摘要:

In a medium containing pyridoxal, a strain ofS.lactisgrew when arginine, histidine, isoleucine, leucine, phenylalanine, proline, valine, and either methionine, homocysteine, or cystathionine were supplied. Serine did not stimulate growth with homocysteine. In a medium with a mixture of 18 amino acids, pyridoxal was not required for growth; methionine was essential but homocysteine or cystathionine failed to replace methionine unless pyridoxal was present. These results indicated that conversion of homocysteine to methionine by this organism may involve vitamin B6but not serine.

ISSN:0008-4166    

DOI:10.1139/m57-084

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

A study has been made of the specificity of the requirement of some marine bacteria for halides, magnesium, calcium, and iron and of their quantitative requirements for these ions in the presence and absence of related ions.All of the organisms investigated either required or responded to the addition of Cl−to the medium. Br−could replace Cl−but somewhat less readily, while I−was toxic. For organism B-16, which required the addition of Mg++but not Ca++to the medium, the amount of Mg++required for maximum growth varied with the level of Ca++present. At low levels, a marked sparing action of Ca++was evident, while at higher concentrations of Ca++some antagonism between the ions was detected. Sr++also spared the Mg++requirement of this organism. For B-9, which required both Mg++and Ca++, Mg++could be shown to spare the need for Ca++.An absolute requirement of one organism for Fe++was demonstrated. Ni++and Co++showed no sparing action and proved to be toxic at a level at which Fe++produced an optimum growth response.

ISSN:0008-4166    

DOI:10.1139/m57-085

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Evidence is given for the existence of a hemicellulase and a cellulase in uredospores ofPuccinia graminisvar.tritici. Pectinase is also present and is shown to be an adaptive enzyme. The pH and temperature optima of these three cell-wall-splilting enzymes have been determined by means of viscosimetric measurements. Preliminary investigations using the mannogalactan ofCeratonia siliquaL. as a substrate for hemicellulase and carboxymethylcellulose as a substrate for cellulase indicate that degradation with the enzymes of ungerminated rust involves attack on internal linkages of the substrate molecule, giving a rapid decrease in viscosity with slow production of free reducing groups. The influence of heavy metal salts, reducing agents, and iodoacetic acid was examined.

ISSN:0008-4166    

DOI:10.1139/m57-086

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

The behavior of the nuclei in resting and germinating spores and in growing hyphae ofMucor hiemalishas been followed during life with phase contrast microscopy. The nuclei consist of a dense central body, the nucleolus, surrounded by a shell of variable shape composed of optically uniform material of low density. The nuclei have been seen to divide by constriction. One half of the nucleolus and one half-shell of the low density material pass to each daughter nucleus.All phases of nuclear division have been recognized in fixed and stained preparations. The nucleolus is readily stained by iron hematoxylin or gentian violet but is Feulgen-negative. The shell of low density has no marked affinity for hematoxylin and other basic or acid stains although it consists largely of granules and filaments which are Feulgen-positive. In these elements the chromosomes of the nuclei must somehow be contained but the size, shape, and behavior of individual chromosomes cannot yet be described. Division of the mass of chromatinic elements is direct and involves neither spindle nor metaphase plate. It is tentatively proposed that the chromosomes in the resting nucleus are already divided and segregated to opposite sides and that the constriction of the nucleus is merely the consummation of a kind of endomitosis initiated during the terminal stages of the previous division. Supporting observations have been made onMucor fragilis, several other Mucorales, and two species ofSaprolegnia. Uncertainties and controversies of the past can be explained in the light of the new findings.

ISSN:0008-4166    

DOI:10.1139/m57-087

出版商:NRC Research Press    

年代:1957

数据来源: NRC

摘要:

Nuclei of the sporangiospores of seven strains and the growing hyphae of five strains ofPhycomyces blakesleeanushave been examined in fixed and stained preparations. One strain was found to have unusually large nuclei and has been studied in detail. The nuclei in the sporangiospores consist of Feulgenpositive granules and short filaments in a diffuse matrix. In the ordinary strains the nuclei occur in a narrow range of sizes with their largest diameters around 2 microns. In the spores of the unusual culture the nuclei are of several sizes and many have diameters around 4 and 5 microns.Similar differences are found between the nuclei in growing mycelia. The nuclei in hyphae resemble those ofMucor hiemalis. They consist of a shell of tightly packed granules and filaments of chromatin curving around a relatively large nucleolus. The nuclei divide by elongation followed by constriction. The nucleolus divides at the same time and in the same way and half of it passes to each sister nucleus. The possibility is discussed that the strain with the large nuclei may have had its origin in a spore formed by a germinating zygote and containing both haploid and diploid nuclei. The nuclei of the unusual culture, first examined 3 years ago, have preserved their large size through many cycles of vegetative propagation.

ISSN:0008-4166    

DOI:10.1139/m57-088

出版商:NRC Research Press    

年代:1957

数据来源: NRC