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At least 19 recordsLinked to original sources
PubMed1979

The nature of arginine auxotrophy in cutaneous populations of staphylococci.

L-Arginine was required for growth by a high percentage of strains of Staphylococcus species that were niche-specific and/or host-specific, but was usually not required for growth by species showing a wide host range. Growth stimulation patterns with arginine intermediates indicated that most of the auxotrophic strains had blocks in an early step(s) in arginine biosynthesis. These strains were designated phenotypically as Arg(CHG) according to the Salmonella typhimurium classification scheme. Staphylococcus simulans strains appeared to be either ArgA or Arg I. The ArgI strains of S. simulans and S. capitis had moderate to high ornithine carbamoyltransferase (EC 2.1.3.3) activities and therefore could not be designated as argI mutants. ArgI strains in other species had no or very low ornithine carbamoyltransferase activities. All of the natural Staphylococcus auxotrophs tested grew in the presence of L-citrulline and had moderate to high argininosuccinase (EC 4.3.2.1) activities. Arginine auxotrophs of species with a wide host range were often capable of reverting to arginine-independent or complete prototrophic growth, whereas auxotrophs of species that tended to be niche-specific and/or host-specific were incapable of reversion to arginine-independence, even in the presence of various mutagens. A relationship between the nature of arginine auxotrophy and habitat is suggested.

Arginine↗
PubMed1976

Sulfur amino acid auxotrophy in Micrococcus species isolated from human skin.

Since methionine and (or) cysteine are required by a large percentage of natural auxotrophic Micrococcus strains isolated from human skin, investigations were directed to determine the specific enzymes affected in sulfur amino acid biosynthesis. Known intermediates in the interrelated cysteine and methionine biosynthetic pathways were tested as growth stimulants. Based on these growth studies, sulfur amino acid auxotrophs were grouped into three cysteine classes and five methionine classes. Selected auxotrophs of M. luteus had deficiencies in ATP sulfurylase (EC 2.7.7.4) and adenosine-5-sulfatophosphate (APS) kinase (EC 2.7.1.25), sulfite reductase (EC 1.8.1.2), serine transacetylase (EC 2.3.1.30), or beta-cystathionase (EC 4.4.1.8) activity; auxotrophs of M. lylae had deficiencies in sulfite reductase and serine transacetylase, beta-cystathionase, or N5, N10-methyltetrahydrofolate reductase (EC 1.1.1.68) activity; all auxotrophs of M. sedentarius tested had deficiencies in N5,N10-methyltetrahydrofolate reductase activity; auxotrophs of M. nishinomiyaensis had deficiencies in adenosine-3-phosphate-5-sulfatophosphate (PAPS) reductase, sulfite reductase, serine transacetylase, or N5,N10-methyltetrahydrofolate reductase activity; auxotrophs of M. varians had deficiencies in APS kinase, PAPS reductase, sulfite reductase, homoserine omicron-transsuccinylase, beta-cystathionase, or N5,N10-methyltetrahydrofolate reductase activity; auxotrophs of M. kristinae had deficiencies in serine transacetylase or cystathionine-gamma-synthase (EC 4.2.99.9) activity; auxotrophs of M. roseus had deficiencies in PAPS reductase, sulfite reductase, or serine transacetylase activity. Results of studies with various mutagens suggested that sulfur amino acid auxotrophy was primarily the result of a single base substitution in usually one or two of the genes controlling biosynthesis. A preliminary study of the amino acid composition of sweat suggested that this important source of nutrients does not contain adequate amounts of cysteine for the growth of cysteine auxotrophs but contains methionine that may be utilized in place of cysteine.

Acetyltransferases↗
PubMed1979

The molecular basis of leucine auxotrophy of quinone-treated Escherichia coli. Active site-directed modification of leucyl-tRNA synthetase by 6-amino-7-chloro-5,8-dioxoquinoline.

Leucyl-tRNA synthetase from Escherichia coli is rapidly inactivated by 6-amino-7-chloro-5,8-dioxoquinoline (quinone), a model substance for cytostatic quinones. Loss of activity follows pseudo-first order kinetics. The quinone masks essential--SH groups that are reactive with N-ethylmaleimide. Specific protection of the enzyme by leucine provides evidence for active site-directed modification. Half-maximal protection is found at a concentration of 150 micron which is identical with the dissociation constant of the enzyme.substrate complex. The competitive inhibitor leucinol also protects the enzyme from inactivation by the quinone. MgATP enhances the protective effect of leucinol about 250-fold, thus substantiating recently published findings on synergistic coupling of ligands to aminoacyl-tRNA synthetases. The results support the assumption that the bacteriostatic quinone directly interferes with leucyl-tRNA synthetase in growing cells. Active-site-directed inhibition of the enzyme could adequately explain the phenotypically observed auxotrophy for leucine of quinone-treated E. coli.

