- Volume 67, Issue 1, 1971
Volume 67, Issue 1, 1971
- Biochemistry
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Immunological Comparisons of Histidinol Dehydrogenases
More LessSummary: Partially purified histidinol dehydrogenases from a variety of micro-organisms have been tested with antibodies prepared in rabbits to pure histidinol dehydrogenases (HD enzymes) from Neurospora crassa (NHD) and Salmonella typhimurium (SHD). Cross-reactions using the double diffusion technique were demonstrated only between the pairs N. crassa and Aspergillus nidulans and S. typhimurium and Escherichia coli. The dehydrogenation of histidinol by S. typhimurium and N. crassa was inhibited by their respective antibodies and antibody to NHD inhibited HD enzymes from A. nidulans, Penicillium chrysogenum, Chlorellapyrenoides and spinach in decreasing effectiveness. Antibody to SHD inhibited HD from S. typhimurium, E. coli, and Micrococcus lysodeikticus to approximately the same degree and from Bacillus subtilis to a lesser degree. HD activity from Pseudomonas aeruginosa, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Arthrobacter histidinolovorans and Euglena gracilis was affected by neither of the antibodies.
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Bicarbonate Fixation by Cell-free Extracts and by Mycelium of Neocosmospora vasinfecta
More LessSummary: The most active carboxylating enzyme in cell-free extracts of Neocosmospora vasinfecta was identified as pyruvate carboxylase (EC 6.4.1.1) on the basis of its substrate specificity, biotin dependence and cofactor requirements. Following 48 h. growth on acetate as sole carbon source, the specific activity of the extracted enzyme was 1·4 to 3 times greater than when the organism was maintained on glucose. Bicarbonate fixation in vivo was considerably reduced in the acetategrown mycelium, but was enhanced when ethyl pyruvate was supplied. The mycelial pyruvic acid content was almost an order of magnitude lower in acetategrown mycelium than in glucose-grown. These results indicate that bicarbonate fixation in acetate-grown mycelium may be limited by the availability of pyruvic acid.
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Some Properties of the Naphthalene Oxygenase from Pseudomonas sp. NCIB 9816
More LessSummary: Extracts of Pseudomonas sp. NCIB 9816, grown on naphthalene as sole carbon source, oxidized a number of polycyclic aromatic hydrocarbons in the presence of NADH. The ability of the extracts to oxidize naphthalene in the presence of either NADH or NADPH was rapidly destroyed in air and upon dilution or dialysis but was restored by various reducing agents, in particular sodium borohydride and dithioerythritol. Because of its instability only a twofold purification of naphthalene oxygenase was obtained. On the basis of its behaviour it is proposed that naphthalene oxygenase is an NAD(P) H-dependent dioxygenase with tightly bound Fe2+ ions.
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- Ecology
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The Physiological Ecology of Cyanidium caldarium
More LessSummary: The distribution and physiology of Cyanidium caldarium in its natural habitat in acidic hot springs and hot soils have been studied. This eucaryotic alga was the sole photosynthetic organism in habitats with pH less than 5 and temperatures greater than 40°. The upper temperature limit of the alga was 55° to 56° and the optimum temperature for growth was 45°. Temperature strains such as are found in blue-green algae of alkaline thermal habitats were not found for Cyanidium caldarium. In aquatic habitats the lower temperature limit was about 35° to 36°, the organism apparently being unable to compete at temperatures below this with other algae. In soils the alga was found at temperatures as low as 10°, apparently because in terrestrial habitats competition with other algae was less significant. The pH range at which the alga has been found in nature was from 0·05 to 5·0 and growth in culture occurred over this whole range. The optimum pH for growth was between 2 and 3. In nature the alga was found in habitats of widely varying light intensity, up to 7000 ft-candles. The alga became adapted to reduced light intensity by increasing its photopigment concentrations. Photosynthesis in populations adapted to reduced light intensities was inhibited by high light intensities. The alga grew well on glucose in the dark, and the concentration of photosynthetic pigments was reduced. When such bleached cells were transferred to the light in the presence of glucose, pigments were not synthesized and heterotrophic growth continued; when glucose was omitted, pigment synthesis occurred and photosynthetic growth resumed. Glucose did not inhibit pigment synthesis when added to cells growing in the light.
