-
Volume 76,
Issue 2,
1973
Volume 76, Issue 2, 1973
- Biochemistry
-
-
-
Inhibition by 3-Deoxy-3-Fluoro-D-Glucose of the Utilization of Lactose and Other Carbon Sources by Escherichia coli
More LessSummary: 3-Deoxy-3-fluoro-D-glucose (3FG) was converted to 3FG-6-phosphate by the phosphoenolpyruvate-dependent phosphotransferase system in frozen and thawed Escherichia coli. Up to 0.03g 3FG was taken up/g bacterial dry wt. Uptake of 3FG was not lethal, though 3FG at 0.1 to 10 mM completely prevented or severely inhibited utilization of lactose, fructose, glycerol, succinate, acetate and pyruvate. It prevented lactose utilization by inhibition of the synthesis and activity of both β-galactosidase and galactoside permease. 3FG-resistant mutants were isolated which were deficient in the Enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system specific for glucose and for 3FG. Our findings support the view that the ‘glucose effect’ may depend upon glucose itself or a glucose derivative, rather than upon catabolic products.
-
-
-
-
Sulphur Metabolism of Puccinia graminis f.sp. tritici in Axenic Culture
More LessSummary: Axenic cultures of Puccinia graminis f. sp. tritici cannot reduce sulphate for sulphur-amino-acid synthesis. Although [35S]sulphide is incorporated into these amino acids, the fungus still has a nutritional requirement for a sulphur amino acid. Most of the incorporated sulphide was found in the culture filtrate in the form of cysteine, s-methylcysteine, glutathione and cysteinylglycine. There were appreciable amounts of labelled methionine in mycelial protein but very little of this amino acid appeared in the culture filtrate. The results indicate that the nutritional requirements for sulphur amino acids by the rust fungus is caused by loss of cysteine and some of its derivatives into the medium.
-
-
-
The Metabolism of Lactate and Pyruvate by Pseudomonas AM1
More LessSummary: Pseudomonas AMI, which can grow on C1 compounds, also grows well on pyruvate and lactate. Extracts of the pyruvate-grown organism catalysed the synthesis of only small amounts of phosphoeno/pyruvate directly from pyruvate. Experiments tracing the incorporation of radioactivity into bacterial constituents from pyruvate or lactate, each labelled in the C-1 or C-3 position, indicated that these substrates are mainly assimilated after removal of the C-1 atom. A mutant, C5, of Pseudomonas AMI was isolated by a procedure intended to select organisms lacking phosphoeflo/pyruvate carboxylase. Although this enzyme was present in mutant C5, growth on lactate or pyruvate was impaired and there was no growth on C1 compounds or ethanol. Good growth on each of these substrates was restored by a supplement of glyoxylate or glycollate.
A scheme is proposed for the assimilation via malate synthase and phosphoenol-pyruvate carboxykinase of the C2 fragment produced from pyruvate and lactate.
-
-
-
An Electron Microscopic Study of Anaerovibrio lipolytica (Strain 5s) and Its Lipolytic Enzyme
More LessSummary: The extracellular lipolytic activity produced by Anaerovibrio lipolytica strain 5s is associated with large particles composed of protein, lipid and nucleic acid. These particles have a membranous appearance when viewed by electron microscope and in the ultracentrifuge they have a sedimentation coefficient (S 20, W) of 13.1 S. Numerous ‘blebs’ are associated with the walls of Anaerovibrio lipolytica during the phase of logarithmic growth when lipase production is maximal. The lipolytic enzyme is released from the bacteria without visible bacterial lysis.
-
- Development And Structure
-
-
-
Release of Protoplasts from Schizophyllum commune by Combined Action of Purified α-1,3-Glucanase and Chitinase Derived from Trichoderma viride
More LessSummary: Protoplast release from young mycelium of Schizophyllum commune by a lytic enzyme preparation from Trichoderma viride was accompanied by degradation of the three wall polymers, s-glucan, r-glucan and chitin. Part of the s-glucan was resistant. The resistance of s-glucan to enzymatic degradation increased with culture age and concomitantly the yield of protoplasts was reduced. Isolated s-glucan was also partly resistant to degradation, probably due to its crystallinity. In living cells s-glucan protected chitin and possibly r-glucan against degradation by external enzymes. s-glucanase, r-glucanase, chitinase and exo-laminarinase were purified from the Trichoderma enzyme mixture. Addition of only s-glucanase and chitinase was essential for protoplast release; r-glucan was degraded endogenously.
