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Journal of Bacteriology, November 2009, p. 6489-6500, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00709-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

One of the Two Genes Encoding Nucleoid-Associated HU Proteins in Streptomyces coelicolor Is Developmentally Regulated and Specifically Involved in Spore Maturation{triangledown} ,{dagger}

Paola Salerno,1,¶ Jessica Larsson,1 Giselda Bucca,2 Emma Laing,2 Colin P. Smith,2 and Klas Flärdh1*

Department of Cell and Organism Biology, Lund University, Sölvegatan 35, 22362 Lund, Sweden,1 Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7HX, United Kingdom2

Received 1 June 2009/ Accepted 17 August 2009

Streptomyces genomes encode two homologs of the nucleoid-associated HU proteins. One of them, here designated HupA, is of a conventional type similar to E. coli HU{alpha} and HUβ, while the other, HupS, is a two-domain protein. In addition to the N-terminal part that is similar to that of HU proteins, it has a C-terminal domain that is similar to the alanine- and lysine-rich C termini of eukaryotic linker histones. Such two-domain HU proteins are found only among Actinobacteria. In this phylum some organisms have only a single HU protein of the type with a C-terminal histone H1-like domain (e.g., Hlp in Mycobacterium smegmatis), while others have only a single conventional HU. Yet others, including the streptomycetes, produce both types of HU proteins. We show here that the two HU genes in Streptomyces coelicolor are differentially regulated and that hupS is specifically expressed during sporulation, while hupA is expressed in vegetative hyphae. The developmental upregulation of hupS occurred in sporogenic aerial hyphal compartments and was dependent on the developmental regulators whiA, whiG, and whiI. HupS was found to be nucleoid associated in spores, and a hupS deletion mutant had an average nucleoid size in spores larger than that in the parent strain. The mutant spores were also defective in heat resistance and spore pigmentation, although they possessed apparently normal spore walls and displayed no increased sensitivity to detergents. Overall, the results show that HupS is specifically involved in sporulation and may affect nucleoid architecture and protection in spores of S. coelicolor.

* Corresponding author. Mailing address: Department of Cell and Organism Biology, Lund University, Sölvegatan 35, 22362 Lund, Sweden. Phone: 46 46 2228584. Fax: 46 46 2224113. E-mail: klas.flardh{at}cob.lu.se

{triangledown} Published ahead of print on 28 August 2009.

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

Present address: Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom.

Journal of Bacteriology, November 2009, p. 6489-6500, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00709-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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