摘要:

Tryptophan analogs known to act selectively on protein synthesis were used to study the effects of tryptophan depletion on the formation ofStaphylococcus aureus(Wood 46 strain) toxic material. The production of toxin during growth and its presence in culture supernatants were followed by determining alpha hemolytic activity in rabbit blood agar, lethality for mice, and immunodiffusion patterns with staphylococcal antitoxins. The following results were obtained when the bacteria were grown in the presence of 4- and 5-methyltryptophans and 7-azatryptophan: (1) growth inhibition from 20 to 50%; (2) loss of alpha hemolytic activity; (3) inability of culture supernatants to kill mice; (4) decrease in the number of antigens precipitating with staphylococcal antitoxin and absence of reaction with purified alpha antitoxin. No significant effects were observed with 5-fluorotryptophan; 6-methyltryptophan was totally inactive. All inhibitions were reversed byL-tryptophan, anthranilic acid, and indole, but only partially by chorismic acid, and not at all by shikimic acid. These observations are suggestive of a predominant role ofL-tryptophan in the synthesis of staphylococcal alpha toxin.

ISSN:0008-4166    

DOI:10.1139/m69-001

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In studying theEscherichia coliY10 (λ)-T4r+coliphage system, it was found that T4 excluded intracellular lambda, or lambda excluded T4, depending upon the experimental conditions. Either event was correlated with a significant increase in the specific activity of free intracellular DNase (deoxyribonuclease). During the first 20 minutes after induction of lambda by ultraviolet light, there was no increase in DNase specific activity and the cells responded to T4 as if they were non-induced. Adsorption of T4, or of T4 inactivated by ultraviolet light, led to a rapid increase in free intracellular DNase, the arrest of lambda replication, and infection of the cells by T4. From 20 to 60 minutes after induction there was a progressive increase in free intracellular DNase, accompanied by an increasing ability of the cells to resist T4 infection.The RNase (ribonuclease) treatment of all cellular extracts, whether from normal cells or from cells infected with T4 or lambda, led to a considerable enhancement of DNase activity. This treatment showed that an increase in total DNase activity occurred by 40 to 60 minutes after lambda induction, but failed to reveal any such increase in total DNase activity resulting from successful T4 superinfection.

ISSN:0008-4166    

DOI:10.1139/m69-002

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Heating of partially purifiedStaphylococcus aureusMF-31 ribosomes at temperatures ranging from 37 C to 55 C in buffer containing magnesium, phosphate, or ethylenediaminetetraacetic acid (EDTA) caused the degradation of the ribosomes. The degradation in phosphate was similar to that in EDTA but was greater than that in magnesium. Polynucleotide phosphorylase and ribonuclease were implicated as the enzymes involved. Degradation was stimulated by heat at temperatures comparable to those at which sublethal injury and ribosome loss occurred in the intact resting cells.

ISSN:0008-4166    

DOI:10.1139/m69-003

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Biotin-requiring mutants have been isolated fromEscherichia coliK-12 and classified into four nutritional groups on the basis of their responses to various biotin vitamers, the ability to feed other mutant strains, and the nature of vitamers excreted into the growth medium. The growth response of the mutant strains to various biotin vitamers was in a linear sequence starting from 7-keto-8-aminopelargonic acid to 7,8-diaminopelargonic acid, to desthiobiotin, and to biotin. From the results of the cross-feeding experiments the excretion of three types of vitamers was indicated and two of the vitamers were identified as desthiobiotin and 7-keto-8-aminopelargonic acid. The third vitamer could not be detected by bio-autographic technique. From these results a biosynthetic pathway of biotin inE.colihas been proposed.

ISSN:0008-4166    

DOI:10.1139/m69-004

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A strain ofPseudomonaswas grown with phenylacetic acid as the carbon source in batch, continuous, and phased cultures. The cellular activities of the inducible enzymes involved in the sequential degradation of phenylacetic acid [phenylacetic acid →p-hydroxyphenylacetic acid →3,4-dihydroxyphenylacetic acid →δ-carboxymethyl-α-hydroxymuconic semialdehyde] varied with the above methods of culture, and illustrate microbial reaction to environment (10). The effect of substrate concentration on the activity of the enzymes in the metabolic breakdown of phenylacetic acid is discussed.The changes observed in the cells show some of the disadvantages inherent in batch cultivation methods for the production of certain enzymes and some of the relative advantages in chemostat and continuous phased cultures for obtaining higher yields.

ISSN:0008-4166    

DOI:10.1139/m69-005

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The culture of two human strains of mycobacteria (H37Rv and H37Ra) on Sauton medium differs from that of a bovine strain (BCG) in the later phases of growth of the three strains. The yield of soluble non-dialyzable mycobacterial constituents extracted from the bacillary bodies is more elevated in the lag and the exponential phases of growth than in the later phases of growth. The appearance of mycobacterial constituents in culture filtrates of H37Rv and H37Ra occurs in two successive steps. The content of tuberculin in culture filtrates of strain BCG is very low.

ISSN:0008-4166    

DOI:10.1139/m69-006

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The free-energy changes involved in the oxidation of ferrous iron by the ferrobacilli have been recalculated. Microcalorimetric measurements of the heat output of the oxidation have shown that the recalculated free-energy changes are in harmony with these measurements in that the measured heat output differs from the calculated free energy by an amount approximating to the theoretical entropy change involved.

ISSN:0008-4166    

DOI:10.1139/m69-007

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In October, 1963, during a time of abundance of microtine rodents,Pasteurella tularensiswas isolated from a northern vole,Microtus oeconomusPallas, at the Ugashik Lakes on the upper Alaska Peninsula. The morphological, cultural, and serological characteristics of this isolate are described, and comparative virulence in experimentally inoculated animals, including series of indigenous rodents, is discussed. The isolate was less virulent for rabbits and guinea pigs than was that which has been isolated previously from ticks,Haemaphysalis leporispalustris(Packard), in Alaska, and was also less virulent for these animals than was strain SCHU S4. The isolate from the vole seemed to resemble most closely the Eurasian strain ofP.tularensis, as might be expected on zoogeographical grounds. A distinguishing feature of the isolate was its ability to grow readily on blood agar in the absence of cystine. The relatively high rate of subclinical tularemia in man in northern and western Alaska, as indicated by the results of serological tests, may be attributable to this organism. Water-borne bacteria may be the source of infection in man.

ISSN:0008-4166    

DOI:10.1139/m69-008

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The stimulatory effect of acetyl-CoA and the inhibitory effect byL-aspartate and some intermediates of the tricarboxylic acid cycle in the assimilation of CO2by crude extracts of group D streptococci suggest that the pyruvate carboxylase ofStreptococcus faeciumand the phosphoenolpyruvate carboxylase ofS.bovisare allosteric enzymes. This implies that these enzymes are sites for the control of the amount of aspartate and of the tricarboxylic acid cycle intermediates synthesized.

ISSN:0008-4166    

DOI:10.1139/m69-009

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Cell-free extracts of group D streptococci incorporated14CO2into aspartate. Pyruvate was the acceptor of CO2forStreptococcus faecium; phosphoenolpyruvate was the CO2acceptor forS.bovis; and both substrates were CO2acceptors forS.faecalis. The enzymes, by which the CO2fixation was effected, appear to be pyruvate carboxylase forS.faecium, phosphoenolpyruvate (PEP) carboxykinase and PEP carboxylase forS.bovis, and pyruvate carboxylase and PEP carboxykinase forS.faecalis.

ISSN:0008-4166    

DOI:10.1139/m69-010

出版商:NRC Research Press    

年代:1969

数据来源: NRC