UNLINKED LOCI AFFECTING RELATED BIOSYNTHETIC STEPS IN PSEUDOMONAS AERUGINOSA

BIOCHEMICAL AND GENETIC GROUPING OF ISOLEUCINE-VALINE MUTANTS OF PSEUDOMONAS AERUGINOSA

Pearce, L. E. (University of Otago, Dunedin, New Zealand), and J. S. Loutit. Biochemical and genetic grouping of isoleucine-valine mutants of Pseudomonas aeruginosa. J. Bacteriol. 89:58-63. 1965.-Isoleucine- and valine-requiring mutants of Pseudomonas aeruginosa, induced with ultraviolet and ethyl-methane-sulfonate, were isolated. The feeding properties and growth requirements of 56 of these mutants were examined, and evidence was found for at least four phenotypic groups, A, B, C, and D, controlling the biosynthesis of isoleucine and valine. Preliminary genetic mapping by use of bacteriophage-mediated transduction showed linkage between the mutant loci within groups A, B, and C. There was also evidence of linkage between the genes controlling groups A and B and some slight evidence of linkage between the other groups. There was insufficient evidence to suggest the arrangement of the genes.

NEW DATA ON THE LINKAGE MAP OF STREPTOMYCES COELICOLOR

Linkage data, obtained by a combination of selective analysis of haploid recombinants and analysis of segregating heterozygotes, are given for twenty-eight loci inStreptomyces coelicolorA3(2). This brings the total known loci for the organism to thirty-nine. The two linkage groups previously recognized remain separate, and their lengths have been increased to about 60 and 70 recombination units respectively. Whether the two linkage groups correspond to two chromosomes remains an open question.

Three further examples of close linkage of pairs of functionally related loci have been found (a trio of such loci was already known), and three other pairs provide possible examples of the same phenomenon. Some loci which are clustered inSalmonellaare unlinked inStreptomyces.

Linkage map of Pseudomonas aeruginosa PAT

The locations of new markers relative to markers previously mapped on the chromosome of Pseudomonas aeruginosa strain PAT were defined by generalized transduction with phage F116L and F1083. Although the marker orders of the various marker groups were deduced mainly from the results of two-factor crosses, the locations of a number of markers were confirmed by three-factor crosses. A linkage map of the chromosome of P. aeruginosa PAT was constructed which shows the relative locations of 50 genes. From the available data, the linkage maps of P. aeruginosa strains PAO and PAT appear to be similar.

Suppression of fluorophenylalanine resistance by mutation to streptomycin resistance in Pseudomonas aeruginosa

Waltho, Judith A. (University of Melbourne, Victoria, Australia), and B. W. Holloway. Suppression of fluorophenylalanine resistance by mutation to streptomycin resistance in Pseudomonas aeruginosa. J. Bacteriol. 92:35-42. 1966.-Fluorophenylalanine-resistant mutants (fpa-r) of Pseudomonas aeruginosa have been isolated. By cotransduction analysis, the mutations were shown to have at least two chromosomal locations. One locus (fpaA) showed linkage to three other markers, str, try-3bi, and arg-3, and the order of these four linked markers was found to be try-3bi, arg-3, fpaA, str. The linkage relationships of the other fpa loci are not yet known. The phenotypic expression of resistance at the fpaA locus can be suppressed by mutation of the str locus from str-s to str-r, whereas that at an unlinked fpa locus cannot.