DNA segregation by the bacterial actin AlfA during Bacillus subtilis growth and development.
We here identify a protein (AlfA; actin like filament) that defines a new family of actins that are only distantly related to MreB and ParM. AlfA is required for segregation of Bacillus subtilis plasmid pBET131 (a mini pLS32-derivative) during growth and sporulation. A 3-kb DNA fragment encoding alfA and a downstream gene (alfB) is necessary and sufficient for plasmid stability. AlfA-GFP assembles dynamic cytoskeletal filaments that rapidly turn over (t(1/2)< approximately 45 s) in fluorescence recovery after photobleaching experiments. A point mutation (alfA D168A) that completely inhibits AlfA subunit exchange in vivo is strongly defective for plasmid segregation, demonstrating that dynamic polymerization of AlfA is necessary for function. During sporulation, plasmid segregation occurs before septation and independently of the DNA translocase SpoIIIE and the chromosomal Par proteins Soj and Spo0J. The absence of the RacA chromosome anchoring protein reduces the efficiency of plasmid segregation (by about two-fold), suggesting that it might contribute to anchoring the plasmid at the pole during sporulation. Our results suggest that the dynamic polymerization of AlfA mediates plasmid separation during both growth and sporulation.
Becker
Eric
E
Division of Biological Sciences, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Herrera
Nick C
NC
Gunderson
Felizza Q
FQ
Derman
Alan I
AI
Dance
Amber L
AL
Sims
Jennifer
J
Larsen
Rachel A
RA
Pogliano
Joe
J
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000254:growth & development*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002455:Cell Division; D020090:Chromosome Segregation; D002876:Chromosomes, Bacterial / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism*; D015870:Gene Expression; D005798:Genes, Bacterial; D049452:Green Fluorescent Proteins / Q000378:metabolism; D019426:Integrases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013171:Spores, Bacterial / Q000502:physiology; D013234:Stem Cells / Q000166:cytology
D000199:Actins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; C030069:spore-specific proteins, Bacillus; D049452:Green Fluorescent Proteins; C045073:Cre recombinase; D019426:Integrases