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- Genetics And Molecular Biology
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Effect of γ-Radiation on the Donor Ability of recA and recA + Strains of Escherichia coli
More LessSummary: The sensitivity to γ-radiation of the chromosome of a recA + Hfr strain of Escherichia coli was six times greater when assayed by donor ability in conjugation than when assayed by survival in unmated bacteria. With a recA Hfr strain sensitivities were comparable when assayed by the two methods, and were similar to the sensitivity of donor ability in the recA + strain. We suggest that the greater resistance of survival in the recA + strain may be due to a post-replicational repair process which does not occur in the recA strain and which is prevented from occurring when a chromosome of either strain is involved in conjugation. When a recA Hfr and a recA F- strain were given 8·5 krads γ-radiation, enough to inhibit completely normal DNA synthesis, the DNA synthesis associated with conjugation still occurred. This suggests that the lesions which prevent recombinant formation may act not by inhibiting chromosome transfer, but by affecting a later stage in the process of integration.
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Citrobacter freundii Mutants Deficient in Host Specificity Functions and Their Recipient Ability for Foreign Deoxyribonucleic Acid
More LessSummary: The isolation and properties of mutants of Citrobacter freundii deficient in host specificity functions is described. Two mutant types have been isolated, one deficient in restriction (hsr) and another one deficient in both restriction and modification (hss). These non-restricting mutants are good recipients for plasmid DNA in conjugation experiments with Escherichia coli donor strains. Transfer of chromosomal markers was observed in crosses between E. coli Hfr strains and non-restricting mutants of C. freundii, and in crosses between Salmonella typhimurium Hfr or S. abony Hfr strains and non-restricting C. freundii recipients. Recombinants from these crosses are unstable, partially diploid strains.
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A Temperature-sensitive Cell Division Component in a Mutant of Salmonella typhimurium
More LessSummary: Salmonella typhimurium strain 4 a is temperature-sensitive. It grows normally at 25° but stops dividing immediately when shifted to 42°. After the shift cell mass increases at a normal rate and DNA synthesis is unaffected. Viable count remains constant for about 3 h. and then falls off sharply. The filaments formed at 42° divide when returned to 25° after a delay which in broth is about 70 min. This delay is not markedly dependent on the time previously spent at 42° but is mediumdependent, being shorter in enriched media. Eventually all the divisions prevented at 42° take place at 25°. Chloramphenicol almost completely stops filament septation and division, and when added early in the recovery period causes fragility, some lysis and a sharp fall in viable count. Nalidixic acid does not stop filament division. It is concluded that a shift to 42° influences cell division directly by causing the irreversible inactivation of a component required at a late stage of division. The length of the division recovery period when filaments are returned to 25° suggests that the component must accumulate throughout most of the division cycle before division can restart.
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- Medical Microbiology
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Nutritional Requirements of Streptococcus salivarius
More LessSummary: The nutritional requirements of Streptococcus salivarius ATCC 13419 were studied. Ammonia could serve as the major nitrogen source in a medium containing glucose, cysteine, nicotinic acid, biotin. thiamin, riboflavin, pantothenic acid and inorganic salts. Streptococcus salivarius NCTC8618 and 11 oral isolates of S. salivarius grew in this medium. For growth of S. salivarius ATCC9759 the medium had to be supplemented with glutamic acid. The cysteine requirement of S. salivarius ATCC13419 could be replaced by cystine, homocysteine, homocystine or thiosulphate. Urea could be used as nitrogen source by S. salivarius ATCC13419, S. salivarius ATCC9759 and by five of the 11 oral isolates of S. salivarius.
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- Physiology And Growth
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Thermally-induced Explosive Migration of Paramecium
More LessSummary: In the course of developing methods to obtain dense populations of the ciliated protozoon Paramecium aurelia with undisturbed physiology and free from growth medium, attempts were made to elicit a positive phototactic response. No phototaxis was observed, but a dramatic positive thermotaxis was demonstrated. When a dilute buffer was layered over the more dense culture fluid and a thermal gradient induced, the ciliates first collected at the buffer/culture fluid interface and then moved explosively through it to the top of the buffer layer. Concentrations of 105 organisms/ml. were obtained.
