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Journal of Bacteriology, January 2009, p. 320-332, Vol. 191, No. 1
0021-9193/09/$08.00+0     doi:10.1128/JB.00858-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Genetic Interactions of smc, ftsK, and parB Genes in Streptomyces coelicolor and Their Developmental Genome Segregation Phenotypes{triangledown} ,{dagger}

Rebekah M. Dedrick, Hans Wildschutte,{ddagger} and Joseph R. McCormick*

Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282

Received 23 June 2008/ Accepted 21 October 2008

The mechanisms by which chromosomes condense and segregate during developmentally regulated cell division are of interest for Streptomyces coelicolor, a sporulating, filamentous bacterium with a large, linear genome. These processes coordinately occur as many septa synchronously form in syncytial aerial hyphae such that prespore compartments accurately receive chromosome copies. Our genetic approach analyzed mutants for ftsK, smc, and parB. DNA motor protein FtsK/SpoIIIE coordinates chromosome segregation with septum closure in rod-shaped bacteria. SMC (structural maintenance of chromosomes) participates in condensation and organization of the nucleoid. ParB/Spo0J partitions the origin of replication using a nucleoprotein complex, assembled at a centromere-like sequence. Consistent with previous work, we show that an ftsK-null mutant produces anucleate spores at the same frequency as the wild-type strain (0.8%). We report that the smc and ftsK deletion-insertion mutants (ftsK' truncation allele) have developmental segregation defects (7% and 15% anucleate spores, respectively). By use of these latter mutants, viable double and triple mutants were isolated in all combinations with a previously described parB-null mutant (12% anucleate spores). parB and smc were in separate segregation pathways; the loss of both exacerbates the segregation defect (24% anucleate spores). For a triple mutant, deletion of the region encoding the FtsK motor domain and one transmembrane segment partially alleviates the segregation defect of the smc parB mutant (10% anucleate spores). Considerable redundancy must exist in this filamentous organism because segregation of some genomic material occurs 90% of the time during development in the absence of three functions with only a fourfold loss of spore viability. Furthermore, we report that scpA and scpAB mutants (encoding SMC-associated proteins) have spore nucleoid organization defects. Finally, FtsK-enhanced green fluorescent protein (EGFP) localized as bands or foci between incipient nucleoids, while SMC-EGFP foci were not uniformly positioned along aerial hyphae, nor were they associated with every condensing nucleoid.

* Corresponding author. Mailing address: Department of Biological Sciences, Duquesne University, Pittsburgh, PA 15282. Phone: (412) 396-4775. Fax: (412) 396-5907. E-mail: mccormick{at}duq.edu

{triangledown} Published ahead of print on 31 October 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Present address: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.

Journal of Bacteriology, January 2009, p. 320-332, Vol. 191, No. 1
0021-9193/09/$08.00+0     doi:10.1128/JB.00858-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Salerno, P., Larsson, J., Bucca, G., Laing, E., Smith, C. P., Flardh, K. (2009). One of the Two Genes Encoding Nucleoid-Associated HU Proteins in Streptomyces coelicolor Is Developmentally Regulated and Specifically Involved in Spore Maturation. J. Bacteriol. 191: 6489-6500 [Abstract] [Full Text]  
  • Kois, A., Swiatek, M., Jakimowicz, D., Zakrzewska-Czerwinska, J. (2009). SMC Protein-Dependent Chromosome Condensation during Aerial Hyphal Development in Streptomyces. J. Bacteriol. 191: 310-319 [Abstract] [Full Text]  


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