-
Volume 71,
Issue 1,
1972
Volume 71, Issue 1, 1972
- Biochemistry
-
-
-
An Obligately Autotrophic Mutant of Chlamydomonas dysosmos i a Biochemical Elucidation
More LessSUMMARY: Chlamydomonas dysosmos is a unicellular, flagellate, green alga. Wild-type cells, normally photosynthetic, are also facultatively heterotrophic, being capable of growth in darkness with acetate as sole source of carbon. A mutant induced by ultraviolet light lacked the ability to grow heterotrophically and formed negligible amounts of isocitrate lyase after 70 h in darkness with acetate, the specific activity being less than 3 % of that found in the wild-type. Uptake of acetate after 9 h was only 0.3 % of that by the wild-type. ATP increased slightly during the first 10 h after addition of acetate and thereafter decreased, in contrast to wild-type cells, in which ATP synthesis continued under similar conditions. Thus C. dysosmos could normally incorporate acetate for heterotrophic growth via the glyoxylate cycle but, in the mutant, this cycle was impaired, the alga being unable to synthesize isocitrate lyase and being thereby rendered obligately autotrophic.
-
-
-
-
Intermediary Metabolite Levels in Escherichia coli
More LessSUMMARY: The intra- and extracellular concentrations of a number of phosphorylated intermediary metabolites in Escherichia coli were measured radiochemically during growth in low phosphate (0.75 mM) media containing [32P]Pi. Distribution studies showed that most of the monophosphate metabolites were present in the supernatant medium outside the bacteria. This was much less marked for the di- and triphosphates, and was not due to bacterium lysis. Adenosine 3′,5′-cyclic monophosphate was present solely in the medium under all conditions tested. 3′,5′-Cyclic-AMP added to the medium was only partly effective in reversing repression of β-galactosidase synthesis by gluconate. This was not due to degradation of the nucleotide.
In another series of strains, chemical determinations were made of the intra-and extracellular concentrations of fructose 1,6-diphosphate and triose phosphate under varying conditions of growth in high phosphate (0·1 M) media; while most of the fructose 1,6-diphosphate remained inside the bacteria, triose phosphate was present largely in the medium. In all of these studies there was no correlation between the severity of catabolite repression and the concentrations of metabolites either inside the bacteria, or in the medium.
-
- Development And Structure
-
-
-
Sporulation in Bacillus subtilis. Characterization of Oligosporogenous Mutants and Comparison of Their Phenotypes with Those of Asporogenous Mutants
More LessSUMMARY: An investigation was undertaken to determine to what extent the properties of oligosporogenous (Osp) mutants allow them to be considered as a separate class of sporulation mutant, distinct from asporogenous (Sp-) mutants. Of thirty Osp mutants examined, seventeen at least had a phenotype which had previously been identified with a Sp- mutant. The majority of cells in an Osp culture either reached a particular stage in the sporulation process and then stopped, or in some cases went on to produce aberrant forms. Some of these aberrant forms have their counterparts in Sp- mutants described by other authors, but some present new features. The morphological and biochemical sequences were linked so that if the majority of cells were blocked at a certain stage, then the biochemical sequence stopped accordingly. The general similarity in behaviour between the two types of mutant is consistent with the assumption that at least some of the Osp mutants have leaky mutations in genes where mutation can also give rise to Sp- phenotypes. Evidence is presented to suggest that the ability of a cell of an Osp mutant to overcome its block, and so go on to form a spore, is a chance event when that stage in the process is reached. A mutant has been obtained in which the spores are octanol-resistant yet contain no measurable dipicolinate. In several other mutants the spores contained well-developed coat layers, but the cortex was poorly formed or completely missing.