-
-
-
-
Effects of the Self-Inhibitor of Dictyostelium discoideum on Spore Metabolism
More LessSummary: The effects of the self-inhibitor, N,N-dimethylguanosine, on the metabolism of spores of Dictyostelium discoideum were investigated. It is concluded that since both self-inhibited and activated spores had similar initial Q O2 values, the site of action of the self-inhibitor was not on respiratory metabolism. Incorporation of [U14C]glucose revealed that organic acids and amino acids accumulated in self-inhibited spores and that protein synthesis was inhibited. Succinic acid accumulated only when the activated self-inhibited spores became anaerobic so its accumulation was not directly related to self-inhibition. Phenylalanine, methionine and tryptophan were absent in dormant spores but appeared after heat-activation and accumulated in self-inhibited spores. The accumulation of amino acids was related to the inability of self-inhibited spores to synthesize protein. In vivo analysis showed that protein synthesis began early in spore germination and that the self-inhibitor immediately arrested this process when added to activated spores and slowed it when added to germinating spores. No effect of self-inhibitor on RNA synthesis during germination was detected. Thus, we conclude that the self-inhibitor, a methylated base of guanine, regulated spore germination by preventing the synthesis of protein necessary for subsequent development.
-
-
-
Morphological Phases in the Swarm of Bacillus licheniformis
More LessSummary: The advancing edge of the active swarm of Bacillus licheniformis is surrounded with a fringe of non-flagellate, septate filaments. The mucoid portion of the colony is composed of short, flagellate bacilli. The two phases resemble Rough and Smooth forms occurring in the same colony.
-
- Genetics And Molecular Biology
-
-
-
Cytoplasmic Inheritance of the Timing of ‘Senescence’ in Podospora anserina
More LessSummary: Reciprocal crosses and repeated backcrosses have shown that the distance of growth before the first mycelium of a population exhibits ‘senescence’ and the rate at which the remaining mycelia exhibit ‘senescence’ are cytoplasmically inherited in several races of Podospora anserina. A nuclear gene (the plus mating type allele of race S) was found to influence the timing of ‘senescence’ in interracial hybrids carrying the cytoplasmic determinants of race A. Known nuclear genes segregated normally in the interracial crosses employed in the work.
-
-
-
-
Transduction of R Factors in Proteus mirabilis and P. rettgeri
More LessSummary: Phage 34 transduces some R factors to Proteus mirabilis strain 13. These trans-ductants can transmit the R factor by conjugation. Transduction frequencies vary from 1×10−5/plaque-forming unit (p.f.u.) adsorbed (higher than chromosomal marker transduction) to 5×10−8/p.f.u. adsorbed. Transduced drug resistance markers of other R factors were detected only in the presence of resident fi − factors in recipients and recombination between the R factors concerned could account for the fact that these transductants were able to transmit hybrid R factors by conjugation. Transduction of portions of R factors, including an fi + factor occurred and some transductants were unable to transmit transduced markers by cell-to-cell contact despite the presence of resident fi − R factors. In transductants which were conjugally infectious the transduced R factor did not appear to be associated with the genome of the phage. Incompatibility had no demonstrable effect on transduction rates. The presence of an fi − resident factor reduced transduction rates when these were measurable in the absence of the resident. In two cases which involved N group resident plasmids this reduction was possibly due to restriction and host modification of transduced R factor DNA. Because of the natural resistance of the P. rettgeri host only R factors which bore the marker for kanamycin resistance could be selected in transductions with phage 7.R49. Only a T group factor was transduced. The transduction frequency was similar to that of a chromosomal marker but transductants were non-infectious.
