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1.
Summary Acetateless mutants of Escherichia coli K 12 lacking the enzymatic activities either of the carboxylase, the lipoic reductase-transacetylase or of all components of the pyruvate dehydrogenase complex are shown to be the consequence of mutations in the closely linked structural genes for the constituent enzymes of the enzyme complex. This genetic segment (the acetate locus = Ac) was found on the E. coli chromosome between the leucine and T R loci. Acetate and leucine loci are transduced jointly by the phage Plkc. The preparation is described of double mutants carrying two genetic lesions in the pyruvate dehydrogenase structural gene cluster. The mutant sites of 0 0-type strains have been localized in a part of the carboxylase structural gene corresponding to the left extremity (nearest the leucine locus) of the acetate locus.Studies on possible genetic relationships between the pyruvate and -ketoglutarate dehydrogenases (which regarding the individual reactions catalyzed are very similar and partly identical) revealed that the two -keto acid dehydrogenases most likely do not share any genetic determinant.
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2.
Summary Two classes of partial revertants of 0 0-type mutants in the pyruvate dehydrogenase system of Escherichia coli K 12 could be distinguished enzymatically and genetically. In one class of these strains the second mutation has occurred at or near the primary 0 0 site. The partial revertants of this class synthesize a pyruvate dehydrogenase complex containing a defective carboxylase component. The strains of the other class proved to be suppressed 0 0-type mutants,the second mutation having occurred outside the acetate locus on the E. coli chromosome. One of the suppressor alleles was found to be specific for a certain 0 0 site; it did not act on another genetically distinguishable 0 0 site nor on any of the tested mutant sites in the pyruvate dehydrogenase genes. The suppressed 0 0 type strains synthesize only small amounts (about 1/50 of wild type) of pyruvate dehydrogenase with a carboxylase component which so far could not be distinguished from the wild type carboxylase. In addition, the suppressor gene mutants produce a partial complex of the pyruvate dehydrogenase which lacks the carboxylase component. It is not yet known whether or not this situation represents a disproportional synthesis of the constituent enzymes of the pyruvate dehydrogenase complex, i.e., production of smaller amounts of the carboxylase than required for the formation of the enzyme complex.The results are discussed regarding their significance for the regulation of protein biosynthesis in E. coli in connection with similar data of other authors ( Jacob and Monod 1961; Beckwith 1963, 1964) obtained with the lactose system of the same organism.
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3.
Summary Before x-raying young pupae of Ephestia kühniella were treated for 6 hours with low (–7 o, +3°C) or high (+30 o, +35 o, +40°C) temperatures. The mutation rates of four types of scale mutations (somatic mutations) were influenced by these temperature treatments in a different manner. In consequence there were different mutation spectra at the applied temperatures. The relation of mutation ES 1 to mutation ES 2 was 5:1 in the –7°C group and 11:1 in the +35°C group. The differences are statistically significant.
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Die Untersuchung wurde vom Bundesministerium für Atomkernenergie und Wasserwwirtschaft unterstützt. 相似文献
4.
Summary By means of partial illumination with small spots of monochromatic light, polarized obliquely to the cell axis, we could demonstrate that the phytochrome molecules in Mougeotia are oriented in a spiral pattern around the cell surface. The lines of this spiral form an angle of about 45 o with the cell axis. The degree of exactness of this orientation has been discussed.
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Herrn Professor Dr. E. Heitz zum 70. Geburtstag. 相似文献
5.
Summary Dose response curves of 4 somatic mutations of Ephestia kühniella were established for the dose-range between 100 and 1000r of X-rays after six hours of pretreatment in different temperatures (+3 and +35°C). The curves are non-linear and can be fitted by the equation y=ax
b, were a is a constant, which is different for each mutant type, while b is the same for all four mutants. The values of a and b vary with the pre-irradiation-temperature. The exponent b is higher after a high temperature-treatment than after a low one. The difference b
35
o-b 3
o is the same for all mutants. The sensitivity of the mutation process (a) goes down after the warm treatment compared to the cold one. The direction of the change is the same for all mutants, but the difference between the treatments is proportionally higher in the less frequent types (ES 2 and ES 4) than in the more frequent mutants (ES 1 and ES 3). This leads to differences in the mutational spectrum, which — at certain doses — are as pronounced as to make the different mutant types show different reactions towards the same treatment (cold treatment, for example, yields more ES 2 and less ES 1 than a warm one at doses from about 500 r up to about 1300 r).The investigations may serve as an example for the fact, that a change in the mutational spectrum does not necessarily imply a different reaction of the mutant types to the modifying agent, but that it can be brought about as well by an analogous change in the parameters of their dose effect curves.
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Die Untersuchungen wurden unterstützt von der Deutschen Forschungsgemeinschaft und dem Bundesministerium für Atomkernenergie. 相似文献
6.
A spontaneous mutant of Methanothermobacter thermautotrophicus resistant toward the ATP-synthase inhibitor N, N′-dicyclohexylcarbodiimide (DCCD) was isolated. DCCD normally inhibits methanogenic electron-transport-driven ATP synthesis,
however, the DCCD-resistant strain exhibited methanogenesis in the presence of 300 μmol/L DCCD. Total ATP synthesis was shown
to be higher in the mutant strain, both in the presence and absence of DCCD. These results suggested a modification in the
ATP-synthesizing system of the mutant strain. Using Blue Native PAGE combined with MALDI TOF/TOF mass spectrometry, increased
concentrations of both the A 1 and A o subcomplexes of the A 1A o-type synthase were identified in the mutant strain. However, no alterations were found in the structural genes ( atp) for the A 1A o ATP synthase. The results imply that DCCD resistance is a consequence of increased A 1A o ATP synthase expression, and suggest that genes involved in regulating synthase expression are responsible for DCCD resistance. 相似文献
7.
Summary The serological study of 26 new strains of Bacillus thuringiensis (of which the biochemical features are also given) makes it possible to classify these strains into: 1 o Strains which are in concordance with the six serotypes previously described. 2 o Strains which have a new H antigen. Here, we describe two new serotypes: serotype 7 ( aizawai), serotype 8 ( morrisoni).
On the other hand, the serological study of five new strains of B. thuringiensis belonging to serotype 4 shows that the H 4 antigen must be divided into ?sub-factors?: ?4 a, 4b? to be found in the strains sotto, dendrolimus, T.84-A, L (Grig) and
?4 a, 4 c? to be found in the strains Pil 94, 1748 and Rhodesia.
Table 6 gives the present statute of the B. thuringiensis strains' classification by the flagellar agglutination technic.
Avec la collaboration technique de M. Lechevallier et T. Le Borgne.
Nous remercions vivement les collègues qui ont bien voulu nous adresser des cultures et nous nous tenons à la disposition
de tous ceux qui seraient intéresés par la détermination de l'antigène H de leurs souches.
Nous remercions également notre collègue Le Minor pour ses précieux conseils. 相似文献
8.
Résumé Les œufs de la pyrale du ma?s, Ostrinia nubilalis (Hübner), sont très sensibles à Metarhizium anisopliae (Metsch.)/Sorokin et Paecilomyces fumosoroseus (Wize) (Brown-Smith). Toutes conditions égales par ailleurs, les premiers stades larvaires meurent plus vite mais dans une
proportion plus faible que les stades plus agés. Beauveria bassiana (Bals.) (Vuillemin) n o 147 et M. anisopliae n o 139 sont particulièrement pathogènes pour ce stade tandis que P. fumoso-roseus attaque facilement les chrysalides. Par adjonction d'une dose faible de chlorpyriphos on sensibilise les larves à la mycose.
