title: Cell division site placement and asymmetric growth in mycobacteria.
abstract: Mycobacteria are members of the actinomycetes that grow by tip extension and lack apparent homologues of the known cell division regulators found in other rod-shaped bacteria. Previous work using static microscopy on dividing mycobacteria led to the hypothesis that these cells can grow and divide asymmetrically, and at a wide range of sizes, in contrast to the cell growth and division patterns observed in the model rod-shaped organisms. In this study, we test this hypothesis using live-cell time-lapse imaging of dividing Mycobacterium smegmatis labelled with fluorescent PBP1a, to probe peptidoglycan synthesis and label the cell septum. We demonstrate that the new septum is placed accurately at mid-cell, and that the asymmetric division observed is a result of differential growth from the cell tips, with a more than 2-fold difference in growth rate between fast and slow growing poles. We also show that the division site is not selected at a characteristic cell length, suggesting this is not an important cue during the mycobacterial cell cycle.
authors.affiliation: MRC Centre for Molecular Bacteriology and Infection, Department of Medicine, Imperial College, London, United Kingdom.
authors.forename: Graham
authors.initials: G
authors.lastname: Joyce
authors.forename: Kerstin J
authors.initials: KJ
authors.lastname: Williams
authors.forename: Matthew
authors.initials: M
authors.lastname: Robb
authors.forename: Elke
authors.initials: E
authors.lastname: Noens
authors.forename: Barbara
authors.initials: B
authors.lastname: Tizzano
authors.forename: Vahid
authors.initials: V
authors.lastname: Shahrezaei
authors.forename: Brian D
authors.initials: BD
authors.lastname: Robertson
mesh_terms: D002455:Cell Division; D020102:Mycobacterium smegmatis / Q000254:growth & development*; D046915:Penicillin-Binding Proteins / Q000378:metabolism
chemical_list: D046915:Penicillin-Binding Proteins