摘要:

The variation in the levels of thermotolerant coliforms has been measured at various time–space observation scales in a marine coastal ecosystem (Thau pond). The spatial distribution of the bacteria was organized in the ecosystem (observation distance ≈1 km) in the form of either spots or gradients. The latter only appeared after massive drifts from the watershed. A strong local variation (< 1 km) was permanently associated with a broader observation scale. Local variation can develop from rapidly decreasing gradients in the levels of thermotolerant coliforms, starting from the drift points of the watershed. The variation with time was high whatever the observation frequency (monthly, daily, hourly). Monthly sampling usually revealed higher bacterial counts during winter compared with summer. During winter, the daily and hourly degree of variation of the bacterial levels was comparable and the populations were organized according to a linear trend. In summer time, there was a higher degree of variation in the populations and hourly variations can show cyclic trends (diurnal minima and nocturnal maxima). Our results show that privileged sampling scales occur and should be considered when evaluating the impact of environmental parameters (sun exposure, role of the watershed… ) and trying to correlate them. These results also enabled us to define a better sampling strategy for the detection of thermotolerant coliforms in such an ecosystem.Key words: thermotolerant coliforms, marine coastal ecosystem, spatial distribution, variation with time, sampling. [Journal translatio

ISSN:0008-4166    

DOI:10.1139/m90-055

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Apiotrichum curvatumATCC 20509, an oleaginous yeast that can accumulate up to 60% of its cellular dry weight as intracellular lipid when grown with excess carbon, was grown in nitrogen-limited, balanced, and lactose-free medium with asparagine as nitrogen source and lactose as carbon source. Biomass and lipid accumulation were measured, cell composition was analyzed, and catalase activity was followed as marker enzyme for peroxisomes. The organism accumulated 54% of its dry weight as total cellular lipid when grown under nitrogen limitation and accumulated only 20–25% of its dry weight as lipid when grown in balanced medium. When starved for carbon, cells utilized endogenous lipid and carbohydrate as carbon and energy sources; the intracellular contents of lipid and carbohydrate decreased by 31 and 26%, respectively. Intracellular carbohydrates also seemed to be used as intermediates for lipid accumulation and lipid turnover. Catalase activity was strongly induced (over 10-fold increase in specific activity) when cells metabolized endogenous lipid. The lipid content of cells was inversely related to catalase activity and to intracellular protein or total nitrogen content. Lipid content showed no correlation with intracellular carbohydrate content.Key words: lipid, peroxisomes, oleaginous,Apiotrichum curvatum.

ISSN:0008-4166    

DOI:10.1139/m90-056

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Aquaspirillum sinuosumcell walls bear two paracrystalline, proteinaceous surface layers (S layers). Each shows a different symmetry: the inner layer is closely apposed to the outer membrane and is a tetragonal array (90° axes; 5-nm units; repeat frequency 8 nm); the outer layer is a hexagonal array on the external surface (14-nm units; repeat frequency 18 nm) and, although the units have a six-pointed stellate form, the linkage between units is not resolved. The outer layer consists of a major 130-kDa protein and a 180-kDa minor component; these co-extract, co-assemble, and are inseparable by hydroxylapatite chromatography or by recrystallization. The solubilizing effects of reagents suggest stabilization by hydrogen bonding and Ca2+. The two outer layer proteins are serologically related and show partial identity by peptide mapping. Periodic acid – Schiff staining of the 180-kDa band suggests that this may be a glycosylated form of the 130-kDa component. The inner layer components form a doublet of 75- and 80-kDa polypeptides with extreme resistance to extraction. Close apposition to the outer membrane, resistance to chaotropes, aqueous insolubility, and behaviour in charge-shift electrophoresis suggest hydrophobic interaction between subunits and an integral association with the outer membrane.Key words: bacterial surface, cell wall, surface layers, cell-wall proteins, cell-wall assembly.

ISSN:0008-4166    

DOI:10.1139/m90-057

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The effect of growth temperature on the binding ofCandida albicansto human buccal epithelial cells (BECs) was examined using an equilibrium of binding analysis.Candida albicanswas cultured in M9 medium either for 12 h at 25 °C or for 9 h at 25 °C and then shifted to 37 °C for 3 h. The temperature shift did not result in germ tube formation; however, the adherence ofC.albicansto BECs was altered. Shifting temperature increased the yeast's ability to bind to BECs. A Langmuir adsorption isotherm was used to calculate the maximum number of available binding sites (N) and the apparent association constants of binding (Ka) for all resolvable adhesin–receptor interactions. Three classes of adhesin–receptor interactions were resolved when the yeast was cultured at 25 °C and included a low copy number site (N = 3.0 cfu/BEC;Ka = 2.11 × 10−6 mL/cfu), a medium copy number site (N = 23.6 cfu/BEC,Ka = 8.21 × 10−7 mL/cfu), and a high copy number site (N = 91.7 cfu/BEC,Ka = 3.35 × 10−8 mL/cfu). Two classes of adhesin–receptor interactions were resolved when the incubation temperature was shifted to 37 °C: a low copy number site (N = 4.5 cfu/BEC,Ka = 3.98 × 10−6 mL/cfu) and a high copy number site (N = 150.5 cfu/BEC,Ka = 8.47 × 10−8 mL/cfu). AugmentedC.albicansadherence to BECs due to the elevated growth temperatures appears to result from a temperature-regulated alteration in theC.albicansadhesin that recognizes a high copy number receptor site with relatively low affinity.