Adenosine Triphosphate↗
PubMed1978

[Induction of auxotrophy in the brucellosis microbe under the effect of N-methyl-N'-nitro-N-nitrosoguannidine].

Mutagenic activity of N-methyl-N'-nitro-N-nitrosoguanidine with respect to Brucella melitensis was studied. In the course of this study the method of obtaining auxotrophic brucella mutants was elaborated. Numerous assortiment of auxotrophic mutants of different types was obtained. In a number of cases the acquisition of auxotrophy was accompanied by profound changes of the strain, such as the changes in morphology of colonies, in the biochemical activity, in the capacity of agglutination and in the virulence.

Brucella↗
PubMed1979

Resistance to 5-fluoroorotic acid and pyrimidine auxotrophy: a new bidirectional selective system for mammalian cells.

We have isolated a clone of murine erythroleukemic cells which will yield a population when a single cell is suspended in a medium composed of dialyzed sera and small molecules. We report that it is feasible--in one experiment--to screen more than 10 of these cells for growth under selective media containing 10(-4) M 5-fluoroorotic acid and 10(-4) M uridine. Cells capable of sustained growth in such media were eventually recovered. Clones of these cells, unlike clones of the parental population, required uridine for growth and contained only 0.39% as much orotate phosphoribosyltransferase, less than 0.5% as much 5-fluoroorotate phosphoribosyltransferase, and 0.013% as much orotidine-5'-monophosphate decarboxylase activity as the parental clones. The parental and variant clones had similar levels of activity for six other enzymes that participate in pyrimidine metabolism.

Animals↗
PubMed1979

Rho and ribosome mutation interaction: lethality of rho-15 in rpsL or rpsE strains, and rho-15 methionine auxotrophy in rps+ strains of Escherichia coli.

The phenotype of Escherichia coli K-12 carrying rho-15 in the genetic background DW319 ilv lacZ::IS1 is described. Seventy-eight percent (70/90) of Ilv+ transductants acquired the following phenotype: temperature-sensitive growth on minimal salts medium, Ts+ growth on complex medium and suppression of the lac polar mutation. At 42 degrees on minimal medium, the rho-15 transductants were cross-fed by a substance diffusing from Rho+ transductants or controls. The requirement for this substance was satisfied by methionine or cystathionine, but not by any other single amino acid or combination of amino acids, by spermidine, or by mono- or divalent cationic salts.--Transduction of rho-15 into four other Ilv- recipients revealed two phenotypic patterns. Recipients with rpsL or rpsE ribosomes yielded rho-15 transductants that were Ts on all media, or Ts on minimal medium whether or not methionine was present. The effect of the ribosome on expression of rho-15 was confirmed by transduction of appropriate rps alleles into DW319, followed by co-transduction of rho-15 with Ilv+. The growth rate of double rho-15 rpsL or rho-15 rpsE strains was severely reduced at 42 degrees in comparison with strains carrying any of these single mutations. Models for rho and ribosome interaction are presented.

Culture Media↗
PubMed1979

Synthesis and activation of asparagine in asparagine auxotrophs of Saccharomyces cerevisiae.

L-Asparagine synthesis in Saccharomyces cerevisiae is performed by a glutamine-dependent asparagine synthetase of the type found in higher organisms. Auxotrophy for asparagine has been obtained in two classes of mutants. In class I, asparagine synthetase activity is cancelled. These mutants combine two mutations, asnA- and asnB-. Neither asnA- nor asnB- mutation alone leads to total auxotrophy. Partial auxotrophy as well as a strong decrease in enzyme activity result from asnA- mutation. No change is detectable in cells with the asnB- mutationalone. This, and Jones' report [J. Bacteriol. 134, 200-207 (1978)] of auxotrophy resulting from the combination of two mutations, are strong supports for asparagine synthesis being an unusual biosynthetic operation. In class II, auxotrophy results from a single mutation which leads to a modification of the efficiency of the asparaginyl-tRNA synthetase (asnRS- mutation). This auxotrophy is cancelled if asparaginase I activity (the only one present in sigma 1278b wild type) is cancelled by casnI- mutation. This latter mutation allows an increase in the asparagine pool which is able to compensate for the asparaginyl-tRNA synthetase partial defect of the asnRS- mutant.

