Showing papers on "Mutant published in 1971"

Clock Mutants of Drosophila melanogaster

Abstract: Three mutants have been isolated in which the normal 24-hour rhythm is drastically changed. One mutant is arrhythmic; another has a period of 19 hr; a third has a period of 28 hr. Both the eclosion rhythm of a population and the locomotor activity of individual flies are affected. All these mutations appear to involve the same functional gene on the X chromosome.

Potassium Transport Loci in Escherichia coli K-12

Abstract: Mutants of Escherichia coli K-12 requiring considerably elevated concentrations of potassium for growth are readily obtained as double mutants combining a kdp mutation with a mutation in one or more of five other loci. These loci are referred to as trk, for transport of K, because these mutations result in alterations in K transport. The kdp mutation is essential in the isolation and identification of this type of mutant; in a Kdp(+) strain, the presence of a trk mutation does not prevent growth of the strain in media containing very low concentrations of K. The trk loci are widely scattered over the E. coli chromosome; none of them is very near any other trk locus or near the kdp genes.

Beginning a Genetic Analysis of Conjugational Transfer Determined by the F Factor in Escherichia coli by Isolation and Characterization of Transfer-Deficient Mutants

Abstract: Eighty-four transfer-deficient mutants of Flac have been isolated; 27 of these bear amber mutations and 1 mutant is temperature-sensitive. All the mutants transfer between 10(-2) and <10(-5)% as well as wild-type Flac, all are curable by acridine orange treatment, and all are resistant to the female-specific phage phi(II). Some of the mutants are partially sensitive to female-specific phage tau. Sixty-three of the mutants are resistant to the male-specific phages f1, f2, and Qbeta; 15 are resistant only to f2; and 6 are sensitive to all three male-specific phages. Most of the mutants are still poor recipients in conjugation, but four of the mutants resistant to f1, f2, and Qbeta have become good recipients. Those mutants resistant to all three male-specific phages do not seem to make F-pili.

Beginning a Genetic Analysis ofConjugational Transfer Determined bytheFFactorin Escherichia coli byIsolation andCharacterization ofTransfer-Deficie nt Mutants

Abstract: Eighty-four transfer-deficient mutants of Flac have been isolated; 27 of these bear amber mutations and 1 mutant is temperature-sensitive. All the mutants transfer between 10−2 and <10−5% as well as wild-type Flac, all are curable by acridine orange treatment, and all are resistant to the female-specific phage φII. Some of the mutants are partially sensitive to female-specific phage tau. Sixty-three of the mutants are resistant to the male-specific phages f1, f2, and Qβ; 15 are resistant only to f2; and 6 are sensitive to all three male-specific phages. Most of the mutants are still poor recipients in conjugation, but four of the mutants resistant to f1, f2, and Qβ have become good recipients. Those mutants resistant to all three male-specific phages do not seem to make F-pili.

Mutants of yeast defective in mutation induced by ultraviolet light.

Abstract: NDUCED mutations are thought to arise as a result of enzymatic processes uti‘lizing DNA damage as a substrate (BRIDGES 1969). Although the molecular mechanism is not known, evidence reviewed by WITKIN (1969) suggests that in E. coli mutations are produced during postreplication repair of lethal damage induced by ultraviolet light (UV) and controlled by r e d and ezrf (or lexf) genes. Strains carrying rec or ezr, although normal in excision repair, exhibit reduced or no UV mutability compared to wild type. In addition, such strains are UV sensitive, X-ray sensitive, and recombination deficient in varying degrees ( WITKIN 1969). In previous studies of UV-induced mutation in fungi, UV-sensitive strains have been selected on the assumption that UV mutagenesis might be related to dark repair of lethal damage. In some of these UV-sensitive strains, the frequencies of UV mutation are reduced compared to wild type at equal UV doses (CHANG, LENNOX and TUVESON 1968; NASIM 1968; WOHLRAB and TUVESON 1969). whereas in others these frequencies are enhanced (AVERBECK et al. 1970; RESNICK 1969; ZAKHAROV, KOZINA and FEDOROVA, 1970). To identify new genes controlling UV-induced mutation, it is desirable to select strains directly for defective mutation induction, thereby avoiding the prior condition that all such mutants be UV-sensitive. Mutants of Saccharomyces cereuisiae were selected ( LEMONTT and MORTIMER 1970) for reduced ability to undergo UV-induced locus reversion of the ochresuppressible (GILMORE 1967; HAWTHORNE 1969) argl-17 allele. This paper describes the isolation and some characteristics of these “reversionless” mutants, The results are discussed in relation to current ideas about induced mutagenesis.

