摘要:

Cell-free extracts ofXanthomonas phaseolicontain the individual enzymes of the tricarboxylic acid cycle, and it is suggested that this is the main pathway for the terminal oxidation of carbohydrate in this organism.X.phaseolican grow on a medium containing acetate as the sole source of carbon. Cell-free extracts of such acetate-grown organisms contain the enzymes of the glyoxylate cycle, and it is concluded that the operation of this cycle permits the initial stages of synthesis of complex cell material from acetate at a rate sufficiently high to account for the observed rate of growth on the acetate medium. The two enzymes required to modify a tricarboxylic acid cycle into a glyoxylate cycle are present in very small amounts (malate synthetase) or absent entirely (isocitritase) in extracts of glucose-grownX.phaseoli.

ISSN:0008-4166    

DOI:10.1139/m59-001

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The growth of pure cultures ofDutialiella euchlorastrains WHOI-1 and WHOI-2,Platymonas subcordiformis,Phaeodactylum tricormitum,Chlorella vulgaris, andCyclotella meneghinianawas compared in two enriched sea water media and two artificial marine media. Three general patterns of growth were observed; the green flagellates grew the same in all media,PhaeodactylumandChlorellagrew more slowly in the artificial media, andCyclotelladid not grow in the artificial medium without organic supplements. The addition of vitamin B12to the artificial medium promoted good growth ofCyclotella, and of the species studied this alga was the only auxotroph. Growth in the enriched sea water medium was not affected by a precipitate, but removal of the precipitate markedly affected the rate of growth and the total number of cells obtainable.

ISSN:0008-4166    

DOI:10.1139/m59-002

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Mutants of phage T2, of the group calledrII mutants, are known to lack the parent phage's ability to form plaques on strains ofEscherichia colilysogenic for phage λ That they are capable of initiating desoxyribonucleic acid synthesis in the infected lysogenic host cells but are incapable of maintaining it has been shown by the present study using T2r7and -E.coliC112 (λs). In contrast with the superficially similar behavior shown by some other phages (e.g. λv1h), ultraviolet irradiation and consequent induction of the lysogenic culture do not release the prophage-linked inhibition of T2r7DNA synthesis. Net ribose-nucleic acid synthesis is stopped in all cultures on infection with T2r7.

ISSN:0008-4166    

DOI:10.1139/m59-003

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Cells ofMicrococcus halodenitrificansgrown in media containing more than 0.7 Msodium chloride appeared normal microscopically, but in 0.6 Msalt many cells were swollen and in 0.55 Msalt most cells were swollen or ruptured. The swollen cells were sensitive to osmotic shock. Calcium or magnesium prevented the cells from swelling and extended the lower limit of growth from 0.55 to 0.3 Msalt. Walls of normal cells contained 6 carbohydrates and 16 amino acids. Qualitative chromatographic analyses indicated that cells grown in 0.55 Msalt contained less tyrosine, diaminopimelic acid, and an unknown ninhydrin-positive, cytoplasmic component than cells grown in 1.0 Msalt. Quantitative estimates indicated that diaminopimelic acid/nitrogen ratio in cells decreased gradually from 0.25 to 0.16 as the salt content of the growth medium decreased from 1.0 to 0.55 M, but that it decreased to 0.003 in cells grown in 0.3 Msalt plus calcium. The results suggest that less cell wall material is produced as the salt concentration in the growth medium is decreased and that calcium has a protective effect on the weakened cells or protoplasts.

ISSN:0008-4166    

DOI:10.1139/m59-004

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The presence of a polyphenoloxidase in wheat stem rust uredospores has been demonstrated. The enzyme was released by the germinating spores together with phenolic substrates, resulting in the formation of phenol oxidation products in the surrounding medium. The substrate specificity of the enzyme was investigated, and gallic acid was found to give an unusually high oxidation rate. Pyrogallic acid and catechol were also rapidly oxidized. Toxicity tests have been carried out with phenol oxidation products on germinating spores and it has been shown that toxicity depends on the stage of oxidation. Short-term oxidations led to the formation of highly toxic compounds; longer periods of oxidation converted these into harmless products, whereas very long periods of oxidation resulted again in the production of toxic substances. The spores also contained a quinone reductase which apparently holds the phenolics in a reduced state until they are released during germination or during the infection process. The possible role of the phenol – phenoloxidase – quinone reductase system in the host–parasite relations of the wheat – stem rust complex is discussed.

