摘要:

Models for the inactivation of bacterial spores for the case of continuously decreasing death rate are reviewed and extended to show that it is not possible to distinguish between one particular model based upon the innate heterogeneity of the population and that based upon the acquisition of heat resistance during the heating process. Two innate heterogeneity models have been fitted to published data.

ISSN:0008-4166    

DOI:10.1139/m77-223

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The cell walls of the fungusDrechslera sorokinianaand an albino mutant have been studied to determine if disappearance of pigment also involves an important modification of the chemical structure. The albino mutant has lost, besides the pigment, pentose, xylose, and part of galactose and mannose. The protein contents as well as those of hexosamine and chitin are not modified. After treatments of the walls with 2 MNaOH – 0.5 MH2SO4and with ethylenediamine identical compounds are isolated from the two walls; however, cell walls of the mutant are more easily and more extensively degraded than those of the wild type. This difference in resistance is not only due to the presence of pigment but also to a different architectural structure of the two cell walls.

ISSN:0008-4166    

DOI:10.1139/m77-224

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Light- and electron-microscopic examination showed that bacteria became associated with the hyphae and asexual reproductive structures ofP.cinnamomiin soil. In suppressive soils this association appears to be correlated with hyphal lysis, inhibition of zoospore production, and sporangial breakdown. One notable feature of the microbial association betweenP.cinnamomiand soil bacteria is the formation of extensive slime material. Many of the bacteria isolated from the fungal hyphosphere display antagonism to the growth ofP.cinnamomiin vitro. The bacteria are morphologically varied and includePseudomonas,Bacillus, andStreptomycesspp. These observations suggest that the appropriate manipulation of the antagonistic bacteria may provide a means of biological control ofP.cinnamomi.

ISSN:0008-4166    

DOI:10.1139/m77-225

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The mouse model of intraperitoneal meningococcal sepsis was used to evaluate the antiendotoxic activity of polymyxin B sulfate independent of its antibiotic effects. Administered either before or after the infective challenge therapeutic doses of polymyxin B sulfate produced small but significant increases in survival over unprotected animals. These results also suggest that endotoxin contributes to the outcome in this variety of Gram-negative infection.

ISSN:0008-4166    

DOI:10.1139/m77-226

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The inoculation of the EuropeanAlnus glutinosa(L.) Gaertn. host plant by a crushed-nodule inoculum, prepared with the North-AmericanAlnus crispavar.mollisFern, root nodule, was successful. Fluorescein- and ferritin-labelled antibodies, specific against theA.crispavar.mollisroot nodule endophyte (Lalondeet al. 1975), demonstrated the identity of this endophyte in the resulting nodules. The nodulation process of this abnormal host–endophyte system was studied by light and electron microscopy. An excretion of host blebs containing electron-dense polysaccharide material, resulting in the formation of exo-encapsulation threads containing presumptive endophytic bacterial cells, was associated with deformed root hairs. Originating from an exoen-capsulation thread, the endophyte penetrates the root hair cell and then migrates as a hypha toward the cortical cells of the root. Its migration in the cortical cells of the primary nodule results in the induction of a lateral root which develops as the true nodule. The ultrastructure of theA.crispavar.mollisendophyte developing in the primary and true nodule of the abnormalA.glutinosahost was similar to the one induced inside its normalA.crispavar.mollishost. The actinomycetal intruder was a branched and septate hypha able to produce septate vesicles. The endophyte was always encapsulated in an electron-dense polysaccharide material surrounded by a host plasma membrane envelope. However, in this abnormal host–endophyte system, the number of primary nodules formed per root system was drastically reduced, and their appearance was delayed by 1 to 2 weeks. The delayed nodules were effective in fixing nitrogen and able to support satisfactory plant growth in a nitrogen-free medium.