Non-Mendelian Mutation Allowing Ureidosuccinic Acid Uptake in Yeast

Abstract: Mutants of Saccharomyces cerevisiae capable of growth on a minimal medium supplemented with ureidosuccinic and glutamic acids have been isolated from a pyrimidineless strain. One of these mutants consistently yielded a non-Mendelian meiotic segregation. Moreover, the mitotic transmission of the mutation was very high. It is suggested that the mutation is nonchromosomal and could be mitochondrial. However, this mutation behaves very differently from other mitochondrial mutations.

Oxidative phosphorylation in Escherichia coli K 12. Mutations affecting magnesium ion- or calcium ion-stimulated adenosine triphosphatase

Abstract: 1. Two mutants of Escherichia coli K 12 were isolated which, although able to grow on glucose, are unable to grow with succinate or d-lactate as the sole source of carbon. 2. Genetic mapping of these mutants showed that they both contain a mutation in a gene (designated uncA) mapping at about minute 73.5 on the E. coli chromosome. 3. The uncA− alleles were transferred by bacteriophage-mediated transduction into another strain of E. coli and the transductants compared with the parent strain to determine the nature of the biochemical lesion in the mutants. 4. The mutants gave low aerobic growth yields when grown on limiting concentrations of glucose, but oxidase activities in membranes from both the mutants and the normal strain were similar. 5. Measurement of P/O ratios with d-lactate as substrate indicated that a mutation in the uncA gene causes uncoupling of phosphorylation associated with electron transport. 6. Determination of the Mg2+,Ca2+-stimulated adenosine triphosphatase activities in the mutant and normal strains indicated that the uncA gene is probably the structural gene for Mg2+,Ca2+-stimulated adenosine triphosphatase. 7. Mg2+,Ca2+-stimulated adenosine triphosphatase therefore appears to be essential for oxidative phosphorylation in E. coli.

Genetical and structural analyses of cell-wall formation in Chlamydomonas reinhardi

Abstract: Fifteen mutant strains of Chlamydomonas reinhardi were isolated which showed defects in some aspect of the process of cell-wall formation. Genetic analyses indicated that most of the mutations were due to single gene changes; two were anomalous in that non-Mendelian segregations were obtained on crossing with other genotypes, and on selfing they frequently gave rise to wild-type phenotypes.Occasional somatic revertants were also obtained from these two strains. On the basis of these analyses it is suggested that there are two levels of control operating in the process of cell wall biogenesis - one concerned with subunit production at the nuclear level and another, possibly concerned with three-dimensional organization, at another level. Electron-microscope analyses of the different mutants showed the mutants to be divided into three main categories: those in which the wall was formed but was not attached to the plasma membrane, those in which the wall was attached to the membrane, and those in which very little wall was formed. In the last class in particular, vesicles containing wall precursors were clearly visible, and were shed through the plasma membrane into the medium.

Classification and mapping of spontaneous and induced mutations in the histidine operon of Salmonella.

Abstract: Publisher Summary This chapter reviews that over 1500 histidine-requiring mutants of independent origin have been mapped in the histidine operon of S. typhimurium. About 1,000 mutants have been characterized as type of mutation. The type of mutation has been determined for each mutant by the collective results of recombination tests, analysis of the pattern of spontaneous, N-methyl-N-nitro-N-nitrosoguanidine, and acridine half-mustard induced reversion, and the presence of suppressors among revertants. It also discusses that the type of mutation is correlated with polarity in the operon, presence of immunologically detectable cross-reacting protein, complementation, and genetic map position. The spectrum of spontaneously occurring histidine-requiring mutants is compared with those found after treatment of bacteria with a number of widely used mutagens.