Les chenilles diapausantes sont très sensibles à la mycose puisque même des doses très faibles (40 sp/cm 2) tuent plus de 50% de la population.
Summary The egges of the European corn borer,Ostrinia nubilalis (Hübner) are very susceptible toMetarhizium anisopliae (Metsch.) Sorokin andPaecilomyces fumoso-roseus (Wize) (Brown-Smith). Whereas all the other conditions are equal, the 1 st larval instars die quicker but in a lower proportion
than the later.Beauveria bassiana (Bals.) Vuillemin no 147 andM. anisopliae no 139 are especially pathogenic to this instar whereasP. fumoso-roseus easily attacks the pupae. By adding a low dose of chlorpyriphos the larvae are more susceptible to mycosis.
The diapausing caterpillars are very susceptible to mycosis since doses even very low (40 sp/cm2 kill more than 50 % of the population.
Avec la collaboration technique de Mmes J. Goussard & L. Sénéchal. 相似文献
9.
Zusammenfassung Diese erste Arbeit über die Ichneumoniden von ?gypten behandelt 101 Arten, die verglichen und kommentiert werden. 9 dieser
Arten werden neu beschrieben. Sie schliessen sich an jene an, die in neueren Arbeiten von J. F. Aubert aus Nordafrika und dem Nahen Osten beschrieben worden sind. Ausserdem werden in der vorliegenden Arbeit 9 neue Synonymien
herausgestellt; für 2 Arten wird eines der Geschlechter zum ersten Male beschrieben. Diese Ichneumoniden, die lebhaft rot
und gelb gef?rbt sind, geh?ren zur Wüstenfauna, die im Nahen Osten und vor allem in der Sahara vorkommt. Schliesslich wird,
ebenfalls zum ersten Male, eine komplette Bibliographie aller Arbeiten über Ichneumoniden von Nordafrika und dem Nahen Orient
zusammengestellt.
Contribution à l'étude des Hyménoptères n o 7 (voir n o 6 in Ann. Sc. Nat., 12 e série, 8, 1966, p. 391–493). 相似文献
10.
Summary Prometaphasic chromosomes of Gorilla, Homo and Pan are compared, using R, Q, T and H-bands techniques in complement of a previous work (Lejeune et al., 1973). Various mechanisms of chromosomal rearrangements are demonstrated with particular reference to heterochromatic segments. Some phylogenic conclusions are proposed.
Zusammenfassung Prometaphase-Chromosomen von Gorilla, Mensch und Schimpanse werden mit hilfe der R-, Q-, T- und H-Bandentechnik verglichen; frühere Arbeiten (Lejeune et al., 1973) werden dadurch ergänzt. Verschiedene Mechanismen von Chromosomen-Rearrangements werden dargestellt; dabei finden die Heterochromatin-Segmente besondere Beachtung. Einige phylogenetische Folgerungen werden gezogen.
Travail de l'E.R.A. n o 47 du C.N.R.S. 相似文献
11.
After two selfing generations of two different Triticum turgidum – Aegilops ovata amphiploids carrying the Ph1 gene, or lacking it ( ph1c mutant), karyotypes of their offspring were scored by GISH (genomic in situ hybridization). On average, the chromosome number
was lower than expected (56 chromosomes) on the basis of the parental constitutions ( T. turgidum, AABB, 2n=4 x=28; Ae. ovata, M oM oU oU o, 2n=4 x=28). The lost chromosomes belonged to the wild Aegilops species. The two families differed greatly by their number of intergenomic translocations, also detected by GISH. The ph1c family showed nine translocations over 12 plants while only one translocation was observed in the Ph1 family. All exchanges involved either the M o and U o chromosomes or the M o and wheat chromosomes, the size of the exchanged segment ranging from 3% to 36% of the total chromosome length. The results
suggest an epistatic effect of the ph1c deletion over the genetic diploidizing system that operates in Ae. ovata since translocated chromosomes are most-likely derived from homoeologous recombination. The potential of these results for
wheat breeding programmes is also considered.
