摘要:

Cans of ground cooked beef, inoculated with 106or 108spores per can ofClostridium botulinum33A, were irradiated with60Co gamma rays at a series of 14 temperatures ranging from −196 to 95C. The higher inoculum level required higher sterilizing doses. TheDvalues, computed on the basis of recoverableC.botulinum, were independent of the inoculum level, and showed that spore resistance progressively decreased with increasing temperature. A statistical analysis of these data disclosed that the change inDvalues from −196 to 65C followed equally well a quadratic, exponential, or linear best-fit plot; above 65C radiation death was much more rapid. An equation was derived from the linear plot to predictDvalues for any desired temperature between −196 and 65C. Calculations ofEaandQ10values, based on the linear curve, indicated a very small thermodynamic effect on radiation kill. An Arrhenius analysis of the temperature effect suggested that there was no simple physicochemical mechanism occurring in the inoculated beef pack which might explain the change in spore kill as a function of temperature. Theoretical commercial radiation processes for beef, based on the 12Dconcept and strain 33A spores, are presented for several easily controlled irradiation temperatures.

ISSN:0008-4166    

DOI:10.1139/m71-024

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The rickettsial agentCoxiella burnetiwas studied in cultured mouse L cells by use of the electron microscope. Rickettsiae gain entry to the host cell in an apparently passive manner through phagocytic activity by L cells. The L cells show a lysosomal response to the presence of rickettsiae, as determined by cytochemical tests for acid phosphatase and 5′-nucleotidase. Further, examination ofC.burnetiwithin lysosomes suggests that rickettsiae can be degraded by the host cell. Autoradiographic analyses using tritiated thymidine show that rickettsial DNA is largely restricted to the dense nucleoid region, and when such labeled rickettsiae are used to inoculate L cells, most of the label becomes localized in the host cell nucleus. The above information is discussed in terms of dynamic interactions betweenC.burnetiand infected L cells.

ISSN:0008-4166    

DOI:10.1139/m71-025

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The hemagglutinating activity of the canine adenoviruses was found to be more than 80% associated with both the intact and incomplete ('empty') virus particles, the remaining complete hemagglutinating activity being associated with a naturally occurring soluble penton dimer structure. Trypsin treatment of the hemagglutinin – red blood cell complex and receptor-competition experiments, using purified fiber component to block the receptor sites on the red blood cells, indicate that there are different receptors for infectious canine laryngotracheitis (ICL) virus and infectious canine hepatitis (ICH) virus.The ICL adenovirus was found to hemagglutinate human and rat erythrocytes but not those of a number of other animal species. Using human group 'O' erythrocytes the ICL virus associated hemagglutinating activity was found to occur over a wide range in temperature and pH, and certain purification procedures, such as fluorocarbon treatment and sonic oscillation, were found to inactivate the hemagglutinin rapidly.

ISSN:0008-4166    

DOI:10.1139/m71-026

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A bacteriophage infective for the obligate psychrophile,Micrococcus cryophilus, was isolated from sewage. The host range is limited to this species. Phage and host DNA are similar in G–C content. The bacteriophage has an average burst size of 290 at 20 °C and 50 at 3.5 °C. The phage is thermosensitive, being 99.9% inactivated in 5 min at 45 °C. This is the first report of the isolation of bacteriophage infective for gram-positive psychrophiles.

ISSN:0008-4166    

DOI:10.1139/m71-027

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Purified Sindbis virus is split into two components upon treatment with ether. These are (a) a hemagglutinin which sediments at 55 S and is non-infectious. This fraction was shown to be devoid of phospholipid and to contain the envelope structural protein of the virion; (b) a fraction sedimenting at 135 S, which is devoid of RNA, but contains viral nucleocapsid structural protein. This fraction may represent the RNA-less nucleocapsid of the virion.

ISSN:0008-4166    

DOI:10.1139/m71-028

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

By using the acridine orange staining technique a green fluorescence, characteristic of double-stranded nucleic acid, can be observed with purified preparations of mycobacteriophage C2 and its extracted nucleic acid. DNAse-treated samples do not show this fluorescence, which leads to the conclusion that this fluorescence is associated with phage DNA. Examination of preparations of phage grown in the presence of acridine orange supported these results.

ISSN:0008-4166    

DOI:10.1139/m71-029

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Iron uptake inBacillus subtilisis mediated by a system which is specific for, and repressed by, iron and which requires an energy supply and is dependent upon the integrity of the cell membrane.

ISSN:0008-4166    

DOI:10.1139/m71-030

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The thermal inactivation of stable and unstable (persistent lethal sectoring) lines of yeast was investigated at various temperatures. The temperature dependence of mortality rate was adequately described by the first-order chemical reaction formula. A semilog plot of temperature vs. life time of the stable line appeared as a straight line. On the other hand, that of the unstable line had two components: one had the same activation energy as the stable line and the other one had a different lower value. This new component may have originated in a mutated protein and caused the instability.

ISSN:0008-4166    

DOI:10.1139/m71-031

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Valinomycin, monactin, and nonactin were found to affect the motility ofPseudomonas fluorescens. Cells "loaded" with42K rapidly exchanged it with K+when exposed to the above compounds, and uptake of such unlabeled K+resulted in a net increase in total potassium content. Hydrogen ions also moved rapidly into the antibiotic-treated organisms, and both potassium and hydrogen ion permeability were used as measures of membrane integrity. Alteration of membranes by these antibiotics suggests a possible relationship between this and diminution of flagellar activity. Membrane-active antibiotics may be useful agents for studying membrane-mediated transformations of chemical into mechanical energy using motile bacteria as model systems.

ISSN:0008-4166    

DOI:10.1139/m71-032

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Drugs known to block impulse transmittance, or that depolarize membranes, severely affected motility inRhodospirillum rubrumandThiospirillum jenense. Procain, serotonine creatinine sulfate, neostigmine methyl sulfate, eserine sulfate, atropin sulfate, parathion, acetylcholine chloride, and mersalyl acid, all were active in this respect. It is suggested that a system involving electrical potential differences in bacterial membranes may possibly play a role in bacterial flagellar motility.

ISSN:0008-4166    

DOI:10.1139/m71-033

出版商:NRC Research Press    

年代:1971

数据来源: NRC