-
Volume 119,
Issue 1,
1980
Volume 119, Issue 1, 1980
- Sgm Special Lecture
-
- Biochemistry
-
-
-
Effects of Temperature and Energy Inhibitors on Complex Formation between Escherichia coli Male Cells and Filamentous Phage fd
More LessThe effect of temperature and various energy inhibitors on the formation of a complex between Escherichia coli male cells and filamentous phage fd was studied by a novel filtration method. Centrifuged male cells were observed by electron microscopy to have lost the majority of pili and to produce complexes with fd only above 25 °C. After preincubation of the cells at 37 °C without addition of the phage, nearly half the level of complex formation observed at 37 °C was detected at 0 °C. Complex formation at various temperatures (0 to 37 °C) between cells preincubated at 37 °C and fd was at a minimum at about 20 °C. Several energy inhibitors and uncouplers drastically reduced complex formation at 37 °C, and also at 0 °C if the cells were briefly exposed to the reagents at the end of preincubation. Alteration of the cellular ATP concentration, either by shift-down of temperature or by the addition of the reagents, accompanied alteration in the ability of cells to form a complex with fd as well as alteration of the number of pili on the cell surface. In contrast to earlier reports, these results indicate that the complex formation between male cells and filamentous phage does not proceed either when pili disappear from the cell surface because of a decrease in the cellular energy level or when pili are removed by mechanical forces. The results also show that phage fd adsorption itself is not energy-dependent.
-
-
-
-
Aminopeptidase Activity of Acholeplasma laidlawii, Mycoplasma bovirhinis, Mycoplasma dispar and Mycoplasma bovis
More LessAminopeptidase activity was demonstrated in extracts of Acholeplasma laidlawii, Mycoplasma bovirhinis, M. bovis and M. dispar. The enzyme specificity, which differed amongst the mycoplasma species examined, was characterized using 19 aminoacyl-β-naphthylamides as substrates. The differences were detected after 4 h incubation with the substrates and potentially could be employed to aid in the characterization of certain mycoplasma species.
-
-
-
Major Outer Membrane Proteins: Common Antigens in Enterobacteriaceae Species
H. Hofstra and J. DankertThe major outer membrane (OM) proteins of 23 enterobacterial strains (principally clinical isolates) and five non-Enterobacteriaceae species were investigated by the sodium dodecyl sulphate-polyacrylamide gel immunoperoxidase (SGIP) technique to evaluate antigenic cross-reactivity among these proteins. All enterobacterial strains contained one or more peptidoglycan-associated major OM proteins, cross-reactive with the peptidoglycan-bound protein I of Escherichia coli, and one non-peptidoglycan-bound heat-modifiable protein, cross-reactive with protein II* of E. coli. Results indicated that antigenic cross-reactivity of the major OM proteins is a general phenomenon in the family Enterobacteriaceae, independent of any molecular weight variation of the corresponding proteins in different bacterial strains. SGIP experiments carried out with OM preparations of other species showed no cross-reactivity of any of their OM proteins with enterobacterial major OM proteins. The significance of the immunological relatedness of OM proteins for the classification of some Enterobacteriaceae is discussed.
-
-
-
The Orientation of Cytochromes in Membrane Multilayers Prepared from Aerobically Grown Escherichia coli K12
More LessCentrifugation of membrane vesicles, prepared from ultrasonically disrupted Escherichia coli K12, on to a planar surface followed by slow, partial dehydration results in a high degree of parallel orientation of the membrane planes with respect to each other and the supporting surface. Rotation of such membrane multilayers about a single axis parallel with the membrane planes within the magnetic field of an electron paramagnetic resonance (e.p.r.) spectrometer allows the orientation of anisotropic paramagnetic centres to be deduced. Computer simulations of the angular dependence of cytochrome e.p.r. spectra show two, or perhaps three, cytochromes, well-oriented with respect to the membrane plane. A low-spin cytochrome is oriented with the normal to its haem plane lying in the membrane plane. One (or perhaps two) high-spin cytochrome(s) lies with its haem plane making an angle of 45° with the membrane plane. The orientation of the low-spin cytochrome haem is thus the same as that of haems in b-type cytochromes and cytochrome oxidases of the a type found in the mitochondria of higher animal and microbial cells and the bacterium Paracoccus denitrificans ( Erecińska et al., 1979 ). The possible identity of this low-spin component as the terminal oxidase, cytochrome o, is discussed.