Received: 28 November 2000 / Accepted: 20 March 2001 相似文献
12.
Résumé L'étude de la sensibilité des chenilles de Spodoptera littoralis
Boisd. à des doses croissantes de spores de Nomuraea rileyi (F.) Samson, montre que le 6 e et dernier stade est plus résistant que le 1 er et surtout les 4 e et 5 e stades larvaires. La virulence du pathotype N. rileyi n o 5 à l'égard des larves de cette noctuelle est élevée puisque le temps léthal 50 % (TL 50) est de 6 j en moyenne. Pendant
l'incubation de la maladie les chenilles continuent de s'alimenter mais l'infection peut réduire jusqu'à 60 % la prise alimentaire
par rapport à la consommation des larves des lots témoins.
Toutes conditions égales par ailleurs, la mortalité provoquée par N. rileyi n o 5 après traitement des larves nouvelles-nées est supérieure lorsque les insectes sont maintenus à 25°C par rapport à celle
constatée à 20°C. Cependant pour une dose d'inoculum élevée, les conditions thermiques (20°, 25° ou 28°C), ne modifient pas
sensiblement la réponse à l'infection par N. rileyi n o 5 alors qu'elles limitent l'efficacité d'un pathotype moins virulent: Paecilomyces fumoso-roseus
Wize no o 39.
Summary Laboratory studies were conducted to determine the susceptibility of various larval instars of the cotton leafworm,Spodoptera littoralis
Boisd. to different spore doses ofNomuraea rileyi (F.)Samson to investigate the influence of temperature on the infection by this fungus and byPaecilomyces fumosoroseus
Wize. Contaminations were obtained by direct spraying on larvae in tower apparatus or by feeding of larvae on treated pieces of
leaf during 48 h or 72 h. The influence of cryptogamic infection on food consumption was studied by measuring surfaces of
standard cabbage leaf disces submitted to treated and control larvae.
Angular values mortality rates were submitted to the 2- or 3-way analysis of variance and comparisons of means were made by
theDuncan's test. In some cases we have also considered the time-mortality and the dose-mortality curves.
The 6th instar was more resistant than all other tested instars. TL50 were found to be 6 days in most cases. During incubation
of the disease, larvae continued to feed, but food consumption could be reduced at 40 % of controls.
Larval mortality due toN. rileyi No 5, recorded after 8 days of incubation, was higher at 25°C than at 20°C. Nevertheless, at high dosage, efficiency ofN. rileyi No 5 was not affected by temperature at 20°, 25° and 28°C. The other pathotype,P. fumoso-roseus No 39 was more effective at 20°C than at 25° and 28°. At 32°C, the temperature, unfavourable to fungal growth, limited mortality
at non significant rates.
Avec la collaboration technique de H. Vermeil de Conchard. 相似文献
13.