ISSN:0008-4166    

DOI:10.1139/m77-227

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Nitrogenase inAzotobacter chroococcumwhole cells was inhibited by enzymically generated superoxide anion (O2−), hydrogen peroxide, and ethyl hydrogen peroxide. The degree of inhibition produced by O2−was related to the quantity of oxygen supplied to the organisms in continuous cultures. O2−also inhibited oxygen uptake by whole cells. These O2−-mediated inhibitions were prevented by bovine superoxide dismutase. The quantities of superoxide dismutase (SOD), and catalase associated with cells grown under varying oxygen concentrations were determined. The role of hydrogen peroxide, and of the hydroxyl radical (∙OH) in nitrogenase inhibition was examined. The response ofAzotobacter chroococcumto oxygen was evaluated with respect to the observed effects of O2−on the organism, and some explanation is given to account for nitrogenase sensitivity to oxyge

ISSN:0008-4166    

DOI:10.1139/m77-228

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

When tumorigenic strains ofAgrobacterium tumefacienswere subcultured at temperatures between 31.5 and 37 °C or in broth containing ethidium bromide, they lost their capacity to induce tumors in tomato plants. The sensitivities of curing virulence (tumorigenicity) depended on the density of the population of cells, fewer cells (100/ml) being more sensitive to curing than higher densities (106/ml). The loss of virulence need not require the total loss of the virulence-specifying plasmid, but may result from a loss of a small segment of that plasmid. Virulent strains made avirulent by temperature or ethidium bromide treatment still harbor a large plasmid of 70–80 megadaltons size compared with the 100-to 120-megadalton plasmid in the untreated strains.

ISSN:0008-4166    

DOI:10.1139/m77-229

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Studies on the effects of inhibitors of the nitrate-reducing activity ofVeillonella alcalescensextracts suggest the participation of a naphthoquinone, ab-type cytochrome, and non-heme iron in electron transport to nitrate. A nitrate-reductase-deficient mutant displayed a longer doubling time and a decreased molar growth yield on nitrate media. This mutant was phenotypically restored by the addition of molybdate to the growth medium, giving evidence for the functioning of molybdenum in the nitrate-reductase enzyme ofV.alcalescens.

ISSN:0008-4166    

DOI:10.1139/m77-230

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A new species ofArthrobacteris described for which the nameA.sialophilusis proposed. The organism was obtained by elective culture from soil using Collocalia mucoid, and can readily be induced in replacement minimal media with appropriate substrates, to form the enzyme neuraminidase. It undergoes sphere–rod–sphere morphogenesis, is gram-variable, non-motile, aerobic, catalase-positive, oxidase-negative, fails to release acid or gas from saccharides, has a GC content of 56.0 mol % and can grow at temperatures up to 45 °C. The peptidoglycan composition of its spherical form contains neither diaminopimelic acid nor arabinose as components, but does manifest the presence of glycine. Its generation time at 30 °C on tryptone – yeast extract medium is 1.6 h. Accessory growth factors do not appear to be required. The organism, though colorless in the dark, provides a bright yellow water-insoluble pigment after exposure to light. The foregoing combination of properties distinguishes this isolate from other well-describedArthrobacterspp.

ISSN:0008-4166    

DOI:10.1139/m77-231

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Pasteuria ramosa, a bacterial parasite of the cladoceransDaphnia pulexandD.magna, was described by Metchnikoff in 1888. Because the organism could not be cultured, it was subsequently lost. However, the original illustrations and descriptions of the life cycle ofP.ramosaare similar to a bacterial spore parasite of nematodes (BSPN) that was recently described inMeloidogyne. As a result of these similarities, a search forP.ramosawas initiated. An organism resemblingP.ramosawas found infectingMoina rectirostris, a member of the Daphnidae and a new host for the bacterium. Photomicrographs and scanning electron micrographs of the parasite indicated that the morphology of this organism was similar to the descriptions and illustrations presented by Metchnikoff. Morphological features of this newly described parasite also indicate that the bacterium is similar to the BSPN.

ISSN:0008-4166    

DOI:10.1139/m77-232

出版商:NRC Research Press    

年代:1977

数据来源: NRC