title: Roles of the Essential Protein FtsA in Cell Growth and Division in Streptococcus pneumoniae.
abstract: Streptococcus pneumoniaeis an ovoid-shaped Gram-positive bacterium that grows by carrying out peripheral and septal peptidoglycan (PG) synthesis, analogous to model bacilli, such asEscherichia coliandBacillus subtilisIn the model bacilli, FtsZ and FtsA proteins assemble into a ring at midcell and are dedicated to septal PG synthesis but not peripheral PG synthesis; hence, inactivation of FtsZ or FtsA results in long filamentous cells unable to divide. Here, we demonstrate that FtsA and FtsZ colocalize at midcell inS. pneumoniaeand that partial depletion of FtsA perturbs septum synthesis, resulting in elongated cells with multiple FtsZ rings that fail to complete septation. Unexpectedly, complete depletion of FtsA resulted in the delocalization of FtsZ rings and ultimately cell ballooning and lysis. In contrast, depletion or deletion ofgpsBandsepF, which inB. subtilisare synthetically lethal withftsA, resulted in enlarged and elongated cells with multiple FtsZ rings, with deletion ofsepFmimicking partial depletion of FtsA. Notably, cell ballooning was not observed, consistent with later recruitment of these proteins to midcell after Z-ring assembly. The overproduction of FtsA stimulates septation and suppresses the cell division defects caused by the deletion ofsepFandgpsBunder some conditions, supporting the notion that FtsA shares overlapping functions with GpsB and SepF at later steps in the division process. Our results indicate that, inS. pneumoniae, both GpsB and SepF are involved in septal PG synthesis, whereas FtsA and FtsZ coordinate both peripheral and septal PG synthesis and are codependent for localization at midcell.IMPORTANCEStreptococcus pneumoniae(pneumococcus) is a clinically important human pathogen for which more therapies against unexploited essential targets, like cell growth and division proteins, are needed. Pneumococcus is an ovoid-shaped Gram-positive bacterium with cell growth and division properties that have important distinctions from those of rod-shaped bacteria. Gaining insights into these processes can thus provide valuable information to develop novel antimicrobials. Whereas rods use distinctly localized protein machines at different cellular locations to synthesize peripheral and septal peptidoglycans, we present evidence thatS. pneumoniaeorganizes these two machines at a single location in the middle of dividing cells. Here, we focus on the properties of the actin-like protein FtsA as an essential orchestrator of peripheral and septal growth in this bacterium.
authors.affiliation: Dipartimento di Scienze Chirurgiche, Università di Cagliari, Cagliari, Italy.|Institute of Microbiology of the Czech Academy of Sciences, Laboratory of Cell Signaling, Prague, Czech Republic.
authors.forename: Andrea
authors.identifier: http://orcid.org/0000-0002-7861-8690
authors.initials: A
authors.lastname: Mura
authors.affiliation: Dipartimento di Scienze Chirurgiche, Università di Cagliari, Cagliari, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Fadda
authors.affiliation: Department of Biology, Indiana University at Bloomington, Bloomington, Indiana, USA.
authors.forename: Amilcar J
authors.initials: AJ
authors.lastname: Perez
authors.affiliation: Department of Biology, Indiana University at Bloomington, Bloomington, Indiana, USA.
authors.forename: Madeline L
authors.initials: ML
authors.lastname: Danforth
authors.affiliation: Dipartimento di Scienze Chirurgiche, Università di Cagliari, Cagliari, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Musu
authors.affiliation: Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors.forename: Ana Isabel
authors.identifier: http://orcid.org/0000-0001-6021-3970
authors.initials: AI
authors.lastname: Rico
authors.affiliation: Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors.forename: Marcin
authors.initials: M
authors.lastname: Krupka
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Dalia
authors.initials: D
authors.lastname: Denapaite
authors.affiliation: Department of Biology, Indiana University at Bloomington, Bloomington, Indiana, USA.
authors.forename: Ho-Ching T
authors.initials: HT
authors.lastname: Tsui
authors.affiliation: Department of Biology, Indiana University at Bloomington, Bloomington, Indiana, USA.
authors.forename: Malcolm E
authors.initials: ME
authors.lastname: Winkler
authors.affiliation: Institute of Microbiology of the Czech Academy of Sciences, Laboratory of Cell Signaling, Prague, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Branny
authors.affiliation: Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors.forename: Miguel
authors.identifier: http://orcid.org/0000-0003-4193-8700
authors.initials: M
authors.lastname: Vicente
authors.affiliation: Department of Microbiology and Molecular Genetics, McGovern Medical School, Houston, Texas, USA William.Margolin@uth.tmc.edu omassid@unica.it.
authors.forename: William
authors.identifier: http://orcid.org/0000-0001-6557-7706
authors.initials: W
authors.lastname: Margolin
authors.affiliation: Dipartimento di Scienze Chirurgiche, Università di Cagliari, Cagliari, Italy William.Margolin@uth.tmc.edu omassid@unica.it.
authors.forename: Orietta
authors.identifier: http://orcid.org/0000-0001-8823-2372
authors.initials: O
authors.lastname: Massidda
keywords: FtsA; Gram-positive cocci; Streptococcus pneumoniae; cell division