-
-
-
Purification of a Mucopolysaccharidase from Bacteroides distasonis
More LessA mucopolysaccharidase derived from a pathogenic strain of Bacteroides distasonis was isolated and purified by fractionation with cold acetone and ion-exchange chromatography on DEAE-cellulose, pH 8·0. Three detectable enzyme activities from concentrated supernatant filtrates were obtained in a fraction precipitated by three volumes of cold acetone; these were DNAase, hyaluronidase and chondroitinase-like activity. Separation of the DNAase was achieved by ion-exchange chromatography. Fractions designated as purified mucopolysaccharidase contained both hyaluronidase and chondroitinase-like activity.
-
- Development And Structure
-
-
-
Ultrastructural Changes in Escherichia coli Grown in Divalent Cation-deficient Medium
More LessEscherichia coli strains B and K12 could grow in very limiting conditions of divalent cation deficiency. Growth curves showed a long lag period of about 30 h, followed by an exponential phase bringing the bacterial concentration to about 107 ml−1, with a 24 min doubling time, while the growth curves of control cultures were characterized by short lag periods, maximum populations of about 109 ml−1 and an 18 min doubling time. The DNA/protein ratio in bacteria grown in deficient medium was 0·48 compared with 0·21 for control bacteria. Significant differences were found in the ultrastructure of the two types of bacteria. Freeze-etched control cells showed the typical appearance with the protoplasmic fracture face of the cytoplasmic membrane (PFC) having a random distribution of intramembranous particles. Bacteria growing in deficient medium in exponential phase presented several particle-free areas on the PFC. At the beginning of the stationary phase, the particle-free zones became larger and crystalline structures were formed. These structural modifications, which increased with culture age, were never observed in bacteria grown in control medium. Optical diffraction analysis of the crystalline structures in freeze-etched cells revealed regular periodic arrays with a rhomboid repeating unit approximately 7·6 × 5·4 nm in dimension and an angle between the axes of about 73°. Negative staining of isolated membranes of bacteria grown in deficient medium showed a more complex organization of the crystalline arrays, each unit being clearly composed of subunits.
-
-
- Ecology
-
-
-
Lysis of the Cyanobacterium Anabaena flos-aquae by Antibiotic-producing Fungi
More LessThe β-lactam antibiotic cephalosporin C has been extracted and partially purified from liquid cultures of the fungi Emericellopsis salmosynnemata and Acremonium kiliense. The ability of these and certain other fungi to lyse cyanobacteria is attributable to the production of this antibiotic. This is supported by the similarities, seen in light and electron microscopic preparations, of Anabaena flos-aquae cells exposed to pure cephalosporin C and to fungal exudates.
-
-
- Genetics And Molecular Biology
-
-
-
Isolation of Escherichia coli Mutants (cpdB) Deficient in Periplasmic 2′:3′-Cyclic Phosphodiesterase and Genetic Mapping of the cpdB Locus
More LessMutants of Escherichia coli deficient in the periplasmic enzyme 2′:3′-cyclic phosphodiesterase have been obtained. The gene, designated cpdB, was mapped by conjugation and transduction and found to be located about 0·11 min to the right of the cyc A locus on the E. coli genetic map.
-
-
-
-
Transductional Construction of an Isoleucine-producing Strain of Serratia marcescens
More LessStrain GIHVLr6426 was isolated as an isoleucine hydroxamate-resistant mutant from the wild-type strain of Serratia marcescens Sr41. This mutant had high activities of threonine deaminase and acetohydroxyacid synthase, both of which were insensitive to feedback inhibition. Genetic analysis revealed that strain GIHVLr6426 carried two regulatory mutations located in the ilv region. Strain T-693, a threonine-producing strain which was previously reported to carry four regulatory mutations for threonine biosynthesis, had an increased activity of acetohydroxyacid synthase. Transductional analysis revealed that one of the four mutations carried by strain T-693 was responsible for constitutive synthesis of both isoleucine and threonine biosynthetic enzymes. Strain T-803 was constructed by transferring the two mutations carried by strain GIHVLr6426 into strain T-693. The constructed strain had the six regulatory mutations for threonine and isoleucine biosyntheses, and produced about 25 mg isoleucine ml−1 in a medium containing sucrose and urea.
