摘要:

The physiological effects ofDL-ethionine and related methionine analogs upon cellular protein synthesis and methyl group transfer to aflatoxin B1inAspergillus parasiticuswere examined in growing and resting cell systems. The addition ofDL-ethionine (0.02 M) to growing mycelia inhibits cellular growth some 37% after 120 h of development. Addition of ethionine before 50 h prevents any aflatoxin synthesis; however, addition of ethionine after aflatoxin production begins has little effect upon continued synthesis. The enzymes responsible for aflatoxin production are made during the transitional phase of growth (50–70 h). During this period, ethionine administration blocks protein synthesis (measured by14C-methionine incorporation) 85% and prevents aflatoxin synthesis. Since exogenous ethionine (3.2 mM) inhibits aflatoxin B1synthesis about 50%, a competitive-type inhibition is indicated. Such inhibition is accompanied by the formation of a new aflatoxin B1derivative. The incorporation of14C-ethyl-ethionine into this derivative indicates a transethylation of the toxin ring system in the formation of ethoxy-aflatoxin B1. The addition ofDL-ethionine andS-ethylcysteine to proliferating cells yields some of the aflatoxin B1derivative.

ISSN:0008-4166    

DOI:10.1139/m71-094

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Evidence is presented for the isolation of DNA having a molecular weight of 31 ± 5 × 108fromBacillus subtilisstrain 23 Thy−cells. This accounts for the total DNA content of the genome. Single-strand and double-strand breaks induced by60Co gamma rays were measured by sucrose density centrifugation. The occurrence of repair of single-strand and possibly double-strand breaks at 0 °C is inferred from survival data and the effects of pre- or post-irradiation heating.

ISSN:0008-4166    

DOI:10.1139/m71-095

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A method is suggested for testing the biodegradability of insecticides using bacteria from a sewage lagoon. The proposal is based on results which showed that the biodegradable organophosphates Malathion, Parathion, and Diazinon were metabolized quickly by resting cell suspensions of lagoon bacteria while the persistent chlorinated hydrocarbons Heptachlor, Dieldrin, and DDT were metabolized poorly or not at all. Data also showed that oxygen was not an important regulator of catabolism for any of these insecticides. Heptachlor epoxide and DDD were the only metabolites identified. The advantages of the method are discussed.

ISSN:0008-4166    

DOI:10.1139/m71-096

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Micrococcus lysodeikticuswill grow in a defined medium, but only after an extended lag. The lag is lengthened by washing the inoculum, but this does not affect the final density of the culture. The lag for washed inocula is shortened by the addition of an iron-binding compound to the medium. The compounds effective in shortening the lag include both phenolic compounds and ferrichrome, a sideramine. Albomycin, a sideromycin, lengthens the lag for washed inocula but does not affect the final density of the culture. The iron-binding compounds which shorten the lag will antagonize the action of albomycin, as judged by the length of the lag, and will also stimulate the uptake of iron byM.lysodeikticus. Albomycin reduces the rate of uptake of iron. It is suggested that the initiation of growth inM.lysodeikticusis dependent upon the presence of an iron-binding compound, and that albomycin retards growth by decreasing the rate of uptake of iron.

ISSN:0008-4166    

DOI:10.1139/m71-097

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Anew tremorgenic mycotoxin, tremortin B, was found in the solvent extract ofPenicillium palitansmycelium. Tremortins A and B were purified by column chromatography on Florisil followed by Sephadex LH20, and recrystallized from several solvents. Tremortin B was determined to be C37H45NO5.The LD50of A is 1.05 mg and B, 5.84 mg/kg mouse. A third potential tremorgen, tremortin C, has also been isolated and purified, but so far the yield is insufficient to determine its characteristics.

ISSN:0008-4166    

DOI:10.1139/m71-098

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Vegetative nuclear division was studied inPenicillium notatumandP.chrysogenumusing light microscopy of stained preparations. The results obtained revealed mitoses in which duplicate sets of chromosomes were equitably divided into daughter genomes by successive division stages. From the resting stage consisting of a shell of granular chromatin, the dividing nucleus entered into a more densely staining stage containing chromosomes which appeared to be arranged in the formation of coiled cords. In the next stage of division the chromosomes became oriented into two parallel units and were then aligned in two's in a rectangular configuration. Division proceeded by movement of chromosomes to opposite poles. Mitosis included the development of a thin fiber which began as a deeply staining granule at one side of a spherical nucleolus. The granule divided into two components and then the thin fiber elongated between them.

