摘要:

Tests comparing the pour and surface plate methods for determination of bacterial numbers in ice, in water, and on processed birds in poultry plants showed that counts for the latter technique were about 70% and 80% higher than those for the former at incubation temperatures of 0 °C and 22–25 °C, respectively. Recovery studies with pure cultures indicated that the difference was related to both type and strain of bacteria. The pseudomonads as a group did not contribute to the difference, whereas some but not all of the achromobacter tested contributed markedly.

ISSN:0008-4166    

DOI:10.1139/m67-187

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Carbon dioxide fixation was studied in intact cells and cell-free extracts ofFerrobacillus ferrooxidans. The major pathways of fixation were found to be the carboxydismutase system and the phosphoenolpyruvate (PEP) carboxylase system. PEP carboxylase activity was shown to be under metabolic regulation, similar to the regulation established in heterotrophic microorganisms.Acetyl-CoA stimulated PEP carboxylase activity, while aspartate was inhibitory. TheF.ferrooxidansenzyme appeared to have a neutral or acidic pH optimum, in contrast to the same enzyme isolated from heterotrophs.

ISSN:0008-4166    

DOI:10.1139/m67-188

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Repeated assays of standard preparations of interferon carried out for over a year using primary cultures of chick-embryo cells and Sindbis virus in an assay system showed that cell cultures varied in their sensitivity to interferon. This altered sensitivity was not due to a change in the challenge virus nor to the time of exposure of cells to interferon. An analysis of the data showed that the slope of the dose–response curves remained constant although they could be displaced, indicating changes in sensitivity. Information was also obtained demonstrating that sensitivity of cells to interferon could vary within a single assay.

ISSN:0008-4166    

DOI:10.1139/m67-189

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Salt-dependent, salt-resistant, and salt-sensitive bacteria were found at depths of 0–50 cm in a hydrohalomorphic soil near the shore of the Red Sea. Highest counts were obtained on soil-extract agar supplemented with 5% sodium chloride, 0.02% yeast extract, and 0.04% Casitone. Most of the bacteria, upon initial isolation, failed to grow on counting media containing 5% or 10% sodium chloride unless yeast extract and Casitone were present. However, all isolates, randomly selected from the counting medium containing 10% sodium chloride and supplemented with yeast extract and Casitone, did not need these supplements when transferred onto a new medium of the same salt concentration.Bacterial counts were significantly affected by the salt concentration of both the diluting solution and the growth media. It was concluded that the addition of yeast extract and Casitone to the growth media resulted in a partial recovery and protection of the cells from damage occurring during the initial dilution and plating procedure.

ISSN:0008-4166    

DOI:10.1139/m67-190

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The induction and the growth of viral SV 40 tumors in hamsters can be influenced by treating the animals with the oncogenic virus itself. The virus can be used to vaccinate against the transplanted tumor cells; it can also be used as a treatment to prevent the development of the tumor after its induction in the newborn by the virus or in the adult by the implantation of tumor cells.The present study reports that the administration of SV 40 virus to adult hamsters immediately following the excision of their transplanted SV 40 tumor brings a reduction in the frequency of recurrences appearing after the operation. It was also observed that among the animals that did not present recurrences after 7 to 10 months, those that were treated with the virus at the time of the surgical intervention, were still more resistant to the reimplantation of homologous cancer cells.These observations are interpreted as another indication that the evolution of a tumor can be modified in a favorable way by immunological means, in this instance, by a treatment with the oncogenic virus itself.

ISSN:0008-4166    

DOI:10.1139/m67-191

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The effect of O2and CO2on proteinase biosynthesis by nonproliferating cells ofStreptococcus faecalisvar.liquefaciensin chemically defined media were studied. In the absence of CO2, O2(1% in N2) stimulated proteinase formation by promoting earlier synthesis and by increasing the rate of enzyme biosynthesis. Carbon dioxide under anaerobic conditions only enhanced the rate of proteinase synthesis. The stimulatory effect of the two gases was not additive. Glucose supported a greater yield of proteinase than galactose under all conditions of O2and CO2availability. Galactose was stimulatory in the presence of glucose only under aerobic conditions (1% O2in N2) when atmospheric CO2was removed. Oxygen at the 20% level inhibited proteinase formation by increasing the rate of arginine disappearance from the medium.

ISSN:0008-4166    

DOI:10.1139/m67-192

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Sporidesmin, gliotoxin, and chetomin increase the lag phase of growth ofBacillus subtilis. By daily subculture of the organism in media that contained one of the antibiotics in sufficient concentration to increase the lag phase of growth by 300%, organisms were obtained whose lag phase of growth was the same as that of the parent strain (HLX 373). Repetition of this process has made it possible to obtain cultures which have a lag phase of growth of 300 ± 20 min in the presence of chetomin (0.15 μg/ml), gliotoxin (3.0 μg/ml), or sporidesmin (30 μg/ml). The culture which could grow in the presence of gliotoxin lost this ability on subcultivation in the absence of the antibiotic. Sufficient cross resistance was shown to indicate the possibility that these three antibiotics had a similar mode of action.

ISSN:0008-4166    

DOI:10.1139/m67-193

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Addition of a small portion of autoclaved soil to normal soil provided some degree of protection against die-out forEscherichia colicells also introduced into this soil. This protection was associated with organic carbon (glucose) availability, but not with nitrogen (ammonium nitrate) availability. AnE.colipopulation was stabilized, at least temporarily, in soil by glucose feeding, and the protective effect of glucose was temperature dependent. Indigenous micro-organisms also multiplied in the glucose-amended soil, and, therefore, colonizing space and microbial production of compounds toxic toE.coliwere not considered to be major controlling factors inE.colidie-out in soil.E.colicells recovered after residence in this soil demonstrated an initial decreased growth rate which was less pronounced in cells recovered from glucose-amended soil and which disappeared for both cell types on subculture. It was concluded that a major factor inE.colidie-out from natural soil is its inability to step down its metabolic rate to meet the low availability of usable organic carbon in soil.

ISSN:0008-4166    

DOI:10.1139/m67-194

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The membranes fromM.lysodeikticuscan readily be disaggregated into a very small subunit form with sodium lauryl sulfate. Reaggregation of these subunits into membranous sheets occurs during dialysis in a menstruum of relatively low ionic strength, in the presence of a divalent cation at near neutral pH. Reducing conditions and a monovalent salt need not be present during dialysis. Effect of several compounds on membranes and subunit reaggregation was studied. Reaggregated membrane sheets are very similar chemically and morphologically to whole membranes; however, a difference was noted. The major bonding mode in membranes appears to involve hydrophobic groups.

ISSN:0008-4166    

DOI:10.1139/m67-195

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

An attempt has been made to determine the nature of an antiviral substance derived fromPenicillium cyaneo-fulvum. Although the material was available only in semipurified state, horizontal electrophoresis showed just two components present, one with a positive charge and the other with a negative one. Both stained with mucicarmine and Amido black. After hydrolysis of the preparation, 13 amino acids were identified by two-dimensional chromatography. Preliminary studies indicate that the semipurified material contains 21–25% reducing sugar. The effect of a variety of enzymes on the activity of the preparation has been studied. The results indicate that the antiviral substance may be an amino acid – carbohydrate complex.

ISSN:0008-4166    

DOI:10.1139/m67-196

出版商:NRC Research Press    

年代:1967

数据来源: NRC