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J Bacteriol. 1966 February; 91(2): 642-645
Copyright © 1966 American Society for Microbiology. All Rights Reserved.

Isolation and Characterization of Pyridoxine Auxotrophs of Escherichia coli1

Walter B. Dempsey and P. F. Pachler

a Department of Biochemistry, College of Medicine, University of Florida, Gainesville, Florida

ABSTRACT

DEMPSEY, WALTER B. (University of Florida, Gainesville), AND P. F. PACHLER. Isolation and characterization of pyridoxine auxotrophs of Escherichia coli. J. Bacteriol. 91:642–645. 1966.—Pyridoxine auxotrophs of Escherichia coli B have been consistently produced by a modified penicillin enrichment method. This modified penicillin technique included a 6-hr growth period in the absence of any pyridoxine followed by a 2-hr treatment with penicillin at 1,000 units per ml. Penicillin was removed from these cultures by membrane filtration and the process was repeated. A minimum of three cycles was found necessary to isolate auxotrophs. Different phenotypes within the group of pyridoxine auxotrophs were distinguished by their responses to feeding with the various forms of pyridoxine, as well as by cross-feeding tests. Two auxotrophs were also differentiated by their frequency of reversion to prototrophy. Cross-feeding tests indicated that seven of the phenotypes fed in a linear sequence. These phenotypes had a very low frequency of reversion. The auxotrophs with a high frequency of reversion cross-fed in a linear sequence and fed the first five of the other seven auxotrophs. One of the auxotrophs isolated was a pyridoxal auxotroph.

FOOTNOTES

1 This work was presented in part at the 65th Annual Meeting of the American Society for Microbiology, Atlantic City, N.J., 1965.

J Bacteriol. 1966 February; 91(2): 642-645
Copyright © 1966 American Society for Microbiology. All Rights Reserved.



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