology
Miscellaneous
Morphology
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Summary:Although division site positioning in rod-shaped bacteria is generally believed to occur through the combined effect of nucleoid occlusion and the Min system, several lines of evidence suggest the existence of additional mechanisms. Studies using outgrown spores of Bacillus subtilis have shown that inhibiting the early stages of DNA replication, leading up to assembly of the replisome at oriC, influences Z ring positioning. Here we examine whether Z ring formation at midcell under various conditions of DNA replication inhibition is solely the result of relief of nucleoid occlusion. We show that midcell Z rings form preferentially over unreplicated nucleoids that have a bilobed morphology (lowering DNA concentration at midcell), whereas acentral Z rings form beside a single-lobed nucleoid. Remarkably however, when the DnaB replication initiation protein is inactivated midcell Z rings never form over bilobed nucleoids. Relieving nucleoid occlusion by deleting noc increased midcell Z ring frequency for all situations of DNA replication inhibition, however not to the same extent, with the DnaB-inactivated strain having the lowest frequency of midcell Z rings. We propose an additional mechanism for Z ring positioning in which the division site becomes increasingly potentiated for Z ring formation as initiation of replication is progressively completed.
ISSN:0950-382X
1365-2958
DOI:10.1111/j.1365-2958.2010.07102.x