A model is proposed for the d-galactoside-H +( −OH) transporter of Escherichia coli that accounts for essentially all the experimental observations established for this system to date. In this model, the functional unit is postulated to be a dimer (consisting of two copies of lacY-specified polypeptide) which spans the membrane with a 2-fold symmetry axis in the membrane plane (Lancaster, J.R. (1978) J. Theor. Biol. 75, 35–50). The functional dimer is assumed to possess a single pore flanked by an inner gate (g i) and an outer gate (g o) and encompassing two oppositely oriented galactoside binding sites, designated m and μ. When g o is open and g i is closed under non-energized conditions, binding site m adopts a configuration defined as State A (i.e., m oA) exhibiting high affinity toward Class G a galactosides (thiodigalactoside, melibiose, α- p-nitrophenylgalactoside) but low affinity for Class G b galactosides (lactose, β- o-nitrophenylgalactoside, β-isopropylthiogalactoside), whereas binding site μ adopts State B (i.e., μoB) displaying relatively high affinity toward Class G b galactosides but comparatively low affinity for Class G a galactosides; further, each m oA : μoB dimer contains one thiol group whose reaction with N-ethylmaleimide inactivates the transporter unless blocked by galactoside binding at site m oA, while the second homologous thiol of the dimer is unreactive toward thiol reagents. Translocation of the m oA : μoB dimer involves closing of g o followed by opening of g i, and causes the two thiols (as well as sites m and μ) to interchange roles in a symmetrical fashion: m oA : μoB ↔ m iB : μiA. In the presence of a substantial (negative) transmembrane Δμ~ H+, the m : μ dimer is postulated to undergo an electrogenic protein conformational change to a second form, *(m : μ), in which both sites m and μ possess low affinity toward internal Class G b substrates; galactoside transport in both m : μ and *(m : μ) is assumed to be coupled to H +-symport ( −OH-antiport) with a stoichiometry of approximately 1 : 1. Finally, five characteristic predictions of the half-sites model are outlined for further tests of its validity. 相似文献
14.
The polymorphism of apolipoprotein E (Apo E) in man is controlled by two codominant alleles, Apo En and Apo Ed, at the Apo E-N/D locus and by two alleles, the dominant, Apo E4+, and the recessive, Apo E4o, at the Apo E4 locus. Frequency distribution analysis of Apo E phenotypes demonstrated a highly significant association between both systems (P ~ 1%). The Apo E4-(+) variant was about twice as frequent in phenotype Apo E-N (30.1%) than in phenotype Apo E-ND (16.4%). The phenotypic combination Apo E-D/-E4(+) was not observed. The segregation of Apo E phenotypes in informative matings is consistent with a close linkage of both loci. The results may be explained by different models. On the basis of the present data, these models cannot be distinguished by formal genetic criteria. (1) Haplotypes Apo En/E4+, Apo En/E4o, and Apo Ed/E4o determine the different phenotypes, and a linkage disequilibrium exists of Δ = .0147 between the E-N/D and E4 loci. (2) The fourth haplotype, Apo Ed/E4+, exists, but the gene E4+ is not expressed in coupling with Apo Ed. The four-haplotype model seems more attractive in view of Apo E-N/D polymorphism's quantitative character and of biochemical results, which show that phenotypes Apo E-N and Apo E-D differ in the apparent molecular weight (Mr) of the respective major Apo E polymorphic form. Hence, the Apo E-N/D locus may control structural genes involved in the posttranslational modification of Apo E. (3) Finally, there may exist only one Apo E structural gene locus but with mutations at two sites susceptible to posttranslational modification. 相似文献
15.
Summary Transfer of a non-Mendelian neamine-dependent ( nd) mutant to an antibioticfree medium results in neamine-sensitive and neamine-resistent revertants. These reversions are caused by extranuclear mutations.The neamine-sensitive revertants are no more able to split off nd-cells after back-donation to neamine containing medium. Therefore they are different from the streptomycin-sensitive revertants of a streptomycin-dependent ( sd) mutant. These mutants were capable of sd-segregation though their potence of sd-segregation diminished on antibiotic-free medium with increasing time of cultivation.The different behaviour can be explained by the fact that many sd-genes are present which have to be appointed to the mitochondria. On the other side, the nd-gene exists only in few copies and is located therefore in the chloroplast.Several experiments with differing methods are discussed to localize the extranuclear genes.
Vorgelegt durch G. Melchers 相似文献
16.