-
-
-
Somatic Segregation in Diploid Chlamydomonas reinhardii
More LessA double heterozygous arg-7-7 + /+ pab-2 diploid strain of Chlamydomonas reinhardii, phenotypically wild-type, was treated with N-methyl-N′-nitro-N-nitrosoguanidine. A total of 5500 colonies isolated on rich medium from the mutagenized cells were replicated to minimal medium. Nine auxotrophs (0·16 %) were isolated: six required p-aminobenzoic acid, two required arginine and one required both p-aminobenzoic acid and nicotinamide. On the basis of their cell volume, mating-type and DNA content, all the auxotrophs appeared to be diploids. However, analysis of crosses between the auxotrophs and the haploid wild-type strain suggested that the auxotrophs are probably aneuploids. This conclusion is also supported by the slow growth, heterogeneity in colony size and reduced pigmentation of certain of the auxotrophs cultivated on supplemented medium. The same conclusion is supported by control experiments in which 0·10 % auxotrophs were recovered. One auxotroph, however, apparently resulted from mitotic crossing-over at the four-strand stage. Under our experimental conditions, the mutagen does not seem to play a significant role in the induction of somatic segregation.
-
-
-
Characterization of Bacillus stearothermophilus Plasmid pAB124 and Construction of Deletion Variants
More LessA restriction endonuclease cleavage map of the tetracycline resistance plasmid pAB124, originally isolated from Bacillus stearothermophilus, was constructed using ten enzymes. Tetracycline resistance was associated with a 1·95 megadalton (Md) region of pAB124 lying between two EcoRI sites, and this region was circularized to produce a viable tetracycline resistance plasmid (pAB224), with two EcoRI fragments of pAB124 deleted amounting to 0·95 Md. A second plasmid (pAB524) with one EcoRI fragment (0·6 Md) of pAB124 deleted was also constructed. Restriction endonuclease cleavage maps of pAB224 and pAB524 were constructed.
-
-
-
Gene Transfer in Acinetobacter calcoaceticus: Fertility Variants of the Sex Factor pAV1
More LessThe naturally occurring transmissible plasmid pAV1 mediates chromosome transfer and can exhibit two distinct levels of transmissibility in Acinetobacter calcoaceticus strain EBF65/65. The two states of pAV1 have been arbitrarily designated pAV1a (low frequency variant) and pAV1b (high frequency variant). Both variants have the same incompatibility and host range properties and each mobilizes two non-transmissible resistance determinants for tetracycline and neomycin. Sex factor activity has been shown to be stable: however, pAV1b fertility variants can be derived from pAV1a donors following conjugal transfer of pAV1 into new recipient strains of EBF65/65.
-
-
-
DNA Restriction and Modification in Escherichia coli: Functional Analysis of the Role of the dnaC(D) Gene Product
More LessEscherichia coli strain PC-7 carries two independent temperature-sensitive mutations, one affecting the restriction and modification (R-M) phenotype and the other the DnaC(D) phenotype. The results of complementation and P1 transduction analysis of the mutation affecting the R-M phenotype implicate a fourth gene, designated hsdX, located close to the hsd three-gene complex. The properties of merodiploids constructed between appropriate recipients and F' elements with different mutations in hsdS, hsdR and hsdM genes might indicate that in strain PC-7 the temperature-sensitive products, determined by hsdR and hsdS K cistrons, are synthesized. The role of the temperature-sensitive dnaC(D) gene product in the formation of the restriction endonuclease was studied and no direct relation was found between the DnaC(D) and R-M phenotypes.
-
-
-
Isolation and Characterization of Glutamate Synthase Mutants of Azospirillum brasilense
More LessSix mutants of Azospirillum brasilense Sp6 unable to fix nitrogen have been isolated and characterized. Analysis of the enzymes involved in nitrogen metabolism has shown that the mutants are deficient in glutamate synthase activity (asm). They also have a low activity of glutamine synthetase and no or very low nitrogenase activity (assayed by acetylene reduction). In addition, the mutants were unable to grow on various sources of combined nitrogen such as nitrate, nitrite, alanine, histidine, adenine and xanthine.
-
- Immunology
-
-
-
Growth Medium Constituents Contaminating Mycoplasma Preparations and their Role in the Study of Membrane Glycoproteins in Porcine Mycoplasmas
More LessSeveral Mycoplasma and Acholeplasma species chosen at random and solubilized with sodium dodecyl sulphate showed a common periodic acidSchiff positive band with an apparent molecular weight of about 64000, when examined by polyacrylamide gel electrophoresis. Another more cathodic minor band was detected in M. hyopneumoniae and M. flocculare. The common periodic acid-Schiff positive band appeared when a precipitate of serum constituents of the uninoculated growth medium after incubation was examined. The minor band was identified as a serum glycoprotein contaminating mycoplasmas grown in the presence of swine serum. We draw attention to the compounds as a possible source of error in serological tests or in the lymphocyte stimulation response. After lithium diiodosalicylate solubilization and aqueous phenol extraction, polyacrylamide gel electrophoresis showed a periodic acidSchiff positive band in membranes from M. hyopneumoniae (molecular weight 75000) and M. hyorhinis (molecular weight 80000), suggesting the presence of a membrane glycoprotein. Such a glycoprotein was absent from A. granularum. Since the common periodic acidSchiff positive band was not extracted by aqueous phenol, this growth medium constituent did not contaminate the preparations of membrane glycoproteins. However, the minor band was present in glycoprotein preparations of M. hyopneumoniae grown in the presence of swine serum.