-
-
-
Independent Expression of the A Gene of the Tryptophan Operon of Escherichia coli during Tryptophan Starvation
More LessSummary: Two complementary frameshift mutations in the trpA gene of Escherichia coli have been isolated following recombination of the pseudowild double mutant with the wild-type strain. One of these mutations recombines with a third, distal frameshift mutation to give a slow-growing Trp+ strain. Consideration of the relevant RNA codon sequences suggests that the slow-growing recombinant should contain a unique tryptophan codon in the altered reading phase between the frameshift mutations. This prediction has been verified by analysis of the purified tryptophan synthetase A protein from the double mutant. The preferential synthesis of A protein normally associated with prolonged tryptophan starvation is eliminated in the strain which has a tryptophan residue in its A protein.
-
-
-
Ultraviolet Sensitivity, Spontaneous Mutability and DNA Degradation in Escherichia coli Strains Carrying Mutations in uvr and rec Genes
More LessSummary: Escherichia coli uvr502 bacteria have a higher spontaneous mutability and are 4.6 times more u.v.-sensitive than isogenic wild-type bacteria. Bacteria deficient in dimer excision (uvrA6) are 15 times more u.v.-sensitive than isogenic uvrA + bacteria. Double mutant uvrA6 uvr502 bacteria are only 1.5 times more u.v.-sensitive than uvrA6 bacteria and double mutant uvr502recA56 bacteria were as u.v.-sensitive as recA56 bacteria, suggesting that there exists a uvrA +- and recA +- dependent repair pathway which is blocked by the uvr502 mutation. We suggest that the uvr502 mutation affects primarily the excision repair pathway. Strict additivity of the uvr502 and recB21 mutations on u.v. sensitivity suggests that recB +-mediated repair acts in part of repair pathway different from excision repair. U.v.-induced DNA degradation in the uvr502 bacteria is only slightly greater than that in uvr + bacteria and the uvr502 mutation does not affect the ဘrecklessမ character of u.v.-induced DNA breakdown in the recA56 bacteria. The avr502-uvrA6 and uvr 502 rec A56 or uvr502recB21 double mutants have spontaneous mutation frequencies similar to that of the single uvr502 strain.
-
-
-
The Sensitivity of Suppressed and Unsuppressed lon Strains of Escherichia coli to Chemical Agents which Induce Filamentation
More LessSummary: The sensitivities of lon strains of Escherichia coli to the filament inducing agents nalidixic acid, gentian violet, crystal violet and penicillin were examined. The strains used included those in which the lon gene is suppressed by sul, exr and rec as well as strains in which the Lon phenotype is expressed. The sensitivity of the bacteria to agents which act on DNA was reduced when lon was suppressed, but the extent of the decrease in sensitivity was dependent on the mechanism by which suppression was effected. Sensitivity to penicillin, on the other hand, was reduced only in the sul strain and by a mechanism which appears to be independent of the direct suppression of lon. A model to account for these results indicates possible sites at which the lon, sul, exrA and recA genes are expressed.
-
- Medical Microbiology
-
-
-
Subunit Structure of Cholera Toxin
More LessSummary: Two types of subunit, with molecular weights estimated to be 28000 and 8000, were demonstrated in the cholera exo-enterotoxin by sodium dodecylsulphate polyacrylamide electrophoresis. The light (L) component but not the heavy (H) was demonstrable in the antigenically identical natural toxoid. A spilt of the H component by reduction and alkylation suggested it to be a disulphide-bridged dimer.
Gel filtration at acid pH permitted separation of the H and L subunits in isolated form. Fractions with isolated subunits were non-toxic (skin test), in contrast to fractions with intermediate filtration rate containing both subunits. Fractions with a L:H ratio of about 3.5 were even more toxic than the intact toxin (L:H ratio about 2). Addition of the isolated subunits to toxic fractions generally caused inhibition and only exceptionally potentiation of toxicity.
The data suggest that the cholera toxin might consist of an aggregate of seven L and one H subunits while the natural toxoid seems composed of only the aggregated L chains.
