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Journal of Bacteriology, August 2009, p. 5216-5223, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00390-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Hopanoids Are Not Essential for Growth of Streptomyces scabies 87-22{triangledown}

Ryan F. Seipke and Rosemary Loria*

Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York 14853

Received 22 March 2009/ Accepted 29 May 2009

Hopanoids are triterpenoic, pentacyclic compounds that are structurally similar to sterols, which are required for normal cell function in eukaryotes. Hopanoids are thought to be an important component of bacterial cell membranes because they control membrane fluidity and diminish passive diffusion of ions, and a few taxons modulate their hopanoid content in response to environmental stimuli. However, to our knowledge, mutational studies to assess the importance of hopanoids in bacterial physiology have never been performed. Genome sequencing of the potato scab pathogen, Streptomyces scabies 87-22, revealed a hopanoid biosynthetic gene cluster (HBGC) that is predicted to synthesize hopene and aminotrihydroxybacteriohopane products. Hopene was produced by fully sporulated cultures of S. scabies on solid ISP4 (International Streptomyces Project 4) medium as well as by submerged mycelia grown in liquid minimal medium. The elongated hopanoid aminotrihydroxybacteriohopane was not detected under either growth condition. Transcription of the S. scabies HBGC was upregulated during aerial growth, which suggests a link between hopanoid production and morphological development. Functional analysis of the S. scabies {Delta}hop615-1 and {Delta}hop615-7 mutant strains, the first hopanoid mutants created in any bacterial taxon, revealed that hopanoids are not required for normal growth or for tolerance of ethanol, osmotic and oxidative stress, high temperature, or low pH. This suggests that hopanoids are not essential for normal streptomycete physiology.

* Corresponding author. Mailing address: 334 Plant Science Building, Cornell University, Ithaca, NY 14853. Phone: (607) 255-7831. Fax: (607) 255-4471. E-mail: rl21{at}cornell.edu

{triangledown} Published ahead of print on 5 June 2009.

Journal of Bacteriology, August 2009, p. 5216-5223, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00390-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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