摘要:

The synthesis of proteins in response to a cold shock in the psychrotrophic yeastTrichosporon pullulanswas examined. Two-dimensional electrophoretic analysis of a 21 to 5 °C cold shock revealed the induction of 26 cold-shock proteins (csps) at the maximum induction time of 12 h. The induction of only 10 csps after a 24 to 5 °C cold shock suggested that the growth of cells above their optimum growth temperature reduced their ability to induce csps. Comparison of the csp profile obtained after a 15 to a 5 °C cold shock with the profile for the 21 to 5 °C cold shock suggested that the range of the cold shock influences which proteins are induced.Key words: cold-shock proteins, psychrotrophic yeast.

ISSN:0008-4166    

DOI:10.1139/m90-091

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Ammonia-induced cell envelope injury was examined in pure cultures ofEscherichia coliandEnterobacter aerogenes. Cell injury, as determined by the ratio of colony-forming units on m-T7 agar to colony-forming units on m-Endo agar, increased with exposure to increasing concentrations of ammonia. Cell envelopes appeared to be the site of injury as indicated by increasing susceptibility to lysozyme with increasing ammonia concentration. Cells exposed to ammonia also exhibited more cellular leakage than control cells. Leakage from cells exposed to ammonia included proteins, and all leaked substances increased in concentration as ammonia concentrations increased. The concentration of 2-keto-3-deoxyoctonate (KDO) in the outer membrane ofE.coliincreased with ammonia exposure, while KDO concentration in the outer membrane ofE.aerogenesdecreased. The results suggest that exposure ofE.colicells to high concentrations of ammonia disrupts the outer membrane and lipopolysaccharide-associated proteins, whileE.aerogenescells are affected through the disruption of bonds between KDO and the outer membrane.Key words: injury, coliform, ammonia, cell envelope.

ISSN:0008-4166    

DOI:10.1139/m90-092

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The fungal parasite of eggs of cyst nematodes,Verticillium suchlasporium, produced extracellular proteases when grown in semiliquid culture with gelatin as the only source of nitrogen and carbon. The proteolytic activity of culture filtrates was maximum 12–14 days after inoculation. Gel filtration chromatography in Sephadex G-100 resolved two peaks of proteolytic activity. The peak accounting for most of the activity was further purified by ion-exchange chromatography in SP-Sephadex C-25 as a single peak. This protease had a molecular mass of 32 kDa calculated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. The enzyme was an endopeptidase that degraded fibrinogen in zymograms and had an optimum pH of 8.5 using fluorescein isothiocyanate – casein as the substrate. It was inhibited by phenylmethylsulfonyl fluoride, indicating that it was a serine protease. The purified protease was able to degrade certain cyst nematode proteins suggesting the involvement and specificity of the 32-kDa protease during nematode egg penetration byVerticillium suchlasporium.Key words: nematophagous fungi,Verticillium suchlasporium, extracellular enzymes, serine proteases.

ISSN:0008-4166    

DOI:10.1139/m90-093

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Polymorphisms were readily detected in polydnavirus DNA extracted from several different species belonging to two different families of parasitic hymenoptera. Heterogeneity was observed as differences in electrophoretic profiles of genome segments, differences in the number of cross-hybridizing genome segments, and restriction fragment length polymorphisms; polymorphism was also detected at the level of an individual genome segment. Some implications drawn from these observations are discussed.Key words: polydnavirus, multipartite genomes, DNA polymorphisms.

ISSN:0008-4166    

DOI:10.1139/m90-094

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Pure culture suspensions of two strains of exponential and stationary phaseEscherichia coliexhibited significant reductions in catalase activity following exposure to acid mine water (AMW). The exogenous addition of catalase (500–2000 U) or sodium pyruvate (0.05–5%) to a nonselective recovery medium resulted in enhanced detection (12- to 465-fold) of AMW-stressedE.colias compared with recovery on the medium lacking these supplements, whereas addition of 3,3′-thiodipropionic acid failed to improve recovery. Additionalin vitroexperiments utilizing selective M-FC, mT7, and M-Endo media containing 1000 U catalase or 1.0% pyruvate similarly resulted in improved detection of AMW-stressed cells, with the exception of M-Endo containing pyruvate. Appropriately modified media were then used to analyze an AMW-impacted stream by the membrane filtration technique. Addition of catalase, pyruvate, or a combination of both significantly improved recovery of fecal and total coliforms without promoting growth of noncoliforms. Supplementation of plate count agar with pyruvate and (or) catalase enhanced detection of total heterotrophs. These findings suggest that addition of catalase or pyruvate to standard recovery media may improve detection of coliform and total heterotrophic bacteria in AMW-impacted waters.Key words: acid mine water, coliforms, stress.

