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Journal of Bacteriology, October 1998, p. 5357-5368, Vol. 180, No. 20
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

A Chaperone in the HSP70 Family Controls Production of Extracellular Fibrils in Myxococcus xanthus

Robby M. Weimer,dagger Chad Creighton, Angela Stassinopoulos, Philip Youderian, and Patricia L. Hartzell*

Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, Idaho 83844-3052

Received 20 April 1998/Accepted 5 August 1998

Three independent Tn5-lac insertions in the S1 locus of Myxococcus xanthus inactivate the sglK gene, which is nonessential for growth but required for social motility and multicellular development. The sequence of sglK reveals that it encodes a homologue of the chaperone HSP70 (DnaK). The sglK gene is cotranscribed with the upstream grpS gene, which encodes a GrpE homologue. Unlike sglK, grpS is not required for social motility or development. Wild-type M. xanthus is encased in extracellular polysaccharide filaments associated with the multimeric fibrillin protein. Mutations in sglK inhibit cell cohesion, the binding of Congo red, and the synthesis or secretion of fibrillin, indicating that sglK mutants do not make fibrils. The fibR gene, located immediately upstream of the grpS-sglK operon, encodes a product which is predicted to have a sequence similar to those of the repressors of alginate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida. Inactivation of fibR leads to the overproduction of fibrillin, suggesting that M. xanthus fibril production and Pseudomonas alginate production are regulated in analogous ways. M. xanthus and Pseudomonas exopolysaccharides may play similar roles in a mechanism of social motility conserved in these gram-negative bacteria.

* Corresponding author. Mailing address: Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, ID 83844-3052. Phone: (208) 885-0572. Fax: (208) 885-6518. E-mail: hartzell{at}uidaho.edu.

dagger Present address: Department of Biology, University of Utah, Salt Lake City, UT 84112.

Journal of Bacteriology, October 1998, p. 5357-5368, Vol. 180, No. 20
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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