A method for detection of phage mutants with altered transducing ability.

Abstract: A method is described which allows the detection of phage mutants with increased or decreased transduction frequencies. Some properties of such mutants are presented.

The Role of Recombination in Growth of Bacteriophage Lambda I. The Gamma Gene

Abstract: Although recombination in microorganisms has been studied extensively, the role of recombination in growth is not entirely understood. For example, it is not yet clear to what extent recombination proteins are involved in events such as repair or synthesis of DNA. One way to approach the problem is to study the effect on growth of a deficiency in recombination. Recombination-deficient mutants have been isolated in several systems. In E. coli (Howard-Flanders and Theriot, 1966; Clark, 1967) they define three cistrons recA, B, and C, of which B and C determine an exonuclease (Barbour and Clark, 1970). None of the three cistrons appears to be essential for cell growth, since the mutants are viable. (However, since the selection procedure scored only viable cells, these mutants might retain a low but essential level of the gene products.) Recombination-deficient mutants have also been isolated in several bacteriophages. In phage P22, these mutants ( erf − ) grow in rec + but not in rec − hosts, suggesting that recombination proteins are essential for growth in P22 (Botstein and Matz, 1970). In phage T4, mutations in several essential cistrons seem to affect recombination (Bernstein, 1968). In phage λ, recombination-deficient mutants ( red − , Signer and Weil, 1968; Echols and Gingery, 1968) define two genes (Shulman et al., 1970), namely exo (exonuclease, Korn and Weissbach, 1963) and β (beta protein, Radding and Schreffler, 1966). In this phage neither gene appears to be essential for growth, since both exo − mutants (including deletion mutants) and β − mutants (including amber mutants) make plaques on rec − ...

On the rate of molecular evolution

Abstract: There are at least two outstanding features that characterize the rate of evolution at the molecular level as compared with that at the phenotypic level. They are; (1) remarkable uniformity for each molecule, and (2) very high overall rate when extrapolated to the whole DNA content. The population dynamics for the rate of mutant substitution was developed, and it was shown that if mutant substitutions in the population are carried out mainly by natural selection, the rate of substitution is given byk = 4 N e s 1 v, whereN e is the effective population number,s 1 is the selective advantage of the mutants, andv is the mutation rate per gamete for such advantageous mutants (assuming that 4N e s 1 ≫ 1). On the other hand, if the substitutions are mainly carried out by random fixation of selectively neutral or nearly neutral mutants, we havek = v, wherev is the mutation rate per gamete for such mutants. Reasons were presented for the view that evolutionary change of amino acids in proteins has been mainly caused by random fixation of neutral mutants rather than by natural selection. It was concluded that if this view is correct, we should expect that genes of “living fossils” have undergone almost as many DNA base replacements as the corresponding genes of more rapidly evolving species.

Escherichia coli Mutants Blocked in Lambda DNA Synthesis

Abstract: Both phage and bacterial genes are essential for replication of phage λ DNA. Lambda genes O and P are essential for phage DNA replication; mutants defective in either gene are able to replicate less than one round of DNA (Joyner et al., 1966; Ogawa and Tomizawa, 1968). It has been suggested that genes O and P code for an endonucleolytic activity that acts on λ DNA (Shuster and Weissbach, 1969; E. Jordan, personal communication). It is quite clear that λ replication requires in addition some host DNA synthesis functions, since λ is unable to grow in certain Escherichia coli mutants containing temperature-sensitive defects in DNA synthesis (Hirota et al., 1968; Kohiyama, 1968). In particular, Fangman and Feiss (1969) have reported that λ is unable to replicate at high temperature in a temperature-sensitive mutant of E. coli, FA22, which is defective in host DNA synthesis at 39°C. Here we report the isolation and preliminary characterization of a class of E. coli mutants, called groP − , which are unable to propagate lambdoid phages. Evidence is presented (1) that the block in phage λ development is due to inability of the gene P product to function, and (2) that the groP − bacteria are themselves conditionally defective in DNA synthesis. These results suggest that there is a functional association between the gene P product of phage λ and the host DNA synthesis system. RESULTS AND DISCUSSION Growth of lambdoid phages in bacterial mutants Bacterial mutants ( groP − ) unable to support growth of λ and 434 were...