ISSN:0008-4166    

DOI:10.1139/m90-095

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The kinetics of survival and inoculum potential ofFusarium oxysporumf. sp.liniwere studied in soil. Two types of inoculum were compared: microconidia freshly harvested from a laboratory-grown culture and microchlamydospores produced in sterilized soil. Introduced at the same inoculum densities into a natural soil, the two types of inoculum showed similar behaviour; the inoculum densities changed little with time, at least during 100 days. However, the two types of inoculum did differ in disease potential. A higher percentage of microchlamydospores than microconidia germinated in the rhizosphere of flax seedlings, and the heterotrophic fluorescein diacetate hydrolysing activity of the microchlamydospores was 100 times higher than that of microconidia. Moreover, the microchlamydospores produced more disease on flax than the microconidia even at a much lower inoculum density.Key words: survival, inoculum potential, enzymatic activity, conidia, chlamydospores,Fusarium oxysporum, soil.

ISSN:0008-4166    

DOI:10.1139/m90-096

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The inactivation of a large-focus-forming variant of hepatitis A virus (HM-175) by ozone was investigated. Experiments using mainly single-particle virus preparations suspended in phosphate–carbonate buffer were conducted over a range of pH levels (6–8) at 4 °C. Viral enumerations involved the use of a radioimmunofocus assay. While some tolerance to lower (i.e., 0.1–0.5 mg/L) ozone residuals was noted, the exposure of virus particles to ozone concentrations of 1 mg/L or greater at all pH levels resulted in their complete (5 log) inactivation within 60 s. The pH-related effects that were observed were not considered to be significant.Key words: hepatitis A virus, ozone, disinfection.

ISSN:0008-4166    

DOI:10.1139/m90-097

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

To study the response of natural communities of attached bacteria to Zn, artificial streams were dosed with Zn at levels of 0, 0.01,0.1,0.5, 1.0, and 10.0 mg/L in duplicate treatment groups. Changes in total biomass, chlorophyllacontent, total bacterial numbers, and heterotrophic activity were measured over a 5-week exposure period. The adaptation of the culturable bacterial community to Zn was assessed by comparing viable counts on unsupplemented medium with counts on media supplemented with several concentrations of Zn. The structure of that portion of the bacterial community capable of growth on nutrient agar was assessed by characterizing randomly selected colonies with respect to 20 nutritional capabilities and grouping the strains by numerical taxonomy. Streams receiving 0.5, 1.0, and 10.0 mg Zn/L were significantly inhibited with respect to all variables studied when compared with streams receiving 0, 0.01, or 0.1 mg Zn/L. Bacteria developed tolerance to the exposure concentration of Zn but were resistant to higher Zn concentrations. Increasing concentrations of Zn produced alterations in the structure of the culturable bacterial community, resulting in differing assemblages of bacterial groups and a decrease in diversity as measured by the Shannon–Wiener index and rarefaction. These results suggest that streams receiving 0.5 mg Zn/L or more may be adversely impacted.Key words: attached bacteria, zinc, heavy-metal resistance, species diversity.

ISSN:0008-4166    

DOI:10.1139/m90-098

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Eight strains of nonphytopathogenic agrobacteria, whose taxonomic positions are uncertain, were analyzed for their polyamine contents and their polyamine biosynthetic activities. They were separated into five types on the basis of polyamine distribution patterns. The first group contains putrescine, cadaverine, and spermidine as major polyamines, the second spermidine alone, the third cadaverine alone, the fourth putrescine, spermidine, spermine, homospermidine, and aminopropyl-homospermidine, and the last contains trace amounts of diaminopropane and spermidine. These polyamine patterns of eight species seem to suggest no close phylogenic relationship among these agrobacteria and are different from those of other typical, phytopathogenic species belonging toAgrobacterium.Key words: agrobacteria, decarboxylases, polyamines, homospermidine, aminopropylhomospermidine.

ISSN:0008-4166    

DOI:10.1139/m90-099

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

An anaerobic bacterial consortium was shown to carboxylate phenol to benzoate under methanogenic conditions. Benzoate accumulated in the culture medium and was completely degraded when the incubation period was prolonged. Two potential intermediates of phenol metabolism, namely cyclohexanol and cyclohexanone, were not accumulated or transformed by the consortium. Proteose peptone must be added to the culture medium for the carboxylation of phenol to occur and glucose could not replace proteose peptone. Inhibition of methanogenesis did not affect the carboxylation of phenol and the presence or absence of hydrogen in the gaseous atmosphere did not prevent the accumulation of benzoate. The consortium was composed of various microbiological forms dominated by Gram-negative rods. Phenol-carboxylating microorganisms were evaluated to about ≥ 1 × 108 cells/mL by using diluted inocula. These results suggest that the carboxylation of phenol is accomplished by co-metabolism and that proteose peptone or some degradation products serve as carbon and energy sources for the growth of the carboxylating bacteria, which appear to be present in large numbers in the consortium.Key words: phenol, degradation, anaerobic, consortium, methanogenesis.

ISSN:0008-4166    

DOI:10.1139/m90-100

出版商:NRC Research Press    

年代:1990

数据来源: NRC