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Documentation of Auxotrophic Mutation in Blue-Green Bacteria: Characterization of a Tryptophan Auxotroph in Agmenellum quadruplicatum

^a Marine Science Institute, University of Texas, Port Aransas, Texas 78373; The University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences, and Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830; and Department of Microbiology, Baylor College of Medicine, Houston, Texas 77025

ABSTRACT

A tryptophan-requiring auxotroph of Agmenellum quadruplicatum strain BG1, a species of blue-green bacteria, was isolated by means of a nitrosoguanidine-penicillin procedure. Its growth characteristics were determined, and the enzymological block was identified in the A activity of tryptophan synthetase. Starvation of the auxotroph for tryptophan resulted in the derepression of the synthesis of all five enzymes. The first four enzymes derepressed 2- to 3-fold, and tryptophan synthetase B derepressed 20-fold. In the parental prototroph, BG1, anthranilate synthetase was active in crude extracts with ammonia as the amino donor reactant, but not with glutamine.

¹ Present address: Department of Microbiology, University of Tennessee Medical Units, Memphis, Tenn. 38103.

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• Xie, G., Keyhani, N. O., Bonner, C. A., Jensen, R. A. (2003). Ancient Origin of the Tryptophan Operon and the Dynamics of Evolutionary Change. Microbiol. Mol. Biol. Rev. 67: 303-342 [Abstract] [Full Text]