-
-
- Physiology And Growth
-
-
-
Sulphonamide-induced ‘Thymineless Death’ in Escherichia coli
R. Then and P. AngehrnSummary: The conditions for induction of thymine deficiency by sulphonamides and their effect on viability were investigated in Escherichia coli. In minimal medium, sulphonamides led to a slight decrease in the viable count over a prolonged length of time. This decrease was more pronounced in Casamino acid supplemented medium. Concentrations of as low as 1 μg/ml of sulphamethoxazole or some other sulphonamides killed up to 99.9% of bacteria within 4 h after manifestation of inhibition in media supplemented by Casamino acids and inosine. No strict relation was found between sulphonamide concentration and the number of surviving bacteria. In all experiments sulphonamides exerted their effects after a time lag of 3 to 4 h. Addition of thymidine prevented death. Effects similar to those in media containing Casamino acids and inosine were demonstrated in growth medium containing human blood. The possible role of this kind of action of sulphonamides in chemotherapy is discussed.
-
-
-
-
Lytic Plaque Formation and Variation in Virus Titre among Strains of Penicillium chrysogenum
More LessSummary: Strains of Penicillium chrysogenum derived from a virus-infected culture have been investigated for reduction in virus titre. These strains were obtained following treatment with either heat (74°C) or specific antimetabolites. Virus titres were measured with a combination of immunological and radiochemical assays. One strain was cured of the mycophage and exhibited an increased growth rate and stability. Other strains, which show an apparent reduction in intracellular virus titre, actually released increased levels of virus from cells. Lytic plaques developed when infected strains were grown on an unbuffered, high lactose-containing medium, and virus titres could be correlated with plaque formation. All strains, regardless of virus titre, retained the ability to synthesize penicillin.
-
-
-
Growth of Aspergillus nidulans in a Thin Liquid Layer
More LessSummary: Growth of Aspergillus nidulans in a thin layer of liquid minimal medium was exponential. The dry-weight doubling time at 37°C was 10 h when the inoculum density was 1.3×105 viable spores/ml. Compared with shake-flask cultures, growth was equally fast, but exponential growth ceased sooner. Aerial conidiation occurred, however, and the method was simple and permitted the collection of extracellular products in the absence of cell breakage.
-
-
-
The Development of ‘Senescence’ in Podospora anserina
More LessSummary: The growth of a mycelium of Podospora anserina ceases after a period of time characteristic for a given race. As the mycelium grows out from the germinated spore it passes through two physiological states; a ‘non-senescent’ state where the growth potential of the various regions of the growing mycelium remains constant and a ‘senescent’ state where the growth rate remains constant but the growth potential of the mycelium progressively decreases.
The ‘senescent’ state is apparently due to the presence of a variant cytoplasmic determinant which is discontinuously distributed among the cells of the mycelium and whose concentration increases exponentially during growth. The rate of transformation from the ‘non-senescent’ to ‘senescent’ state is directly proportional to the number of hyphae per mycelium. The median length of growth can be greatly extended by short periods of growth in the presence of cycloheximide or cyanide, but not by a variety of other drugs which inhibit mitochondrial functions.
