摘要:

Candida albicansis a dimorphic yeast capable of producing alternate morphological forms (yeast or mycelium) in response to environmental changes. The intracellular level of glutathione, which helps to maintain the redox potential of the cell, is decreased significantly during the thermal induction of yeast-to-mycelium conversion. The reason for the decline of glutathione in the mycelial form is not understood. We have, therefore, investigated the levels of glutathione reductase, glutathioneS-transferase, γ-glutamyltranspeptidase, and glutathione peroxidase, four key enzymes involved in glutathione metabolism, in the yeast and mycelial forms. Yeast cells ofC.albicans3153A were induced in Lee's medium (pH 6.5) at 37 °C for 3 h to produce germ tubes. Cell lysates were prepared from yeast and mycelial cells, and glutathione reductase, glutathioneS-transferase, γ-glutamyltranspeptidase, and glutathione peroxidase were assayed spectrophotometrically. There was a 640% increase of the level of γ-glutamyltranspeptidase in the germ tubes as compared with the yeast cells. No other significant alteration of the levels of enzymes was noted. This increased activity of γ-glutamyltranspeptidase, which cleaves the glutamic acid residue of glutathione (Glu-Cys-Gly) appears to be, at least in part, responsible for the rapid decrease of the intracellular glutathione inC.albicansduring the yeast-to-mycelium conversion.Key words:Candida albicans, dimorphism, glutathione, glutathione reductase, glutathione peroxidase, γ-glutamyltranspeptidase.

ISSN:0008-4166    

DOI:10.1139/m96-011

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Carbazole is a nitrogen hetrocyclic compound associated with fossil fuels and their products. Enrichment cultures were established to isolate bacteria able to degrade carbazole and a plate assay was developed to select carbazole-degrading microorganisms from the enrichments. Three different bacterial isolates capable of mineralizing carbazole were obtained. No intermediates of carbazole degradation were detected. The bacteria had a limited substrate specificity; all used benzoate for growth but were unable to utilize the analogues of carbazole, fluorene, or dibenzothiophene.Key words: carbazole, biodegradation, bacteria.

ISSN:0008-4166    

DOI:10.1139/m96-012

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Azospirillumcells were inoculated in pregerminating wheat during seed imbibition. Surface-sterilized seeds ofTriticum aestivumcv. Buck Pucará were sequentially soaked for 3 h in water and 3 h in the inoculum of 3 × 108Azospirillum brasilenseSp 245 cells∙mL−1, to allow bacteria to enter during imbibition. Germination and seedling growth were accomplished in sterile distilled water at 20 °C, in the dark. To compare with more traditional methods based on plant–Azospirillumcolonization after germination, seedlings from noninoculated seeds were inoculated in parallel by immersing roots in the same inoculum, for the same period of time. Autoclaved inocula were used as controls in all cases. We observed about 5 × 108Azospirillumcells∙g−1fresh weight in 11-day-old wheat seedlings inoculated before or after seed germination. However, roots from seed-inoculated seedlings had higher both bacterial concentration and length. On the other hand, seeds inoculated during imbibition and dried to 14% water content retained 3.7 × 106viable cells∙g−1dry weight up to 27 days. Moreover, seeds stored for 30 days were not only able to germinate but also to harbor over 106cells∙g−1fresh weight in roots after 7 days growth. Here we present the possibility of obtaining in a simple and inexpensive way, seeds containing high numbers of viableAzospirillumcells, which could avoid the use of external carriers or adhesives.Key words:Azospirillum, wheat, inoc

ISSN:0008-4166    

DOI:10.1139/m96-013

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Recently, we reported the occurrence of seroconversion fromVibrio choleraenon-O1 toV.choleraeO1, but little is known about the environmental and physiological factors influencing seroconversion. We investigated effects of temperature (4, 25, and 35 °C) and salinity (<0.5 and 10‰), as well as the stage of growth of cells, on serogroup conversion. Seroconversion ofV.choleraeoccurred under various environmental conditions. However, the rate of seroconversion in natural water (<0.5‰ salinity) and synthetic seawater microcosms (10‰ salinity), employing cells harvested from stationary phase culture, was approximately 2 logs higher than cells harvested from cultures in the logarithmic phase (i.e., 105versus 103per 1010cells). Thus, the physiological state of the cells, and to a lesser degree, temperature and salinity, is an important factor in the conversion ofV.choleraefrom non-O1 to O1 serogroup.Key words:Vibrio choleraeO1,Vibrio choleraenon-O1, growth stage, serogroup conversion.

ISSN:0008-4166    

DOI:10.1139/m96-014

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Previous analyses of the two serotypes of infectious bursal disease virus (IBDV) have demonstrated the correlation between antigenicity and similarities of nucleotide and amino acid sequences of the VP2 coding region in genome segment A. Restriction fragment profiles of genomic segment A cDNA of five IBDV isolates (QC-2 and QT-1 of serotype 1, SK9, and Nos. 39 and 52 of serotype 2) were determined in order to establish the genetic relationship of these viruses to other avibirnaviruses. The restriction fragment profiles using three of seven restriction enzymes(Sadwhich cuts in the VP2 region,DraIII which cuts in the VP3 region, andEcoRI which cuts in the VP4 region) were used to place QC-2, QT-1, SK9, No. 39, and No. 52 within the phylogenetic tree among seven other avibirnaviruses of known sequence. The two IBDV serotypes corresponded to two genotypes on the basis of the presence or absence of theSacI restriction site. The serotype 1 cluster of strains was further differentiated into five minor clusters on the basis of thePstI,EcoRI,BamHI,HindIII,DraIII, andBsu36I restriction sites, which emphasized the geographical origins of the strains. It is concluded that restriction analysis of cDNA of the whole viral genomic segment A allows differentiation of IBDV isolates on the basis of their antigenicity and geographical origin.Key words: phylogeny, avibirnavirus, geographical origin.

ISSN:0008-4166    

DOI:10.1139/m96-015

出版商:NRC Research Press    

年代:1996

数据来源: NRC