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1.  Kinetic and Genetic Analyses of d-Cycloserine Inhibition and Resistance in Escherichia coli 
Journal of Bacteriology  1965;90(5):1238-1250.
Curtiss, Roy, III (Oak Ridge National Laboratory, Oak Ridge, Tenn.), Leigh J. Charamella, Claire M. Berg, and Paula E. Harris. Kinetic and genetic analyses of d-cycloserine inhibition and resistance in Escherichia coli. J. Bacteriol. 90:1238–1250.1965.—Wild-type cells of Escherichia coli growing at 37 C in mineral salts-glucose medium with vigorous aeration were lysed at maximal exponential rates by 10−4 to 10−2md-cycloserine. At concentrations above 2 × 10−2m, d-cycloserine was bacteriostatic. Low levels of d-cycloserine (10−5m) and pencillin G (10 units per ml) interacted synergistically to cause a rapid exponential rate of lysis. Spontaneous mutations to d-cycloserine resistance occurred in discrete steps at frequencies of 10−6 to 10−7 for each step. First-, second-, and third-step d-cycloserine-resistant mutants were lysed at maximal exponential rates by d-cycloserine concentrations of 10−3, 3 × 10−3, and 5 × 10−3m, respectively. d-Alanine, l-alanine, and dl-alanyl-dl-alanine reversed d-cycloserine-induced lysis, in that order of effectiveness. On the basis of these observations, a d-cycloserine-enrichment cycling technique was developed for isolation of auxotrophic mutants. d-Cycloserine at 2 × 10−3m was as efficient as penicillin G (1,000 units per ml) for mutant enrichment in E. coli and should be useful for isolation of mutants in penicillin-resistant microorganisms. Bacterial conjugation experiments indicated that all three mutations conferring d-cycloserine resistance were linked to the met1 locus. Transduction experiments showed that the mutation conferring first-step resistance was at least 0.5 min away from the mutations conferring second- and third-step resistance. The latter two mutations possibly occurred in the same gene, since they were sometimes carried in the same transducing phage. Studies on expression of d-cycloserine resistance indicated that these mutations were neither dominant nor recessive to each other nor to the d-cycloserine-sensitivity allele. Each allelic state exerted its influence on the phenotype independently of the others. These results are discussed in terms of the known inhibition of alanine racemase and d-alanyl-d-alanine synthetase by d-cycloserine.
PMCID: PMC315808  PMID: 5321479
2.  Inhibition of Amino Acid Transport in Escherichia coli by Some Beta-Lactam Antibiotics 
Among 10 antibiotics tested, cephaloridine and cephalothin showed the greatest inhibition of proline active transport. Ethylenediaminetetraacetate pretreatment of the cells did not enhance inhibition by any of these 10 antibiotics. The inhibition of active transport of 10 additional amino acids by cephaloridine and cephalothin was studied. Both antibiotics inhibited transport of three amino acids which, like proline, have transport systems resistant to osmotic shock; neither antibiotic inhibited transport of the remaining amino acids, including three with shock-resistant and four with shock-sensitive systems.
PMCID: PMC352112  PMID: 327925
3.  Penicillin-Induced Lysis of Escherichia coli in Medium That Does Not Support Sustained Growth 
Exponentially growing cells of an Escherichia coli auxotroph that are washed and resuspended in buffer containing a carbon source undergo sufficient growth to render them susceptible to penicillin-induced lysis, even in the absence of the required metabolite. This lysis is probably responsible for the reduction in intracellular enzyme activity previously attributed to a direct effect of penicillin upon the enzyme.
PMCID: PMC429603  PMID: 773303
4.  Procedure for Isolating Mutants Defective in Metabolite Transport or Utilization 
Journal of Bacteriology  1975;121(3):1216-1218.
Mutants defective in uptake or utilization of a given metabolite can readily be obtained from facultative auxotrophs (for that metabolite) by penicillin enrichment under nonpermissive conditions in the presence of a low level of the required metabolite.
PMCID: PMC246058  PMID: 1090600
5.  Effect of Enrichment Procedure upon Auxotroph Recovery in Escherichia coli K-12 
Proline-requiring auxotrophs are recovered preferentially after mutant enrichment procedures (e.g., penicillin) which perturb the cell envelope, but not after procedures (e.g., thymineless death) which affect other cellular targets. This probably stems from effects of penicillin and similar antibiotics upon proline metabolic and transport enzymes associated with the cell envelope.
PMCID: PMC429082  PMID: 1094942
6.  Proline Excretion and Indirect Suppression in Escherichia coli and Salmonella typhimurium 
Journal of Bacteriology  1974;118(3):928-934.
The last step in proline biosynthesis in Escherichia coli K-12, Salmonella typhimurium LT7, and a number of other enterobacterial isolates is regulated so that no proline is excreted, even if excess Δ1-pyrroline-5-carboxylate, the immediate precursor of proline, is added to a culture. In proline auxotrophs blocked at an early step in proline biosynthesis (proA or proB), reversion to prototrophy is often due to a mutation in the arginine pathway which diverts N-acetyl glutamate γ-semialdehyde to proline synthesis, thus bypassing the proA or proB block. In such double mutants (proAB, argD), the last step in proline synthesis appears to be unregulated, since proline is excreted. Feedback inhibition and repression of the arginine pathway overcomes indirect suppression (restoring the Pro− phenotype), but proline regulation is not restored; double mutants still excrete proline when fed Δ1-pyrroline-5-carboxylate exogeneously. A new class of proline analogue-resistant mutant, due to mutation at argD, is also described.
PMCID: PMC246841  PMID: 4598010
7.  Thymineless Death in polA+ and polA− Strains of Escherichia coli 
Journal of Bacteriology  1973;115(2):707-708.
The extreme sensitivity of polA− cells to thymineless death is due, primarily, to the absence of an extended lag prior to the commencement of death. Once thymineless death has commenced, the rate in polA− cells is only slightly faster than in polA+ cells.
PMCID: PMC246303  PMID: 4579878
8.  Auxotroph Accumulation in Deoxyribonucleic Acid Polymeraseless Strains of Escherichia coli K-121 
Journal of Bacteriology  1971;106(3):797-801.
Spontaneous auxotrophs are found with high frequency in several strains of Escherichia coli K-12 deficient in Kornberg deoxyribonucleic acid polymerase. These include amino acid-, vitamin-, purine-, and pyrimidine-requiring strains. Although this was suggestive evidence that these strains might be mutators, reconstruction experiments demonstrate that auxotrophs possess a selective advantage over prototrophs in the same culture. Thus, despite the high frequency of auxotrophs in polymerase-deficient strains, it is not yet clear whether they have elevated mutation rates.
PMCID: PMC248694  PMID: 4934065
9.  Differential Recovery of Auxotrophs After Penicillin Enrichment in Escherichia coli 
Journal of Bacteriology  1971;106(2):297-300.
Various auxotrophs are recovered from a penicillin enrichment cycle with differing efficiencies. Reconstruction experiments indicate that, under starvation conditions in the presence of penicillin, most auxotrophs undergo some death, whereas prolineless mutants are virtually immune to penicillin-induced killing.
PMCID: PMC285095  PMID: 4929854

Results 1-9 (9)