ISSN:0008-4166    

DOI:10.1139/m71-099

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The diminutive pathogenic yeastTorulopsis glabratawas studied by light and electron microscopy, with special attention to the budding process. Polysaccharides were also extracted to determine glycogen in cytoplasmic particles. Elliptical single cells, with a mean volume of 13 μm3, possess ultrastructural features common in other yeasts, viz. nucleus with double membrane and pores, nucleolus, endoplasmic reticulum, mitochondria, vacuoles, lipid bodies, ribosomes, tripartite plasma membrane, and fibrillar wall with outer electron-dense layer. Numerous pocket-like invaginations of varying size and orientation are formed by the plasma membrane. Buds seem to be preceded by an elaboration of such invaginations and by tubular profiles of the endoplasmic reticulum present in the area of the emerging bud. As the bud protrudes, it appears bounded by a layer of newly synthesized wall material. In general, this process is similar to that in other yeasts (e.g.,Saccharomyces) but no vesicles were observed in the peripheral cytoplasm of the mother cell during the initial stages of budding. Various stages in the budding cycle are illustrated.

ISSN:0008-4166    

DOI:10.1139/m71-100

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A quantitative study was conducted of enzymes involved in the citric acid cycle and associated systems of the facultative autotrophThiobacillus novellusgrown on five different substrates. Irrespective of the growth substrate the organism possessed complete citric and glyoxylic acid cycles and the specific activity of α-ketoglutarate dehydrogenase was always quite low. Also, the activities of the enzymes of both cycles were usually lowest in extracts from autotrophic cells, and highest in extracts from acetate-grown cells. The three remaining extracts had activities that were between the two extremes with those from glucose-grown cells generally lower than those from pyruvate and succinate. Several exceptions should be noted among these generalizations. For example, the activity of aconitate hydratase and malic dehydrogenase was lowest in extracts from glucose-grown cells while that of isocitric dehydrogenase was lowest in extracts from pyruvate-grown cells. Transhydrogenase activity was virtually absent from extracts of pyruvate- and succinate-grown cells while NADH oxidase, which was identical in these two extracts, was also relatively low. Of interest is the large amount of cytochromecfound in high-speed supernatants. In extracts from autotrophic cells this was about 2.3% of the soluble protein and is suggestive of a significant role being played by the electron-transport system during growth of the organism.

ISSN:0008-4166    

DOI:10.1139/m71-101

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Hybridization experiments were conducted to detect nucleic acid homology among recognized species of lactobacilli. Tritiated complementary ribonucleic acid (RNA) was synthesized and reacted with homologous and heterologous deoxyribonucleic acid (DNA) preparations. The amount of radioactivity retained by nitrocellulose membrane filters indicated the degree of DNA–RNA interaction. The results were discussed in relation to a previous study in which lactobacilli were placed in three groups on the basis of the guanine plus cytosine (GC) content of the DNA. Group I; a 42% or greater reaction was observed whenLactobacillus helveticustritiated RNA was hybridized with DNA fromL.helveticus,L.bulgaricus,L.jugurti, andL. (jugurti)bulgaricus. The latter two strains appeared to be closely related and were easily distinguished fromL.helveticus. No appreciable cross reaction occurred withL.helveticustritiated RNA and DNA fromL.salivarius. Group II; no DNA–RNA hybrid formation was evident whenL.caseitritiated RNA was reacted with DNA fromL.plantarum,L.brevis, orL.buchneri; however, reactions of 50 to 100% were observed for nine strains ofL.casei. Group III;L.lactisappeared to be more closely related toL.leichmanniithan toL.delbrueckii. Also,L.fermentiandL.cellobiosusconstituted a distinct subgroup within group III. The results presented substantiate and further define the grouping based on GC content previously proposed. Further subdivision of each group was suggested. The possibility of a phylogenetic relationship between selected lactobacilli andBacillus coagulanswas discussed also.

ISSN:0008-4166    

DOI:10.1139/m71-102

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

APseudomonassp. capable of growing onp-fluorophenylacetic acid as sole carbon source has been isolated using the enrichment culture technique. All the organic fluorine is released into the culture medium as fluoride ion during growth. A number of fluorinated intermediates have been isolated from the culture medium when resting cells were incubated with the substrate. Using infrared, nuclear magnetic resonance, and mass spectroscopic techniques together with chemical degradative procedures, these have been identified asD(+)-monofluorosuccinic acid, trans-3-fluoro-3-hexenedioic acid, (−)-4-carboxymethyl-4-fluorobutanolide, 4-fluoro-2-hydroxyphenylacetic acid, and 4-fluoro-3-hydroxyphenylacetic acid.

ISSN:0008-4166    

DOI:10.1139/m71-103

出版商:NRC Research Press    

年代:1971

数据来源: NRC