Natural Read-through at the UGA Termination Signal of Qβ Coat Protein Cistron

Abstract: GENETIC analysis of conditional lethal mutants of Qβ, a small RNA-containing bacteriophage of Escherichia coli, has demonstrated the existence of three cistrons1. These have been correlated2 with three of the four phage-specific proteins observed after Qβ infection2–4: gene 1 codes for the phage-specific subunit of Qβ replicase, gene 2 for the maturation protein and gene 3 for the major coat protein. Using SDS-polyacrylamide gel electrophoresis to characterize these polypeptides, Garwes et al. introduced the nomenclature I, IIa and III for the phage-specific proteins3; the corresponding molecular weights are 64,000, 41,000 and 14,000.

Functional Organization of Genetic Material as a Product of Molecular Evolution

Abstract: MOLECULAR evolution consists of a sequence of events in which originally rare molecular mutants (DNA changes) spread into the species. Two important classes of mutations are nucleotide (or amino-acid) replacement and gene duplication.

Normal and mutant glycine transfer RNAs.

Abstract: THE glycine-specific tRNAs of E. coli can be grouped into three subspecies which are separated by chromatography on benzoylated DEAE cellulose (BDC): tRNAGly1 (GGG), tRNAGly2 (GGA/G) and tRNAGly3 (GGU/C)1,2. The tRNAGly1 and tRNAGly2 are specified by the genes, glyU and glyT, respectively, which have been located at 55 and 77 minutes on the E. coli chromosome. Suppressors of tryptophan A gene (trpA) missense mutations and partial diploid strains have been used extensively to characterize the glycine tRNA structural genes (Table 1)1–3. A common property of these suppressor mutations is that the altered tRNAGly is no longer aminoacylated at the normal rate by the glycyl tRNA synthetase (GRS). When ordinary loading conditions are used virtually none of the suppressor tRNA species are amino-acylated. These studies have shown that single gene copies are normally present at the glyT and glyU loci.

The uptake of C4-dicarboxylic acids by Escherichia coli.

Abstract: Escherichia coli inducibly form a system effecting the uptake of a number of C4-dicarboxylic acids; glucose or inhibitors of protein synthesis prevent this induction. After growth on C4-dicarboxylic acids; glucose or inhibitors of protein synthesis prevent this induction. After growth onC4-dicarboxylic acids, washed cells take up such acids rapidly and, initially, linearly with time; the Km for this process is approx. 30 μM and the Vmax is approx. 25 nmoles X min−1 mg dry wt −1, irrespective of the identity of the acid transported. C4-dicarboxylic acids other than fumarate, succinate, malate, aspartate, and maleate, are takep up poorly. Washed cells talking up 14C-labelled C4-dicasrboxylic acids incorporate isotope mainly into macromolecular cell components; no significant intracellular accumulation of C4-acids is observed. Mutants blocked in component reactions of the tricarboxylic acid cycle are also greatly impaired in their ability to take up C4-acids; mutants blocked in reaction ancillary to the cycle are not. It is suggested that E. coli effect the uptake of C4-dicarboxylic acids througha common, inducible and highly specific transport system.

