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DNA segregation by the bacterial actin AlfA during Bacillus subtilis growth and development
Author(s) -
Becker Eric,
Herrera Nick C,
Gunderson Felizza Q,
Derman Alan I,
Dance Amber L,
Sims Jennifer,
Larsen Rachel A,
Pogliano Joe
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601443
Subject(s) - biology , plasmid , bacillus subtilis , actin , microbiology and biotechnology , fluorescence recovery after photobleaching , dna , genetics , bacteria , membrane
We here identify a protein (AlfA; a ctin l ike f ilament) 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 <∼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.