ISSN:0008-4166    

DOI:10.1139/m59-005

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The lactic dehydrogenase ofHalobacterium salinariumis unstable and inactive at low solute concentrations. The irreversible loss of activity at low solute concentrations is a first-order reaction, the rate of which decreases with the second or third power of the salt concentration. The enzyme is protected to varying degrees by a variety of inorganic salts and by glycerol or glucose. Potassium chloride and glycerol also protect the enzyme against inactivation by urea.The enzyme is most active in the presence of potassium chloride, but several other salts are effective to varying degrees as activators. The activation is of the third or fourth order with respect to sodium or potassium chloride concentration. Potassium chloride decreases the affinity of the enzyme for its substrate. Glycerol does not activate the enzyme, but increases its activity in the presence of potassium chloride.It is suggested that this enzyme differs from enzymes of non-halophilic organisms in being less firmly held in its native catalytically active conformation. At low salt concentrations the electrostatic repulsion between ionized groups on the enzyme expands it to a form which is not catalytically active and which can readily expand further to an irreversibly denatured form.

ISSN:0008-4166    

DOI:10.1139/m59-006

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The utilization of glucose by proliferatingPenicillium digitatumcells has been examined by the radiorespirometric method. Glucose is catabolized by this organism mainly (77%) by way of the Embden–Meyerhof–Parnas pathway in conjunction with the tricarboxylic acid cycle and CO2fixation processes. A minor portion (23%) of the administered glucose is utilized via an oxidative route involving a C1–C5cleavage. Pathway estimations on the basis of CO2production and glucose consumption were also discussed.

ISSN:0008-4166    

DOI:10.1139/m59-007

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Microbiological analyses were conducted on unsterilized ground wheat seed, on the emerging primary root, 3 days following planting in soil and at 3-day intervals thereafter for a period of 17 days. By the third day following planting there were more than twice as many bacteria in the rhizosphere soil as in the control soil. Qualitative differences were apparent at this time also in that methylene-blue-reducing bacteria, ammonifiers, denitrifiers, gelatin-liquefying and starch-hydrolyzing types were preferentially stimulated. Studies with individual isolates obtained from samples taken even on the third day showed that rhizosphere population was more active than the soil population in regard to growth rate in different media. All effects mentioned were maintained and in some cases exaggerated with growth of the plant.

ISSN:0008-4166    

DOI:10.1139/m59-008

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The LD50ofPseudomonas aeruginosa(Schroeter) Migula was significantly decreased when the bacteria were injected into or fed to grasshoppers along with 1% granular mucin. In feeding experiments on 490 treated and 490 control insectsP.aeruginosain mucin was 6.4 times (5% fiducial limits of 3.4 and 11.9) as potent asP.aeruginosaalone. Mucin did not appear to speed the death of the grasshoppers. The action by which mucin promotes the infection was not determined.

ISSN:0008-4166    

DOI:10.1139/m59-009

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Bacterial isolates from the roots of wheat (rhizoplane) were more active in oxidizing glucose and alanine than cultures isolated from rhizosphere and non-rhizosphcre soils. In general, metabolic activity was greater with alanine than with glucose. Over one third of the cultures tested were capable of dissolving insoluble phosphorus in the form of CaHPO4but the roots did not appear to exert a selective effect on these forms. However, the phosphate-solubilizing organisms from the rhizoplane were also the most active in oxidizing glucose and alanine. Those from the rhizosphere soil were intermediate in this respect. By far the majority of these phosphate-dissolving bacteria were in the nutritional group requiring unknown substances in yeast and soil extracts for optimal growth. It was suggested that although these bacteria were not preferentially stimulated in the root zone, their large numbers and their greater metabolic activity may contribute significantly to the phosphate economy of the plant.

ISSN:0008-4166    

DOI:10.1139/m59-010

出版商:NRC Research Press    

年代:1959

数据来源: NRC