The functional mechanism of the F 1F o ATP synthase, like many membrane transporters and pumps, entails a conformational cycle that is coupled to the movement of H + or Na + ions across its transmembrane domain, down an electrochemical gradient. This coupling is an efficient means of energy transduction and regulation, provided that ion binding to the membrane domain, known as F o, is appropriately selective. In this study we set out to establish the structural and energetic basis for the ion-binding selectivity of the membrane-embedded F o rotors of two representative ATP synthases. First, we use a biochemical approach to demonstrate the inherent binding selectivity of these rotors, that is, independently from the rest of the enzyme. We then use atomically detailed computer simulations of wild-type and mutagenized rotors to calculate and rationalize their selectivity, on the basis of the structure, dynamics and coordination chemistry of the binding sites. We conclude that H + selectivity is most likely a robust property of all F o rotors, arising from the prominent presence of a conserved carboxylic acid and its intrinsic chemical propensity for protonation, as well as from the structural plasticity of the binding sites. In H +-coupled rotors, the incorporation of hydrophobic side chains to the binding sites enhances this inherent H + selectivity. Size restriction may also favor H + over Na +, but increasing size alone does not confer Na + selectivity. Rather, the degree to which F o rotors may exhibit Na + coupling relies on the presence of a sufficient number of suitable coordinating side chains and/or structural water molecules. These ligands accomplish a shift in the relative binding energetics, which under some physiological conditions may be sufficient to provide Na + dependence. 相似文献
17.
A soil isolate, Pseudomonas putida strain A10L that utilizes mandelate via the mandelate pathway was mutagenized by transposon Tn5-Mob insertion and a mutant 168 lacking mandelate racemase (MR) and a mutant 254 lacking benzoylformate decarboxylase (BFDC) were obtained. Expression of ( S)-mandelate dehydrogenase (MDH), BFDC, NAD + -dependent benzaldehyde dehydrogenase (BDH) and NADP + -dependent BDH in the MR-lacking mutant was not affected by the insertion, and it was inducible similarly to the wild type strain. On the other hand, expression of MR and MDH in the BFDC-lacking mutant was low and constitutive, and NAD + - and NADP + -dependent BDHs were produced at a rather high level under non-induced conditions by the mutant. Genes for MR ( mdlA), MDH ( mdlB), and BFDC ( mdlC) were indicated to be organized in an operon in the order of mdlCBA. Optical resolution to obtain ( R)-mandelate, a useful synthon for pharmaceuticals, was shown to be performed with the MR-lacking mutant. 相似文献
19.
Abstract Adenylosuccinate synthetase from Saccharomyces cerevisiae was investigated in order to find a structural explanation for its ability to bind specifically to single-stranded ARS elements (autonomously replicating sequences). Using the E. coli enzyme as template, a model for the structure of adenylosuccinate synthetase from S. cerevisiae was generated and subsequently refined by molecular dynamics techniques. The resulting three-dimensional structure offers an explanation for the DNA binding activity of the yeast enzyme by revealing a distinct basic region that is not present in the homologous enzymes from other organisms. The model is also in good agreement with biochemical data available for a mutant protein in which Glycine 252 is replaced by Aspartate. On the basis of the model a significant structural distortion near the catalytic center was predicted for this mutant, corresponding well to the enzymatic inactivity observed. The mutant enzyme shows larger structural fluctuations than the wild-type protein according to the results of two independent molecular dynamics simulations. 相似文献
20.
To study the post-uroporphyrin steps in heme and chlorophyll biosynthesis in Chlorobium, we attempted to clone the uroporphyrinogen decarboxylase ( hemE) gene. A Chlorobium genomic library was used to transform a restriction-minus Salmonella typhimurium strain. The recombinant DNA molecules were transduced into an auxotrophic Salmonella double mutant ( hemA −
hemE −) by phage P22. Faster-growing colonies indicated complementation of the hemE mutation. Each clone was tested by backcross transduction of the mutant. Growth rates of the confirmed clones in LB medium
were comparable to wild-type Salmonella. HPLC analysis of the substrate (uroporphyrinogen) and the product (coproporphyrinogen) of the decarboxylase activity was
performed in one such clone. This clone showed an active hemE gene within a 4-kb insert.
Received: 21 February 2002 / Accepted: 8 May 2002 相似文献
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