-
-
-
-
An Ultrastructural Study of Precleavage Mitosis in the Myxomycete Arcyria cinerea
More LessSUMMARY: The precleavage mitotic division in Arcyria cinerea was intranuclear and involved no centrioles. The division was nearly synchronous throughout the sporangium although nuclei in the upper portion of the sporangium usually began to divide first. At metaphase nuclei were roughly spherical. Intranuclear spindle fibres were visible and appeared to terminate near the inner surface of the nuclear envelope. By telophase the nuclei were very elongated In late telophase the nuclear envelope broke first in the interzonal region and then at the poles. The reconstitution of the nuclear envelope appeared to involve remnants of the original envelope as well as small vesicular elements resembling short segments of rough endoplasmic reticulum. The chromosomal spindle fibres, as well as some interzonal fibres, usually persisted until the nuclear envelope was completely reconstituted around a daughter nucleus. The division was completed by the time spore cleavage began in the sporangium.
-
-
-
Ultrastructural Studies on the Genus Actinomyces
More LessSUMMARY: The fine structure of Actinomyces bovis, A. israelii, A. naeslundii, A. odontolyticus and A. viscosus was investigated by electron microscopy of chemically fixed and freeze-etched preparations. All species were grown in Brain Heart Infusion broth and examined after 4 and 7 days of growth. The fine structure of all species was similar. The thickness of the wall differed consistently, with A. israelii having the thickest. The mode of growth and division was of a uniform pattern. During growth lateral protrusions were formed, followed by two successive cell divisions which were perpendicular to each other and resulted in the formation of cell clusters. Usually these clusters consisted of two rows of cells at approximately right angles.
-
-
-
Bacterial Endosymbiosis in Paramecium aurelia: Bacteriophage-like Inclusions in a Kappa Symbiont
More LessSUMMARY: The bacterial endosymbiont kappa of stock A35 of Paramecium aurelia (syngen 2) carries virus-like inclusions after it has developed a refractile or R body which is necessary for kappa to exert the killing effect.
In exponentially growing Paramecium, the proportion of symbionts bearing R bodies and virus-like inclusions is very low. On starvation, R bodies and virus-like inclusions reappear, and the proportion builds up to between one-quarter and one-half of the total number of symbionts in a cell. Thus the development of R bodies, virus-like inclusions and killing action is influenced by the environment of the host Paramecium cell.
-
-
-
Ultrastructure and Invertase Secretion of the Slime Mutant of Neurospora crassa
More LessSUMMARY: Electron micrographs of thin sections of cells of the slime mutantof Neurospora crassa showed that it, like artificially prepared protoplasts, possessed no cell wall. Invertase was produced by the mutant and appeared to be serologically identical to wild-type N. crassa invertase. The mutant secreted over 95 % of theinvertase into the medium whereas cells of the wild-type retained almost all the invertase. Theslime mutant hence resembles wild-type protoplasts in both structure and invertase secretion.
-
- Ecology
-
-
-
Nitrogenase Activity and Oxygen Sensitivity of the Paspalum notatum-Azotobacter paspali Association
More LessSUMMARY: Nitrogenase activity in the rhizosphere of a grass, Paspalum notatum, and its associated soil was measured by the reduction of acetylene. Roots of the cultivar ‘batatais’ colonized by Azotobacter paspali, when taken from the soil, produced 1 to 32 nmol C2H4/g dry wt/h, whereas the cultivar ‘pensacola’, which is not colonized by A. paspali, produced less than 0.5 nmol/g/h. There was a lag of 12 to 24 h before maximum, linear, rates of acetylene reduction were reached. Activity was almost completely inhibited in air or in the absence of O2 and was greatest at around pO2 0.04 atm. Activity of soil cores containing plants with leaves attached was little affected by pO2 and showed no lag. Soil-plant cores maintained in a 16 h day+8 h night showed no diurnal fluctuation in activity; as the dark period was extended, activity decreased but was restored on returning plants to the light. Roots and rhizomes had most activity, the soil very little and aerial parts none. Washing the roots removed less than half the activity. Disturbance of soil-plant cores decreased activity. The soil next to the root surface contained most A. paspali; more were associated with active plants than with less active plants. Sections of roots showed abundant bacteria adjacent to the root surface. Nitrogen fixation by the association was estimated to be up to 90 kg N/ha/annum.
