摘要:

The fatty acid composition of 42 isolates belonging to the major plant affinity groups ofRhizobiumhas been determined and found to vary reproducibly with culture age. Numerical taxonomic techniques applied to the 15 major fatty acid components of log-phase cultures of comparable physiological age showed that the rhizobia constitute a uniform group. However, two clusters comprising soybean–cowpea isolates and pea–bean isolates were evident. These observations, based on a simple analysis of only one group of chemical components, indicate relation ships among rhizobia which differ from the conventional plant-affinity groupings but which are consistent with other proposed relationships established using a variety of biochemical and physiological criteria.

ISSN:0008-4166    

DOI:10.1139/m79-011

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The cell walls ofFusarium sulphureumhave a microfibrillar component that is randomly arranged. X-ray-diffraction diagrams of the microfibrils are consistent with a high degree of crystallinity and show that they are chitin. The chitin microfibrils of the peripheral walls envelop the hyphal apex and extend across the septae. During the first 8 h in culture, the conversion of conidial cells to chlamydospores is evidenced by a swelling of the cells and the original microfibrils remain randomly arranged. Within 24 h new wall material is deposited as the cells expand and the wall thickens. The new microfibrils are indistinguishable from those of the original conidial cells.After 3 days in culture, the chlamydospores are fully developed and have the characteristic thick wall which is a continuous layer of randomly arranged microfibrils. Chlamydospores maintained in a conversion medium for 8 days have microfibrils identical with those in 3-day-old cultures; thus a further change in the microfibril orientation did not occur during that period.Alkaline hydrolysis of the walls removes most of the electron-dense staining constituents from the inner wall layer and leaves the outer wall layer intact. This treatment also reveals some of the wall microfibrils. An additional treatment of the walls with HAc/H2O2completely removes the wall components that react positively to heavy metal stains. The results are discussed in relation to the structure of other fungal cell walls.

ISSN:0008-4166    

DOI:10.1139/m79-012

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Seventeen temperature-sensitive mutants of bacteriophage SH-133 have been isolated following mutagenesis with UV-light, nitrosoguanidine, and ethyl methanesulfonate. The mutants were classified into 15 complementation groups according to their ability to complement each other at 32 °C, the nonpermissive temperature. Each mutant was studied with regard to the relationship between its ability to multiply in heterotrophically (H-) and autotrophically (A-) grownPseudomonas faciliscells. At 27 °C, the permissive temperature, the plaque-forming ability of the 17 mutants and wild-type phage was reduced 10-fold in A-grown cells. At 32 °C, mutants belonging to 10 groups exhibited identical levels of multiplicity-dependent leak under both modes of growth. However, the infection of A-grown cells by mutants belonging to the remaining five groups resulted in as much as 500-fold inhibition of multiplicity-dependent leak when contrasted with the infection of cells grown heterotrophically. These observations indicate that the expression of five SH-133 phage cistrons is defective when multiplication proceeds under autotrophic metabolism. Seven mutants were found to differ from the wild-type phage with regard to thermal stability at 56 °C which suggests that they possess altered structural proteins. Four of the seven thermosensitive mutants exhibited reduced levels of multiplicity-dependent leak in A-grown cells. The data suggest that the reduction in plaque-forming ability of SH-133 in A-grown cells is caused by a defect in the expression of specific phage structural components.

ISSN:0008-4166    

DOI:10.1139/m79-013

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Various enterobacteria exhibit several patterns of synthesis and excretion of polygalacturonic acidtrans-eliminase (PATE), one of the enzymes involved in degradation of pectic substances. In a strain ofErwinia chrysanthemi, PATE is an extracellular enzyme and is almost totally excreted. In strains ofYersinia enterocoliticaandYersinia pseudotuberculosis, PATE is a periplasmic and cytoplasmic enzyme. In a strain ofErwinia carotovora, PATE activity is extracellular, periplasmic, and cytoplasmic. In an "oxytocum" strain ofKlebsiella pneumoniae, PATE is entirely cytoplasmic; none is found in the periplasm and almost none in culture supernatants. Cells (but not supernatants, because PATE is not excreted) ofK.pneumoniaeshow much higher levels of PATE activity when grown on polygalacturonate than when grown on other carbon sources. A clinical strain ofY.enterocoliticasynthesizes high levels of PATE activity (almost all cell-bound) when grown in the presence of gluconate, glycerol, or polygalacturonate, and considerably less activity when grown on glucose. A clinical strain ofY.pseudotuberculosissynthesizes barely detectable quantities of cell-bound PATE regardless of the carbon source. The phytopathogenicErwiniastrains synthesize and excrete high levels of PATE activity when grown on polygalacturonate, galacturonate, gluconate, or glycerol. Growth on glucose represses PATE activity in theErwiniastrains; the extent of repression differs between the two strains. The different patterns of synthesis and excretion are discussed in the light of the possible catabolic and (or) cytolytic (plant tissue-macerating) functions and the related ecological significance of PATE in these enterobacteria.

ISSN:0008-4166    

DOI:10.1139/m79-014

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Under certain conditions, serum very low-density lipoproteins (VLDL) and high-density lipoproteins (HDL) can inhibit rubella hemagglutination. The level of this non-specific hemagglutination-inhibition (HI) activity increases as the incubation period between serum and antigen is increased. Treatment of serum with heparin–MnCl2does not precipitate HDL, and may not effect complete removal of all VLDL. This treatment method, therefore, should be considered a source of false-positive reactions, especially when extended serum–antigen incubation periods are used to enhance HI activity and to detect low levels of IgM.

ISSN:0008-4166    

DOI:10.1139/m79-015

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A quantitative soil debris isolation method (all debris from known weight of soil plated) and a garden beet seed saprophytic colonization method were compared over a 1-year period for assayingRhizoctonia solanipopulations. Four fields of different soil textures were selected. Within each field four areas of healthy and four areas of diseased (rhizoctonia root and crown rot) sugarbeets were sampled bimonthly from August 1976 until June 1977. The maximum numbers ofR.solanicolonies obtained by the debris method were 2 per gram of soil in areas of healthy beets, and 11 per gram of soil in areas of diseased sugarbeets. At such high inoculum densities the beet seed colonization method underestimatedR.solanipopulations, because the inoculum per unit of soil exceeded the numbers of beet seeds per unit of soil available for colonization. Modifications of the beet seed method did not significantly alter results of colonization assays. Ranked correlation comparisons of assay methods yieldedr = 0.81 for all data.

ISSN:0008-4166    

DOI:10.1139/m79-016

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A lysedTreponemabacterium containing cubic phage-like particles, approximately 40 nm in diameter, has been observed by negative staining electron microscopy.

ISSN:0008-4166    

DOI:10.1139/m79-017

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Cellsof Escherichia coliK-12 were stressed by heating at 48 °C or by acid treatment at pH 4.2 for periods up to 1 h. The addition of catalase to the selective medium increased the count of heat-stressed cells by 2.3-fold and acid-stressed cells by 4.8-fold. However, these values represented only a small percentage (3% for heat-stressed and 6% for acid-stressed cells respectively) of the population of injured but still viable cells. The addition of mannitol to the selective medium used to count acid-stressed cells did not increase the count. Whilst the presence of H2O2, in media may cause significant errors in the estimation ofE.coliin certain situations these errors are unlikely to be significant in physiological studies of populations of cells injured by stress.

ISSN:0008-4166    

DOI:10.1139/m79-018

出版商:NRC Research Press    

年代:1979

数据来源: NRC