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Influence of Oxygen Concentration on the Colony Type of Derxia gummosa Grown on Nitrogen-free Media
More LessSummary: At oxygen concentrations of less than 0·2 atm. Derxia gummosa formed only the ‘massive’ colony type on nitrogen-free agar media; the ‘thin’ colony type which predominates in air was absent. Only the ‘massive’ colonies reduced acetylene. The acetylene-reducing activity of samples from a nitrogen-fixing continuous culture was inhibited when the oxygen supply was increased, which suggests that the oxygen sensitivity previously reported during growth in nitrogen-free media is associated with the nitrogen-fixing process. Colonial dimorphism probably arises because only when the local oxygen concentrations on the agar surface are depressed can nitrogen fixation and subsequent growth to the ‘massive’ colony type take place.
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- Taxonomy
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Sense and Nonsense in Bacterial Taxonomy *
More LessSummary: Classifications cannot be final, and the same group of organisms may be sorted and arranged in many different ways. The species is man-made, and since it cannot be defined the creation of taxa of higher categories based on species makes an absurd situation. The type method (a nomenclatural device) is inapplicable to bacteriology, and more use should be made of the population concept.
Bacteriological nomenclature is full of absurdities, many derived from the Botanical Code. In particular, the principles of priority and the retroactive application of new rules are criticized, especially when they are applied to the names of well-established taxa.
Two new principles of heretical taxonomy are described.
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Bacillus acidocaldarius sp.nov., an Acidophilic Thermophilic Spore-forming Bacterium
More LessSummary: Fourteen cultures of thermophilic acidophilic bacteria have been isolated from a variety of thermal acid environments by enrichment at elevated temperatures and low pH. Morphological and physiological properties suggest that the bacteria are members of a homogeneous group of aerobic spore-forming rods. The base composition of the DNA is about 62 % guanine plus cytosine, and this fact together with the physiological properties suggests that relationship to other species in the genus Bacillus is rather distant. The isolates are hence classified in a new species, Bacillus acidocaldarius.
The species is characterized by the ability to grow at temperatures from 45° to 70° (optimum 60° to 65°) and at pH values from 2·0 to 6·0 (optimum 3 to 4).
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Taxonomy of the Clostridia: Wall Composition and DNA Homologies in Clostridium butyricum and Other Butyric Acid-producing Clostridia
More LessSummary: Strains designated as Clostridium butyricum were found to constitute two distinct groups on the basis of wall sugar patterns, nucleotide-sequence similarities of DNA preparations and nutritional requirements. Organisms in homology group I had walls which contained only glucose and would grow in a mineral salts-glucose medium with 0·05 μg./ml. biotin, although growth was improved by the addition of amino acids. Some strains labelled C. multifermentans and C. fallax belonged to this group. Organisms in homology group II had glucose and galactose as wall sugars and would not grow in mineral salts-glucose medium with amino acids and 10 vitamins unless yeast extract was also added. Strains of C. amylolyticum, C. rubrum, C. beijerinckii, C. lacto-acetophilum and some strains labelled C. multifermentans belonged to group II.
It is recommended that the name Clostridium butyricum be retained for the organisms in group I, while C. beijerinckii is suggested for group II. Some of the strains labelled C. fallax and the strains of C. acetobutylicum, C. aurantibutyricum, C. pasteurianum and C. tyrobutyricum did not belong to either group.
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The Amino Acid-fermenting Clostridia
More LessSummary: Representative strains of 30 named species of clostridia were tested for their ability to grow in a semidefined medium containing either 1 % (w/v) glucose or 3 % (w/v) acid-hydrolysed casein as an energy source. Strains from 15 species were selected empirically as amino acid-fermenting types by comparing growth in the two media. After growth in 3 % casein hydrolysate medium the organisms were removed and their amino acid utilization determined by examining the culture supernatants. The organisms were then divided into four main groups. The characteristic features of each group are as follows: group I, the utilization of proline with the production of δ-amino valeric acid; group II, mainly arginine and/or glycine utilized; group III, the utilization of glutamic acid, serine and histidine; group IV, serine and threonine utilized. Possible implications of these findings for the taxonomy of clostridia are discussed.
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Volumes and issues
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Volume 170 (2024)
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