-
-
-
-
The Metabolism of Starch, Glucose, Amino Acids, Purines, Pyrimidines and Bacteria by the Rumen Ciliate Entodinium simplex
More LessSUMMARY: Washed suspensions of Entodinium simplex grown in vitro and incubated anaerobically engulfed all the types of bacteria tested. At high bacterial densities Klebsiella aerogenes and Proteus mirabilis, two bacteria normally present in the growth medium, were taken up most rapidly. Entodinium simplex utilized bacterial amino acids for the synthesis of protein and no evidence was obtained for appreciable synthesis of protein from carbohydrate. No intercpnversion of amino acids occurred. Free and bacterial adenine, guanine and uracil were incorporated into protozoal nucleic acid: uracil was partially converted into cytosine. Free amino acids and glucose were taken up by the protozoa by two mechanisms, one predominant at high concentrations and the other at low concentrations. Glucose was incorporated, in intact protozoa, into both polysaccharide and bacteria and glucose had to be taken up by the protozoa before it was incorporated into the bacteria.
-
- Genetics And Molecular Biology
-
-
-
Sporulation in Bacillus subtilis. Genetic Analysis of Oligosporogenous Mutants
More LessSUMMARYMutations in 30 Oligosporogenous (Osp) mutants of Bacillus subtilis have been mapped by transduction with phage PBS-1. The sporulation phenotype of these mutants had previously been characterized biochemically and morphologically. The mutationsare situated in areas of the genome previously shown to be occupied by asporogenous (Sp-) mutations. Data from reciprocal transformation between Ospand Sp- mutations of indistinguishable phenotype suggest that one of the Osp mutations and at least one of the Sp- mutations may be located within the same gene.
-
-
- Medical Microbiology
-
-
-
Inhibition of the Interaction Between Fimbrial Haemagglutinins and Erythrocytes by D-Mannose and Other Carbohydrates
More LessSUMMARY: Many monosaccharides, oligosaccharides and their derivatives were tested as inhibitors of agglutination of guinea-pig or horse erythrocytes by Salmonella typhimuriumor Shigella flexneri bacteria bearing type-1 fimbriae. D-Mannose and certain derivatives of mannose were strongly inhibitory, and D-fructose moderately inhibitory. Modification of any of the hydroxyl groups at the C-2, C-3, C-4 or C-6 positions in the D-mannopyranosyl molecule caused failure to inhibit, showing that these groups were necessary for binding to the activesites of the fimbrial haemagglutinin. The α-configuration at the C-1 position in D-mannose was important and carbohydrates containing α-linked D-mannose were much more active inhibitors than those containing β-linked D-mannose, which were poor inhibitors or non-inhibitors. Yeast mannan also inhibited the fimbrial reaction. Attention is drawn to the remarkable degree of similarity ofthe inhibition pattern of the type-1 fimbrial haemagglutinin of bacteria with that of concanavalin-A, the jack bean haemagglutinin.
-
-
- Physiology And Growth
-
-
-
Are Plastids Derived from Prokaryotic Micro-organisms? Action of Antibiotics on Chloroplasts of Euglena gracilis
More LessSUMMARYOf 144 antibiotics examined with respect to their action on Euglena chloroplasts, 46 caused irreversible loss of plastids and most inhibited chlorophyll synthesis. These substances included structurally related compounds as well as degradation products of antibiotics. Antibiotics exhibiting bleaching activity were of two general types judged by their mechanisms of action in other systems:
1. Inhibitors of DNA synthesis ‘ anthramycin, edeine, porfiromycin, some mitomycins, myxin, nalidixic acid and its derivatives, novobiocin, primycin, rubiflavin, sarkomycin and streptonigrin;
2. Inhibitors of protein synthesis ‘ 29 antibiotics which carry a common molecular denominator in their structure (an aminohexose) and three antibiotics which lack aminosugar moieties: viomycin, streptogramin and pactamycin.
Only these two types of antibiotics permanently eliminated chloroplasts; antibiotics classified as possessing other mechanisms of action were not effective.
All these bleaching antibiotics inhibited replication of plastids in concentrations having no effect on normal Euglena division. A diluting-out of pathological plastids is the explanation of this ‘bleaching phenomenon’.
