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

Suppressor mutation in Pseudomonas aeruginosa

Suppressor mutations were identified in Pseudomonas aeruginosa, and a comparison was made with Escherichia coli suppressor systems. A suppressor-sensitive (sus) derivative of a plasmid, RP4 trp, and several Sus mutants of IncP1 plasmid-specific phages, were isolated by using E. coli. Plasmid RP4 trp (sus) was transferred to P. aeruginosa strains carrying trp markers which did not complement RP4 trp(sus), and Trp+ variants were selected. Some, but not all such revertants, could propagate PRD1 Sus phages, and these mutants were found to be supressor positive. Plating efficiencies of various Sus phages on these strains were compared with on E. coli strains carrying known suppressor genes. The results suggested that the Pseudomonas suppressors were probably amber suppressors. In iddition, some Sus phages (PRD1sus-55, PRD1sus-56) were obtained which, although apparently of the amber type for E. coli, were able to propagate equally well on sup+ or sup strains of P. aeruginosa. On the other hand, several mutants of phage PRR1 which were suppressed in E. coli were not suppressed by the P. aeruginosa suppressor. Suppressor-sensitive mutants were also isolated with P. aeruginosa bacteriophages E79 and D3.

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.

Appearance of straight flagellar filaments in the presence of p-fluorophenylalanine in Pseudomonas aeruginosa

In the presence of p-fluorophenylalanine, a normally flagellated strain of Pseudomonas aeruginosa produced straight flagellar filaments at the distal ends of preexisting flagella, indicating polar growth on its flagella.

Male-specific bacteriophage MS2 propagation in fluorophenylalanine-resistant Escherichia coli K12

Mutation of Escherichia coli K12 HfrH to resistance to fluorophenylalanine resulted in changes in the plaque morphology of bacteriophage MS2 on this strain and led to an increased efficiency of propagation of the phage in liquid cultures. Evidence was obtained that the mutation resulted in inhibition of early lysis in infected cells and that lysis involved the production of a lysozyme. Genetic studies suggested that the observed pleiotropy of the resistance mutation was due to informational suppression.

Genetic analysis of phenylalanine-responding mutants of Pseudomonas aeruginosa

A transduction analysis of phenylalanine-responding mutants of Pseudomonas aeruginosa revealed the existence of six unlinked genes. Enzyme assays showed that one gene was involved in the terminal production of phenylalanine (chorismate mutase), and the remaining five genes were involved in the common pathway of aromatic amino acid biosynthesis.

Chromosome mapping in Pseudomonas aeruginosa

A more extensive linkage map ofPseudomonas aeruginosastrain PAO has been compiled from data obtained by both, conjugation and transduction procedures. All the markers examined are located on one linkage group and the available evidence suggests that the sex factor FP2 promotes transfer of the chromosome in a polarized manner from only one site on this linkage group.

A mutant sex factor of Pseudomonas aeruginosa

A mutant with the properties of a recipient has been isolated from theP. aeruginosadonor strain PAT (FP 2 + ) following treatment with the acridine-mustard ICR-191. While this strain displays the properties expected of a female or recipient in a number of genetic tests, the FP 2 determined property of mercury resistance is retained by the strain, suggesting that it may carry the FP2 factor in a mutated form. Treatment of the donor strain PAT (FP2 + ) with acridine-mustard has produced mutant male strains with the ability to form recombinants with other male strains at frequencies similar to that obtained in FP2+ × FP2 − matings. This characteristic has been shown to be due to a mutation in the FP2 factor which is dominant to the wild-type function. The isolation of stable male strains carrying both the mutant and wild type forms of the sex factor suggests that more than one copy of the FP 2 factor occurs inP. aeruginosastrain PAT donors.