Immunity in Experimental Salmonellosis II. Basis for the Avirulence and Protective Capacity of gal E Mutants of Salmonella typhimurium

Abstract: Salmonella typhimurium strains which are deficient in uridine diphosphate (UDP)-galactose-4-epimerase (gal E mutants) owe their outstanding protective capacity when used as live vaccine to the fact that when galactose is supplied exogenously, such as occurs in vivo, smooth cell wall lipopolysaccharides are synthesized. The mutants lose most of their protective capacity when this phenotypic curing is prevented by a second mutation of the kind found in strains LT2M1A (deficient in galactokinase) or E32 (deficient in UDP-galactose-lipopolysaccharide transferase). Despite such phenotypic reversion, the gal E mutants are rendered avirulent as a result of galactose-induced bacteriolysis. Secondary mutants have been isolated which differ from each other with respect to the extent of galactose-induced lysis. The differences in galactose sensitivity are attributable to different activities of the other Leoloir pathway enzymes, namely, galactokinase and galactose-1-phosphate-uridyl transferase. The influence of these enzymes on lipopolysaccharide composition and galactose sensitivity and thus on virulence and immunogenicity of gal E mutants has been studied.

Bacterial Mutants in Which the Gene N Function of Bacteriophage Lambda Is Blocked Have an Altered RNA Polymerase

Abstract: Bacterial mutants have been isolated, called groN, that block phage development by interference with the action of the product of the phage N gene. lambdatrp phages, which depend on the N product for the synthesis of tryptophan enzymes, do not make these enzymes in groN bacteria. Two type of phage mutants have been isolated that can overcome the groN block. One type makes an altered N product, the other contains an N-bypass mutation. The groN mutation is closely linked to the rifamycin-resistance locus in Escherichia coli. Purified RNA polymerase from the groN mutant is less activated by salt and more sensitive to rifamycin than is the polymerase from gro(+). This suggests that the groN mutation produces a structural change in the bacterial RNA polymerase such that it can no longer interact properly with the phage N product.

Isolation and Characterization of Tricarboxylic Acid Cycle Mutants of Bacillus subtilis

Abstract: A technique was developed for the detection, on agar, of mutants of Bacillus subtilis that lacked a functional tricarboxylic acid cycle. Mutants devoid of detectable levels of aconitase, isocitric dehydrogenase, alpha-ketoglutarate dehydrogenase, succinic dehydrogenase, fumarase, and malate dehydrogenase have been isolated and characterized. Several mutants with conditionally expressible lesions, including a mutant with a heat-sensitive citrate synthase, have also been isolated. All of the mutants examined express all the biochemical markers normally absent in early-stage sporulation mutants except elastase, and some of these mutants sporulated nearly as well as the prototroph.

Adenosine 3′:5′-Cyclic Monophosphate Concentration in the Bacterial Host Regulates the Viral Decision between Lysogeny and Lysis

Abstract: Mutants of Salmonella typhimurium defective in adenylate cyclase (cya gene) or in cAMP receptor protein (crp gene) are lysogenized at reduced frequency by phage P22. One class of the bacterial mutants with an altered RNA polymerase (rif gene) is also lysogenized at reduced frequency. In the three types of mutant bacteria, the phage's decision between lysogeny and lysis is shifted to lysis and the phage form clear plaques. We propose that in wild-type bacteria the cAMP-receptor protein, in combination with cAMP, activates bacterial RNA polymerase to transcribe certain phage genes that are required for efficient lysogenization. Under conditions of strong catabolite repression, when the supply of energy and biosynthetic components is abundant and the concentration of cAMP is low, the phage would multiply and lyse the cell. When the supply of energy is deficient and the concentration of cAMP is high, the phage would lysogenize the cell. Phage mutants have been isolated that form turbid plaques on the three classes of bacterial mutants due to a higher frequency of lysogeny. These phage mutants have been shown by complementation to be defective in the same gene, which we have called the cly gene. These cly mutants lysogenize the wild-type bacteria with a 99% frequency and, thus, do not form plaques on them. Other kinds of bacterial mutants are also lysogenized at reduced frequency by phage P22. They may be altered in other physiological control systems that influence the frequency of lysogenization.