This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Suksomtip, M. Articles by Nester, E. W. Search for Related Content PubMed PubMed Citation Articles by Suksomtip, M. Articles by Nester, E. W.

Citrate Synthase Mutants of Agrobacterium Are Attenuated in Virulence and Display Reduced vir Gene Induction

Maneewan Suksomtip ,^, Pu Liu, Tamara Anderson, Sumalee Tungpradabkul, Derek W. Wood,^¶ and Eugene W. Nester^*

Department of Microbiology, Box 357242, University of Washington, Seattle, Washington 98195-7242

Received 7 January 2005/ Accepted 16 March 2005

A citrate synthase (CS) deletion mutant of Agrobacterium tumefaciens C58 is highly attenuated in virulence. The identity of the mutant was initially determined from its amino acid sequence, which is 68% identical to Escherichia coli and 77% identical to Brucella melitensis. The mutant lost all CS enzymatic activity, and a cloned CS gene complemented a CS mutation in Sinorhizobium. The CS mutation resulted in a 10-fold reduction in vir gene expression, which likely accounts for the attenuated virulence. When a plasmid containing a constitutive virG [virG(Con)] locus was introduced into this mutant, the level of vir gene induction was restored to nearly wild-type level. Further, the virG(Con)-complemented CS mutant strain induced tumors that were similar in size and number to those induced by the parental strain. The CS mutation resulted in only a minor reduction in growth rate in a glucose-salts medium. Both the CS mutant and the virG(Con)-complemented CS strain displayed similar growth deficiencies in a glucose-salts medium, indicating that the reduced growth rate of the CS mutant could not be responsible for the attenuated virulence. A search of the genome of A. tumefaciens C58 revealed four proteins, encoded on different replicons, with conserved CS motifs. However, only the locus that when mutated resulted in an attenuated phenotype has CS activity. Mutations in the other three loci did not result in attenuated virulence and any loss of CS activity, and none were able to complement the CS mutation in Sinorhizobium. The function of these loci remains unknown.

M.S. and P.L. have contributed equally to this work.

Present address: Dept. of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.

Present address: Fred Hutchinson Cancer Research Center, Basic Sciences Division, B2-135, 1100 Fairview Avenue North, Seattle, WA 98109.

^¶ Present address: Department of Biology, 3307 3rd Ave. W., Suite 205, Seattle Pacific University, Seattle, WA 98119.

This article has been cited by other articles:

• Saenkham, P., Eiamphungporn, W., Farrand, S. K., Vattanaviboon, P., Mongkolsuk, S. (2007). Multiple Superoxide Dismutases in Agrobacterium tumefaciens: Functional Analysis, Gene Regulation, and Influence on Tumorigenesis. J. Bacteriol. 189: 8807-8817 [Abstract] [Full Text]  
• Liu, P., Wood, D., Nester, E. W. (2005). Phosphoenolpyruvate Carboxykinase Is an Acid-Induced, Chromosomally Encoded Virulence Factor in Agrobacterium tumefaciens. J. Bacteriol. 187: 6039-6045 [Abstract] [Full Text]