Amino Acyl-tRNA Synthetases↗
PubMed2026

The Evolutionary Maintenance of Amino Acid Prototrophy in Escherichia coli.

Escherichia coli is a prototroph and can synthesize all twenty proteinogenic amino acids when required to grow in minimal medium. There are approximately sixty protein-coding genes individually essential for amino acid synthesis. This is a large mutational target for the accumulation of detrimental mutations. E. coli can rewire biosynthetic pathways in response to mutational damage, but the limits of this capacity are poorly understood. Here, to address evolutionary robustness, we asked whether and how the phenotypes of irreversible mutations causing auxotrophy could be suppressed or bypassed in the absence of horizontal gene transfer (HGT). Spontaneous suppressors could be selected for only ten of fifty-nine mutants tested (detection limit ∼7 × 10-11). Mechanisms of suppression included regional amplifications, mutations increasing gene or operon expression, mutations relaxing enzyme specificity, and mutations causing biochemical pathway diversions. Overall, the data show that spontaneous suppression of auxotrophy caused by an irreversible mutation is an evolutionary survival mechanism relevant only to a minority of the genes essential for amino acid synthesis. As a consequence, the essential genetic foundations for amino acid prototrophy are expected to be degraded over time by mutations (Muller's ratchet) and metabolic rewiring alone will be insufficient to counteract this effect. This implies that maintaining phenotypes, including prototrophy in E. coli, and potentially other bacterial species, is likely to be reliant on HGT of housekeeping genes to counteract the effects of inevitable mutational inactivation. Accordingly, chromosomal HGT in bacteria may be critical for survival across diverse environmental niches.

Escherichia coli↗
PubMed1977

Some genetical aspects of ornithine metabolism in Aspergillus nidulans.

A possible minor route of ornithine catabolism in Aspergillus nidulans might begin with the ornithine decarboxylase reaction and end with the succinic semialdehyde dehydrogenase reaction. It is therefore of interest that the putative structural genes for these two enzymes, puA and ssuA, respectively, are tightly linked group II. However, this linkage is unlikely to have regulatory significance because ileA, the structural gene for threonine dehydratase, separates them. The gene order in this region is ssuA-ileA-puA-mauB-anB. (mauB- mutations result in loss of monoamine oxidase whilst anB- mutations lead to aneurin auxotrophy.) 2. An auxotrophy for ornithine or putrescine in A. nidulans occurs in double mutants lacking arginase and blocked before ornithine in the arginine biosynthetic pathway. Some residual ornithine synthesis in such double mutants can be catalysed by ornithine delta-transaminase, especially if it is synthesised constitutively.

Aspergillus nidulans↗
PubMed1975

Inhibition of leucyl-tRNA synthetase in Escherichia coli by the cytostatic 5,8-dioxo-6-amino-7-chloroquinoline.

At concentrations of 1-1.6 mug/ml, 5,8-dioxo-6-amino-7-chloroquinoline causes auxotrophy for leucine in Escherichia coli MRE 600. With increasing concentrations of this quinone additional amino acids are required for growth. The amount of leucine in the pool of free amino acids is not decreased after treatment of E. coli with the quinone. Transfer RNALeu, however, is charged with leucine less than 10% in quinone-treated cells of E. coli, whereas in control cells the degree of aminoacylation is about 85%. From these data we conclude that the quinone causes auxotrophy for leucine by interacting with the charging process of tRNALeu. Quinone was found to inhibit leucyl-tRNA synthetase activity in purified extracts of E. coli with E. coli tRNA as substrate.

Amino Acids↗
PubMed1977

Characterization of Salmonella typhimurium mutants with altered glutamine synthetase activity.

A number of glutamine auxotrophs of Salmonella typhimurium were isolated and characterized genetically. Three of the mutations appear to be closely linked and are complemented by episomes carrying the glnA region of Escherichia coli. The lesions in these strains are approximately 20% linked by P1 transduction with a mutation in the rha gene, but are unlinked to ilv. Another mutation causing glutamine auxotrophy in strain JB674 is genetically distinct from the others. Strain JB674 grown in glucose medium containing ammonia as the nitrogen source has reduced levels of glutamine synthetase that is more adenylylated than in the parent strain, suggesting that the enzyme can not be deadenylylated normally. The lesion causing glutamine auxotrophy in JB674 lies in the region corresponding to the glnB and glnE genes affecting glutamine synthetase modification in Klebsiella areogenes. Four Gln+ revertants of JB674 have glutamine synthetase activities 4 to 6 fold higher than normal. One mutation causing this increased enzyme synthesis has been shown by three-factor crosses with the glnA mutations to lie near or within the glnA gene.