-
- Short Communications
-
Volumes and issues
-
Volume 171 (2025)
-
Volume 170 (2024)
-
Volume 169 (2023)
-
Volume 168 (2022)
-
Volume 167 (2021)
-
Volume 166 (2020)
-
Volume 165 (2019)
-
Volume 164 (2018)
-
Volume 163 (2017)
-
Volume 162 (2016)
-
Volume 161 (2015)
-
Volume 160 (2014)
-
Volume 159 (2013)
-
Volume 158 (2012)
-
Volume 157 (2011)
-
Volume 156 (2010)
-
Volume 155 (2009)
-
Volume 154 (2008)
-
Volume 153 (2007)
-
Volume 152 (2006)
-
Volume 151 (2005)
-
Volume 150 (2004)
-
Volume 149 (2003)
-
Volume 148 (2002)
-
Volume 147 (2001)
-
Volume 146 (2000)
-
Volume 145 (1999)
-
Volume 144 (1998)
-
Volume 143 (1997)
-
Volume 142 (1996)
-
Volume 141 (1995)
-
Volume 140 (1994)
-
Volume 139 (1993)
-
Volume 138 (1992)
-
Volume 137 (1991)
-
Volume 136 (1990)
-
Volume 135 (1989)
-
Volume 134 (1988)
-
Volume 133 (1987)
-
Volume 132 (1986)
-
Volume 131 (1985)
-
Volume 130 (1984)
-
Volume 129 (1983)
-
Volume 128 (1982)
-
Volume 127 (1981)
-
Volume 126 (1981)
-
Volume 125 (1981)
-
Volume 124 (1981)
-
Volume 123 (1981)
-
Volume 122 (1981)
-
Volume 121 (1980)
-
Volume 120 (1980)
-
Volume 119 (1980)
-
Volume 118 (1980)
-
Volume 117 (1980)
-
Volume 116 (1980)
-
Volume 115 (1979)
-
Volume 114 (1979)
-
Volume 113 (1979)
-
Volume 112 (1979)
-
Volume 111 (1979)
-
Volume 110 (1979)
-
Volume 109 (1978)
-
Volume 108 (1978)
-
Volume 107 (1978)
-
Volume 106 (1978)
-
Volume 105 (1978)
-
Volume 104 (1978)
-
Volume 103 (1977)
-
Volume 102 (1977)
-
Volume 101 (1977)
-
Volume 100 (1977)
-
Volume 99 (1977)
-
Volume 98 (1977)
-
Volume 97 (1976)
-
Volume 96 (1976)
-
Volume 95 (1976)
-
Volume 94 (1976)
-
Volume 93 (1976)
-
Volume 92 (1976)
-
Volume 91 (1975)
-
Volume 90 (1975)
-
Volume 89 (1975)
-
Volume 88 (1975)
-
Volume 87 (1975)
-
Volume 86 (1975)
-
Volume 85 (1974)
-
Volume 84 (1974)
-
Volume 83 (1974)
-
Volume 82 (1974)
-
Volume 81 (1974)
-
Volume 80 (1974)
-
Volume 79 (1973)
-
Volume 78 (1973)
-
Volume 77 (1973)
-
Volume 76 (1973)
-
Volume 75 (1973)
-
Volume 74 (1973)
-
Volume 73 (1972)
-
Volume 72 (1972)
-
Volume 71 (1972)
-
Volume 70 (1972)
-
Volume 69 (1971)
-
Volume 68 (1971)
-
Volume 67 (1971)
-
Volume 66 (1971)
-
Volume 65 (1971)
-
Volume 64 (1970)
-
Volume 63 (1970)
-
Volume 62 (1970)
-
Volume 61 (1970)
-
Volume 60 (1970)
-
Volume 59 (1969)
-
Volume 58 (1969)
-
Volume 57 (1969)
-
Volume 56 (1969)
-
Volume 55 (1969)
-
Volume 54 (1968)
-
Volume 53 (1968)
-
Volume 52 (1968)
-
Volume 51 (1968)
-
Volume 50 (1968)
-
Volume 49 (1967)
-
Volume 48 (1967)
-
Volume 47 (1967)
-
Volume 46 (1967)
-
Volume 45 (1966)
-
Volume 44 (1966)
-
Volume 43 (1966)
-
Volume 42 (1966)
-
Volume 41 (1965)
-
Volume 40 (1965)
-
Volume 39 (1965)
-
Volume 38 (1965)
-
Volume 37 (1964)
-
Volume 36 (1964)
-
Volume 35 (1964)
-
Volume 34 (1964)
-
Volume 33 (1963)
-
Volume 32 (1963)
-
Volume 31 (1963)
-
Volume 30 (1963)
-
Volume 29 (1962)
-
Volume 28 (1962)
-
Volume 27 (1962)
-
Volume 26 (1961)
-
Volume 25 (1961)
-
Volume 24 (1961)
-
Volume 23 (1960)
-
Volume 22 (1960)
-
Volume 21 (1959)
-
Volume 20 (1959)
-
Volume 19 (1958)
-
Volume 18 (1958)
-
Volume 17 (1957)
-
Volume 16 (1957)
-
Volume 15 (1956)
-
Volume 14 (1956)
-
Volume 13 (1955)
-
Volume 12 (1955)
-
Volume 11 (1954)
-
Volume 10 (1954)
-
Volume 9 (1953)
-
Volume 8 (1953)
-
Volume 7 (1952)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)
Most Read This Month
