title: LocZ is a new cell division protein involved in proper septum placement in Streptococcus pneumoniae.
abstract: How bacteria control proper septum placement at midcell, to guarantee the generation of identical daughter cells, is still largely unknown. Although different systems involved in the selection of the division site have been described in selected species, these do not appear to be widely conserved. Here, we report that LocZ (Spr0334), a newly identified cell division protein, is involved in proper septum placement in Streptococcus pneumoniae. We show that locZ is not essential but that its deletion results in cell division defects and shape deformation, causing cells to divide asymmetrically and generate unequally sized, occasionally anucleated, daughter cells. LocZ has a unique localization profile. It arrives early at midcell, before FtsZ and FtsA, and leaves the septum early, apparently moving along with the equatorial rings that mark the future division sites. Consistently, cells lacking LocZ also show misplacement of the Z-ring, suggesting that it could act as a positive regulator to determine septum placement. LocZ was identified as a substrate of the Ser/Thr protein kinase StkP, which regulates cell division in S. pneumoniae. Interestingly, homologues of LocZ are found only in streptococci, lactococci, and enterococci, indicating that this close phylogenetically related group of bacteria evolved a specific solution to spatially regulate cell division.
  
  
  OBJECTIVE
  Bacterial cell division is a highly ordered process regulated in time and space. Recently, we reported that the Ser/Thr protein kinase StkP regulates cell division in Streptococcus pneumoniae, through phosphorylation of several key proteins. Here, we characterized one of the StkP substrates, Spr0334, which we named LocZ. We show that LocZ is a new cell division protein important for proper septum placement and likely functions as a marker of the cell division site. Consistently, LocZ supports proper Z-ring positioning at midcell. LocZ is conserved only among streptococci, lactococci, and enterococci, which lack homologues of the Min and nucleoid occlusion effectors, indicating that these bacteria adapted a unique mechanism to find their middle, reflecting their specific shape and symmetry.
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Nela
authors.initials: N
authors.lastname: Holečková
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic linda@biomed.cas.cz omassid@unica.it.
authors.forename: Linda
authors.initials: L
authors.lastname: Doubravová
authors.affiliation: Dipartimento di Scienze Chirurgiche, Sez. di Anatomia Patologica e Microbiologia, Università di Cagliari, Cagliari, Italy linda@biomed.cas.cz omassid@unica.it.
authors.forename: Orietta
authors.initials: O
authors.lastname: Massidda
authors.affiliation: Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, Montpellier, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Molle
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Karolína
authors.initials: K
authors.lastname: Buriánková
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Oldřich
authors.initials: O
authors.lastname: Benada
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Olga
authors.initials: O
authors.lastname: Kofroňová
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Aleš
authors.initials: A
authors.lastname: Ulrych
authors.affiliation: Cell and Molecular Microbiology Division, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Branny
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D016983:Enterococcus / Q000235:genetics; D017353:Gene Deletion; D017045:Lactococcus / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000166:cytology / Q000235:genetics / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins