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Volume 72,
Issue 3,
1972
Volume 72, Issue 3, 1972
- Biochemistry
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Permeability of Dictyostelium discoideum towards Amino Acids and Inulin: a Possible Relationship between Initiation of Differentiation and Loss of Pool Metabolites
More LessSUMMARY: The permeability of Dictyostelium discoideum amoebae towards amino acids and inulin was studied under conditions suitable for development of aggregation-competence and in thick cell suspensions. During the pre-aggregation period, the amoebae released large amounts of amino acids and nucleotides into the suspending medium. The uptake of glutamate and lysine by amoebae was passive, but inulin was taken up actively, probably by pinocytosis. Hence the simplest explanation for leakage of metabolites is that the amoebae have no active mechanism for retaining them. A possible relationship between initiation of differentiation and loss of pool metabolites is discussed.
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Carbon Assimilation Pathways during Growth of Pseudomonas AM1 on Methylamine and Pseudomonas MS on Methylamine and Trimethylsulphonium Salts
More LessSUMMARYA study was made of the incorporation of carbon from [14C]methylamine by cultures of Pseudomonas AMI growing on methylamine. The distribution of radioactivity within the non-volatile constituents of the ethanol-soluble fractions of the bacteria, after incubation for periods of up to 38 s, was analysed by chromato-graphy and autoradiography. Most of the radioactivity fixed at the earliest times of sampling appeared in serine, phosphorylated compounds and malate. These results contrasted with previous studies of the incorporation of labelled growth substrates by cultures of Pseudomonas MS growing on methylamine or trimethyl-sulphonium salts and correlated with the specific activities of hydroxypyruvate reductase, phosphoenolpyruvate carboxylase, N-methyl glutamate synthetase and γ-glutamylmethylamide synthetase in bacterial extracts. No hydroxypyruvate reductase was detectable in extracts of Pseudomonas MS grown either on methylamine or on trimethylsulphonium nitrate. The assimilation pathway for methylamine in Pseudomonas AMI appears essentially the same as that for methanol and different from that in Pseudomonas MS.
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Effect of Aerosolization on the Transport of α-Methyl Glucoside and Galactosides into Escherichia coli
More LessSUMMARY: Aerosolization decreased the accumulation of methyl-[α-D-gluco]pyranoside (αMG) in two strains of Escherichia coli. The inactivation was apparently not due to damaged permeases but to detachment from the bacteria of components involved in the transport of substrates through bacterial membranes. Transport activity was partially restored when aerosolized bacteria were incubated with leaked components. Aerosolization also decreased accumulation of isopropyl-thio-β-D-galactopyranoside (IPTG) by E. coli but increased permeability to O-nitrophenyl-β-D-galactopyranoside (ONPG). Loss in viability of airborne bacterial populations correlated with the decrease in αMG accumulation by bacteria recovered from aerosols one second after generation of the cloud.
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- Development And Structure
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Fine Structure of Protoplasts of Aspergillus nidulans
More LessSUMMARY: Observations on the ultrastructure of Aspergillus nidulans protoplasts obtained by treatment of mycelium with Streptomyces RA lytic enzyme show that they were free of wall material. The preparations contained two types of protoplasts, released at different times during the lytic enzyme-mycelium incubation. Those released first contained small vesicles and a high density of ribosomes. The type released later had large vacuoles and fewer ribosomes. It is suggested that these differences reflect the hyphal location and origin of the protoplasts.
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- Genetics And Molecular Biology
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A Mitochondrial Mutant of Coprinus lagopus
More LessSUMMARY: A mutation in Coprinus lagopus, designated acu-10, led to inability to use acetate as sole carbon source for growth. Using both somatic segregation and non-Mendelian segregation at meiosis as criteria, the mutation was shown to be inherited cytoplasmically. The mutant has a cytochrome spectrum in which the α peak for cytochrome a is absent and a new peak is present when compared to wild-type, corresponding to cytochrome a 1. Using the acu-10 mutation as a cytoplasmic marker, it has been possible to demonstrate that the migration of nuclei which occurs during dikaryotization takes place independently of any general movement of organelles. It is unlikely, therefore, that nuclear migration is brought about by cytoplasmic streaming.
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R Factors from Proteus rettgeri
More LessSUMMARY: Of 12 R factors transferred from wild strains of Proteus rettgeri to Escherichia coli K12, all were fi - Five were of the N-compatibility group; three belonged to a newly defined group T, of which Rts1 is the prototype; one belonged to group W. The other three constituted at least one compatibility group, not previously described. The replication of two of the T plasmids, like that of Rts1, was temperature sensitive. This set of R factors is significantly different from those derived from bacteria of other genera.
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- Medical Microbiology
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Electrophoretic Patterns of Strains of Mycoplasma pulmonis
More LessSUMMARY: Strains of Mycoplasma pulmonis, examined by polyacrylamide-gel electrophoresis of proteins extracted in a phenol-acetic acid-water solvent, gave patterns with reproducible differences. Some strains could be placed into groups, but a number could not be associated with any group. In all but one case a ‘basic M. pulmonis pattern’ was easily recognizable. This exception suggests that occasionally one might fail to recognize a strain of M. pulmonis by relying solely on the electrophoretic technique.
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Serological Heterogeneity of Mycoplasma pulmonis
More LessSUMMARY: Twelve stock and 15 freshly isolated strains of Mycoplasma pulmonis were examined and compared using four serological techniques. Complement fixation tests and inhibition of growth on solid medium showed that the strains were all M. pulmonis, although, with some strains, only one of these techniques gave an unequivocal result. These tests were confirmed to be specific only at a species level. Gel diffusion and metabolic inhibition techniques revealed heterogeneity of the strains at the subspecies level. The relationship between some strains was statistically significant and stable in vitro and some small groups could be defined.
These serogroups bore no relationship to groups formed on the basis of protein patterns produced on polyacrylamide gel electrophoresis of strains of Mycoplasma pulmonis.
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- Physiology And Growth
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Inhibition of Flagellum Morphogenesis in the True Slime Mould Didymium nigripes
More LessSUMMARY: Flagellum morphogenesis in the slime mould, Didymium nigripes, involves a sequence of events during which amoebae are changed into biflagellated cells; in a population of cells this transformation is nearly synchronous. In the present study a series of inhibitors thought to inhibit RNA and protein synthesis and microtubule assembly were added in an attempt to characterize the macromolecular events associated with this amoebo-flagellate transformation.
High concentrations of acriflavin and proflavin (50 μg/Uml) and lower concentrations of cycloheximide (5 to 10 μg/ml) blocked the morphogenetic process completely. Other reported inhibitors of RNA synthesis and microtubular assembly delayed the onset of flagellum formation for varying periods of time dependent upon the concentrations employed.
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Flagellum Growth and Regeneration in the True Slime Mould Didymium nigripes
More LessSUMMARY: The kinetics of flagellum elongation during flagellum morphogenesis were investigated in the slime mould, Didymium nigripes. Growth rate varied at different temperatures. Long and short flagella elongated at independent rates and exhibited their maximum rates of elongation at different times. Limitation on final length did not seem to be a function of the precursors available for flagellum synthesis. Growth kinetics of normally growing and regenerating flagella and of amoebae previously exposed to cycloheximide suggest that control of growth rate is not merely a function of flagellum length or the diffusion of precursors to the assembly site.
The effect of cycloheximide and streptomycin on flagellum growth were compared in both morphogenetic and regenerating systems. Addition of cycloheximide to a growing or regenerating system immediately halted flagellum elongation. Amoebae exposed to cycloheximide, washed free of the drug and then incubated under standard conditions showed abnormal growth kinetics and reduced final flagellum length; these observations suggest some residual effect of this drug. Streptomycin delayed the morphogenetic process but did not affect flagellum length once morphogenesis occurred.
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Changes in Total Soluble Proteins and in Some Enzymes during Morphogenesis of Sclerotium rolfsii
I. CHET, NIRA RETIG and Y. HENISSUMMARY: Patterns of soluble proteins and enzymes were studied in the normal mycelium of the fungus Sclerotium rolfsii and at three stages of sclerotial formation. Significant changes in total soluble proteins were found during the morphogenetic process, as detected by gel isoelectric focusing. While no changes could be detected in acid phosphatase activity, peroxidase activity was higher in mature sclerotia than at other stages. Polyphenol oxidase activity was demonstrated with dihydroxy-phenylalanine, catechol and tyrosine as substrates. While only one active isozyme of the latter enzyme was found in the mycelium, six different isozymes were detected in the mature sclerotia. Esterase isozymes, on the other hand, decreased significantly during morphogenesis.
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Properties and Comparative Starch-gel Electrophoresis of Megacins from Several Bacillus megaterium Strains
More LessSUMMARY: The products of several megacinogenic strains of Bacillus megaterium were analysed by starch-gel electrophoresis. All were mixtures of inhibitors, among which megacins A, C and Cx could be distinguished. Several non-inducible megacins were produced in liquid medium and they seemed to be a heterogeneous group which may correspond to ‘megacin B’. The effects of heat and proteolytic enzymes on megacins were investigated and the molecular weights of several megacins were estimated by chromatography using Sephadex G 200. The molecular weight of crude megacin C was about 153000. Strains producing megacins C and Cx could be ‘cured’ by growth at 43°C. Megacins C and Cx were released from the surface of meg+ organisms by partial digestion of the wall with trypsin or lysozyme.
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Accumulation of Urea and Allantoin during Purine Utilization by Germinating Spores of Geotrichum candidum
More LessSUMMARY: Urea and allantoin were accumulated by germinating spores of Geotrichum candidum in the presence of xanthine, uric acid or allantoin. The concentration of endogenous allantoin was 5 to 10 times higher than that of urea. The specific activities of uricase and allantoicase were increased about nine-and fivefold respectively by uric acid and allantoin. No induction of allantoinase and ureidoglycolase was detected. Results may suggest that the different levels of purine degradative enzyme during induction might favour allantoin accumulation and prevent urea from attaining a toxic concentration.
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Melanin Production by Aspergillus nidulans in Batch and Chemostat Cultures
More LessSUMMARYIn batch culture melanin production by Aspergillus nidulans occurred after the cessation of exponential growth. Melanin production in the chemostat was favoured when the growth rate was a relatively small fraction of the maximum growth rate under the prevailing culture conditions. Growth-limitation by the carbon source induced melanogenesis more strongly than did growth-limitation by the nitrogen source. Melanin production was maximal within the dissolved oxygen tension range 16 to 30 mmHg; it increased with temperature in the range 20 to 37°C and with increase in pH up to 7.9. At high temperature and high pH the ability to produce melanin declined. The melanin was variable in composition. Both soluble and insoluble forms were produced. The soluble form appeared to be less highly polymerized than the insoluble form which was laid down on the hyphal walls and had a microfibrillar structure revealed by the electron microscope.
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- Short Communication
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- Taxonomy
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A Numerical Taxonomic Study of Streptococci of Serological Group D
More LessSUMMARYThe results of 45 biochemical and physiological tests on 122 strains of streptococci of serological group D (three of which also contained the ‘Q’ antigen) from a variety of habitats were subjected to computer analysis. The organisms clustered into five main groups representing the species (1) Streptococcus faecalis, (2) S. faecium and S. durans, which we consider are best treated as one species, and (3) S. aviun, (4) S. bovis, (5) S. equinus.
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The Taxonomy of the Crown-gall Organism Agrobaterium tumefaciens and Its Relationship to Rhizobia and Other Agrobacteria
More LessSUMMARYStrains of agrobacteria, rhizobia and other organisms were collected from various sources and tested for their ability to utilize 61 compounds as sole carbon sources, oxidative or fermentative glucose metabolism, hydrolysis of starch, casein and gelatin, anaerobic arginine metabolism and production of 3-ketolactose. The resulting data was used in a numerical analysis and the strains were grouped on the basis of overall similarity.
The resultant groupings confirmed the idea that the genera Agrobacterium and Rhizobium be combined, and four species of fast-growing rhizobia were recognized: Group I, Rhizobium radiobacter; Group II, Rhizobium meliloti; Group III, related to Agrobacterium rhizogenes and the Biotype 2 strains of Keane, Kerr & New (1970); Group IV, Rhizobium leguminosarum. Crown-gall organisms were associated with groups I and III. The four species were defined without reference to pathogenicity or nodulating ability and it appears at present that crown-gall organisms can only be distinguished by pathogenicity testing.
Agrobacterium rubi H36 probably belongs in the genus Rhizobium whereas Agrobacterium gypsophilae 1948 and Agrobacterium pseudotsugae 180 do not.
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