-
-
-
-
Effect of Evaporation Losses on Experimental Continuous Culture Results
More LessSUMMARY: Evaporation can lead to errors in the measurement of parameters such as yield and maintenance coefficient, using continuous cultures at dilution rates below 0·05 h-1.
-
-
-
Stimulation of Mitosis Following Fusion of Plasmodia in the Myxomycete Physarum polycephalum
More LessSUMMARY: Rapid fusion after contact between multinucleate, naturally synchronous plasmodia of the same strain of Physarum polycephalum was demonstrated by autoradiography. Fusion between plasmodia of equal size at the same stage in the mitotic cycle resulted in synchronous mitosis with a delay. This delay was slight if the nuclei were about to undergo mitosis at the time of fusion, but increased in a roughly linear fashion to about 4 h in plasmodia fused at an early stage in the mitotic cycle. Fusion between plasmodia at different stages in the mitotic cycle also resulted in synchronous mitosis, division of nuclei late in the cycle being delayed and of those early in the cycle being accelerated. When both plasmodia were in mid-interphase, the amount of acceleration was proportional to the difference in stages at the time of fusion, a 5 h phase difference giving about 3 h acceleration. However, non-synchronous mitosis resulted when a plasmodium about to undergo mitosis was fused with one earlier in the nuclear cycle, the nuclei in the former plasmodium presumably having reached a stage at which retardation could not occur.
-
-
-
The Physiological Role of Tetrathionate Respiration in Growing Citrobacter
More LessSUMMARY: The reduction of tetrathionate to thiosulphate by anaerobically growingCitrobacter caused a significant rise in specific growth rate and molar growth yield. It enabled alsoanaerobic growth on non-fermentable carbon sources and resembled therefore the respiratory reduction of nitrate to nitrite. The efficiency of energy production by tetrathionate respiration amounted to only two-thirds that of nitrate respiration.
-
-
-
Toxicity of Rubratoxin B to Fungi
More LessSUMMARY: The fungi Aspergillus flavus, A. niger, Penicillium expansum, Neurospora crassa, Cladosporium herbarum, Mucor spinosus and Rhizopus nigricans were cultivated (i) in malt extract solutions with various concentrations of rubratoxin B (100, 10, 1 μg/ml) in order to study the hyphal morphology and (ii) on filter discs containing different amounts of the same toxin (100, 10, 1 μg/disc) to detect any influence on sporulation. In the presence of 100 μg toxin/ml the hyphal tips of A. niger and A. flavus were very often swollen and much septate, or were transformed into giant cells. Plasmoptysis often occurred. The germ tubes of R. nigricans were much deformed. It is assumed that all these toxic effects were caused by weakening of the hyphal tips by interference with wall synthesis. Rubratoxin B (100 μg/disc) completely inhibited the sporulation of all of the fungi. Lower concentrations diminished sporulation of most of the fungi.
-
-
-
Effect of Pentachloronitrobenzene (PCNB) and Other Chemicals on Sensitive and PCNB-resistant Strains of Aspergillus nidulans
More LessSUMMARY: Pentachloronitrobenzene (PCNB)-sensitive and PCNB-resistant strains of Aspergillus nidulans were grown in liquid and on solid media with and without PCNB. On solid medium with PCNB, hyphae of the sensitive strain had thick walls, were shorter, branched less and had fewer nuclei per cell compared with the control. Under these conditions resistant hyphae were normal and less affected in growth parameters. In liquid medium the effect of PCNB on growth was less marked, but production of extracellular polysaccharide was decreased in the sensitive strain but not in the resistant one. The walls of resistant hyphae had a low hexosamine content compared with those of the wild-type; it increased in both by about a third in the presence of PCNB. Sodium deoxycholate had no effect on it. There was no difference in alkali-soluble material between the strains; it was decreased in both in the presence of PCNB, but more so in the sensitive than in the resistant strain. Changes in carbohydrate synthesis were a result of PCNB action on the sensitive wild-type; the resistant mutant withstood similar changes without such gross changes in morphology.
-
- 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