Significance of altered carbon flow in aromatic amino acid synthesis: an approach to the isolation of regulatory mutants in Pseudomonas aeruginosa

Pseudomonas aeruginosa displays a native resistance to a variety of inhibitory compounds, including many analogues of amino acids, purines, and pyrimidines. Therefore, it has been difficult to isolate analogue-resistant regulatory mutants which have been so valuable in other microbial species for the study of enzyme control mechanisms and for the study of amino acid transport and its regulation. However, we have found that increased sensitivity to growth inhibition by analogues can be demonstrated by manipulation of the nutritional environment. When P. aeruginosa is grown with fructose as the nutritional source of carbon and energy, the cells become sensitive to growth inhibition by beta-2-thienylalanine and p-amino-phenylalanine, analogues of phenylalanine and tyrosine, respectively. Thus, mutants were isolated which are resistant to growth inhibition by beta-2-thienylalanine and p-amino-phenylalanine when fructose is the carbon source, and many of the beta-2-thienylalanine-resistant mutants overproduce phenylalanine. Several lines of evidence suggest that the increased sensitivity to growth inhibition by analogues of phenylalanine and tyrosine reflects a decreased rate of synthesis of aromatic amino acids or their precursors when fructose is the carbon source. This general approach promises to be valuable in the study of regulatory phenomena in microorganisms which, like P. aeruginosa, are naturally resistant to many metabolite analogues.

Pleiotrophy of p-fluorophenylalanine-resistant and antibiotic hypersensitive mutants of Pseudomonas aeruginosa

Mutants ofPseudomonas aeruginosaisolated as being resistant top-fluorophenylalanine (FPA-r) are pleiotropic, showing patterns of phenotypic alteration of host-controlled modification, growth rate at 37 and 43 °C, ability to grow on minimal medium, response to antibiotics and ribosomal characteristics. Alterations in host-controlled modification are also found in FPA-r mutants ofEscherichia coliB.

The pleiotropy arising in these FPA-r mutants ofP. aeruginosaappears to result from alterations in the specificity of protein synthesis. Phenotypic variations in host-controlled modification of the type found in the FPA-r mutants may provide a method for the detection of suppressor mutations which act by miscoding.

Control of pyrimidine biosynthesis in Pseudomonas aeruginosa

The pathway of pyrimidine biosynthesis in Pseudomonas aeruginosa has been shown to be the same as in other bacteria. Twenty-seven mutants requiring uracil for growth were isolated and the mutant lesions were identified. Mutants lacking either dihydroorotic acid dehydrogenase, orotidine monophosphate pyrophosphorylase, orotidine monophosphate decarboxylase, or aspartic transcarbamylase were isolated; none lacking dihydroorotase were found. By using transduction and conjugation, four genes affecting pyrimidine biosynthetic enzymes have been identified and shown to be unlinked to each other. The linkage of pyrB to met-28 and ilv-2 was shown by contransduction. Repression by uracil alone or by broth could not be demonstrated for any enzymes of this pathway, in contrast to the situation in Escherichia coli and Serratia marcescens. In addition, derepression of these enzymes could not be demonstrated. A low level of feedback inhibition of aspartic transcarbamylase was found to occur. It is suggested that the control of such constitutive biosynthetic enzymes in P. aeruginosa may be related to the comprehensive metabolic activities of this organism.

Genetic control of DNA specificity in Pseudomonas aeruginosa

Genotypic and phenotypic changes of HCM inP. aeruginosaare due to a variety of causes. In addition to interstrain genetic differences and the semi-permanent effects of growth at 43°C, mutations affecting both restriction and modification have been isolated by direct selection and through the pleiotropic effects ofp–fluorophenylalanine resistance mutations. It is suggested that some of these changes affecting HCM may be taking place through alterations of the ribosomes.

Enzymes of the tryptophan synthetic pathway in Pseudomonas putida

The first four enzymatic activities of the tryptophan synthetic pathway in Pseudomonas putida were found on separate molecules. Gel filtration and density gradient centrifugation experiments did not disclose any associations or aggregations among them. These findings contrast with the situation found in the enteric bacteria, where the first two activities are found in an aggregate and the third and fourth are catalyzed by a single enzyme. Tryptophan synthetase, the last enzyme of the pathway, consists of two dissociable components. The affinity of these components is less in P. putida than is the case in Escherichia coli.