-
-
- Medical Microbiology
-
-
-
Primary Antimitochondrial Activity of the Cancer Drug Methylglyoxal Bis(guanylhydrazone) in Yeast Cells
More LessPrimary action of methylglyoxal bis(guanylhydrazone) (MGBG) on the yeast mitochondrial system was demonstrated by (1) selective inhibition of cell growth in non-fermentable medium, (2) blockage of mitochondrial synthesis of cytochromes aa3 and b and (3) ultrastructural aberration. The drug caused extensive deletions in mitochondrial DNA detected by an increase in the frequency of the mitochondrial mutant petite but had little or no effect on cell viability. Growth inhibition by MGBG was antagonized by spermidine but neither the polyamine nor MGBG had any effect on growth inhibition by ethidium bromide. Strains showed no cross-correlation in their tolerance to MGBG and ethidium bromide.
-
-
-
-
The Preparation and Partial Characterization of Antigenic Fractions Obtained from the Mycelial Walls of Several Aspergillus Species
More LessExtracts with immunological activity were prepared from Aspergillus fumigatus, A. flavus, A. terreus, A. niger and A. nidulans. In each case crude mycelial wall was extracted with an aqueous solution of Triton X-100 giving detergent-soluble material. Further fractionation was achieved by removing the detergent from this solution; the resultant precipitate was removed by centrifugation, and the aqueous supernatant was used as a source of soluble antigens. The sensitivity of these preparations was compared with that of water-soluble antigenic material, prepared from whole macerated mycelium, by double diffusion and counterimmunoelectrophoresis using homologous antisera and sera from patients suffering from aspergilloma and allergic bronchopulmonary aspergillosis. The selectivity of these antigenic preparations was monitored with heterologous antisera raised in rabbits. Batch variability was analysed for one strain of A. fumigatus using chemical and immunological methods. The nature of the antigenic sites involved in these reactions was investigated by studying the susceptibility of the preparations to proteolytic hydrolysis, periodate oxidation and concanavalin A treatment. The total protein and carbohydrate content of each fraction was determined and the constituent sugars analysed in an attempt to correlate chemical composition with antigenic activity.
-
-
-
The Cohesive Properties of Variants of Neisseria gonorrhoeae Strain P9: Specific Pilus-mediated and Non-specific Interactions
More LessThe cohesive properties of virulent pilated Neisseria gonorrhoeae strain P9 (P++) have been compared with those of a non-pilated isogenic variant (P−) possessing the same outer membrane components. The binding of P++ gonococci to buccal epithelial cells was dependent on pH, with an optimum at pH 6·5 to 7·0. This adhesion was markedly inhibited by treatment of the buccal epithelial cells with a neuraminidase/exoglycosidase mixture. In contrast, the binding of P++ gonococci to erythrocytes was unaffected by pH. A possible explanation is that pili bind to a carbohydrate receptor present on buccal epithelial cells but lacking on erythrocytes. The adhesion of P− gonococci to erythrocytes and to buccal epithelial cells was unaffected by pH but enhanced by treatment of the cells with neuraminidase or periodate. Presumably, neuraminic acid residues on host cell surface carbohydrates inhibit adhesion. The finding that P− gonococci bind to amphipathic gels suggests hydrophobic interactions as a possible non-specific mechanism attaching P− gonococci to host cell surfaces.
-
-
-
Importance of Antiserum and Phagocytic Cells in the Protection of Mice Against Infection by Klebsiella pneumoniae
More LessRabbit antiserum to Klebsiella pneumoniae showed a powerful protective effect against intramuscular infection in normal mice. No protective effect was observed in mice whose monocytes and polymorphonuclear cells were depleted by X-irradiation. The antiserum had approximately the same protective effect in mice whose macrophages were blocked selectively by carrageenan as in normal mice. It is concluded that antiserum exerted its effect by opsonic function and that opsonized K. pneumoniae were eliminated mainly by polymorphonuclear cells rather than macrophages, at least in an early phase of the infection. These findings were supported by histological examination and observation of intracellular killing in vitro.
-
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