Chromosome Mapping↗
PubMed1979

Induction of mutation in Escherichia coli by freeze-drying.

The effect of freeze-drying on phenotypic reversion of amino acid auxotrophy to prototrophy was studied in Escherichia coli. In a radioresistant strain, E. coli H/r 30 (uvr+ exr+), which can repair the deoxyribonucleic acid damaged due to freeze-drying, an increased mutation frequency from auxotrophy to prototrophy was observed with increased time of freeze-drying of the cells. On the other hand, in a radiosensitive strain, E. coli NG 30 (recA), which cannot repair the damaged deoxyribonucleic acid due to a lack of repair enzyme system, no significant reversion occurred, although the survival rate was very low. The rate of phenotypic reversion dut to freeze-drying in both E. coli RIMD 0509109 (uvr+ exr+) and RIMD 0509115 (uvr exr+) was almost the same, indicating that the phenomenon is independent of the uvr character. From these results it is concluded that mutation was induced in E. coli cells during the rehydration when the damaged deoxyribonucleic acid was repaired by exr character of the cells. Thus, we propose that a serious consideration should be paid to the freeze-drying technique to preserve bacterial cells.

Arginine↗
PubMed1978

[Rhodosporidium Banno: dose-effect relations, mutagenic efficiency, and spectrum of mutants in the induction of auxotrophic mutants by ultraviolet light and N-methyl-N'-nitro-N-nitrosoguanidine].

The kinetics, efficiency, and specificity of induction of forward mutations to auxotrophy by ultraviolet light (UV) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined in stationary phase cells of Rhodosporidium (Rhodotorula) wild strain Rg1. In comparison to the spontaneous level the frequency of auxotrophic mutants was increased more than 1000 times by both mutagens, however, the mutagenic efficiency of MNNG was higher than that of UV. We found that the forward mutation rate is a linear function of the applicated UV and MNNG doses in the range to 600 J m-2 or 25 mM X min, respectively. The 35 studied biosynthetic pathways to amino acids, purines, pyrimidines, and vitamins are genetically blocked at different frequencies, but there is not any significant difference between UV and MNNG induced frequencies of mutants with a specific requirement. However, in difference to the approximately equal distribution of the MNNG-induced nic mutants among the genetic blocks of the tryptophan-nicotinamide pathway, UV-induced nic mutants occurred with a higher frequency in the genes of the tryptophan pyrrolase and the 3-hydroxykynureninase than in the genes of the other enzymes of the pathway.

Amino Acids↗
PubMed2026

Characterization of carABpyrB operon and role of pyrE in Francisella novicida biofilm.

Pyrimidine biosynthesis is essential for bacterial growth, but its role in regulating biofilm formation in Francisella (F.) novicida remains poorly defined. In this study, we experimentally defined the carABpyrB operon in F. novicida and investigated how disruption of the de novo pyrimidine biosynthesis pathway affects growth and biofilm formation under nutrient-restricted conditions. Reverse transcriptase PCR confirmed co-transcription of carA, carB, and pyrB, and promoter prediction identified two putative σ70-dependent promoter regions upstream of carA. Transposon mutants disrupted in carA, carB, and pyrB exhibited pronounced growth defects in Chamberlain's Defined Medium that were restored by uracil supplementation, confirming pyrimidine auxotrophy and functional disruption of de novo pyrimidine biosynthesis. We then extended this analysis to additional genes in the pyrimidine biosynthetic pathway and assessed biofilm formation in modified Mueller-Hinton broth, a nutrient-restricted condition. In this medium, carA, carB, pyrB, and pyrE mutants exhibited growth deficiencies; however, the pyrE mutant uniquely produced significantly more biofilm than the wild type. This phenotype remained evident even without growth normalization, with the pyrE mutant producing 3.3-fold more biofilm than wild type, despite impaired growth, and increased to 11.8-fold when normalized to growth. Quantitative PCR demonstrated that uracil supplementation represses carA, carB, and pyrB transcription, consistent with feedback regulation of the pathway. Together, these findings indicate that pyrimidine limitation is not simply a growth-limiting condition but can alter biofilm regulation, with pyrE disruption revealing a strong association between de novo pyrimidine biosynthesis and biofilm formation.

Biofilms↗