ISSN:0008-4166    

DOI:10.1139/m90-058

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The whole human cytomegalovirus strain AD169 genome was cloned into plasmid pAT153 in the form of 25HindIII fragments. Double and triple digestions of the recombinant plasmids with restriction endonucleasesBamHI,BglII,ClaI,DraI,EcoRI,EcoRV,HindIII,HpaI,KpnI,PaeR7,PstI,SphI andXbaI yielded a detailed restriction map of human cytomegalovirus DNA. Knowing the exact position of numerous restriction sites in the viral DNA molecule, we have been able to examine very closely the heterologous region between the long and the short segments of the human cytomegalovirus genome.Key words: DNA, physical map, cytomegalovirus, restriction endonucleases, HCMV.

ISSN:0008-4166    

DOI:10.1139/m90-059

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Transformation of pBR322 DNA intoShigellaoccurred at a low frequency. The efficiency of transformation was highest inS.dysenteriae1 and lowest inS.flexneri. Treatment of cells with CaCl2for a prolonged period (24 h) increased the efficiency of transformation in all strains, except inS.flexneri, where transformation efficiency could not be improved by a variety of manipulations. Transformation efficiency did not increase in any of the strains when transformation was carried out with plasmid DNA obtained from a transformant (homologous transformation), suggesting the absence of a strong restriction–modification system. Extracellular deoxyribonuclease (DNase) levels were low in all the strains tested, but the levels of endogenous DNase, released after CaCl2treatment or sonication of the cells, were high. Washing the cells with a solution of CaCl2did not enhance transformation, suggesting that endogenous DNase could be a significant factor affecting transformation efficiency in species ofShigella.Key words:Shigella, transformation, plasmid DNA.

ISSN:0008-4166    

DOI:10.1139/m90-060

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Over 250 isolates ofFusarium oxysporumcollected from infected watermelon plants and soil samples from a pathogen-infested field, as well as known isolates ofF.oxysporumf. sp.niveumimported from various locations around the world, were tested for pathogenicity on watermelon and used to determine vegetative compatibility groups (VCGs) withinF.oxysporumf. sp.niveum. Vegetative compatibility was assessed on the basis of heterokaryon formation among nitrate-nonutilizing mutants. Race determinations were made by screening isolates on six different watermelon cultivars of varying resistance. All isolates ofF.oxysporumf. sp.niveumbelonged to one of three distinct VCGs, and were incompatible with isolates that were not pathogenic on watermelon. Isolates ofF.oxysporumf. sp.niveumwere subdivided into two races and there was a direct relationship between VCG and race. VCG 0080 consisted of race 1 isolates from five states of the United States, Taiwan, and Australia. VCG 0081 consisted solely of race 1 isolates from Florida. VCG 0082 was comprised solely of race 2 isolates, all of which were capable of causing severe wilt on all cultivars tested. Numerous Florida isolates were compatible with race 2 isolates from Texas and demonstrated comparable virulence on all cultivars, confirming the presence of race 2 in Florida. WithF.oxysporumf. sp.niveum, vegetative compatibility can be utilized as an alternative or collaborative method to distinguish pathogenic from nonpathogenic strains ofF.oxysporumand to differentiate subforma specialis virulence characteristics.Key words: fusarium wilt,nitmutants, watermelon.

ISSN:0008-4166    

DOI:10.1139/m90-061

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Human papillomavirus deoxyribonucleic acid was detected in prostate tissue from patients with benign prostatic hyperplasia or prostatic carcinoma. Radiolabelled genomic probes, specific for the sexually transmitted human papillomavirus types 16 and 18, were used to detect viral genomic sequences in prostate DNA samples analyzed by the Southern blot technique. Viral sequences were identified in DNA from 7 of 16 prostate samples including both hyperplastic and carcinoma tissues and including tissues obtained by transurethral resection or suprapubic prostatectomy. These data indicate that the prostate gland can be infected with human papillomavirus and imply that the prostate may act as a reservoir for the sexual transmission of papillomavirus via seminal fluid. The detection of both episomal and integrated viral DNA sequences in prostate tissue may have important implications for the etiology of prostate disease.Key words: human papillomavirus, prostate, hyperplasia, carcinoma, Southern blot.

ISSN:0008-4166    

DOI:10.1139/m90-062

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The aggregation ofActinomyces viscosusandActinomyces naeslundiiwith extracellular vesicles ofBacteroides gingivaliswas studied. Factors influencing the aggregation phenomenon were examined.L-Arginine was found to effectively inhibit aggregation as was an antibody preparation directed against aB.gingivalissurface hemagglutinin. Aggregation occurred over a wide pH range and did not seem to be affected by high salt concentrations or the presence of carbohydrates. Treatment of the vesicle preparation with proteases, sodium dodecyl sulphate, and high temperatures diminished or eliminated aggregation, while similar treatment of theActinomyceshad no effect on aggregation.Key words: vesicles, outer membranes, aggregation, oral bacteria.

ISSN:0008-4166    

DOI:10.1139/m90-063

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

InPhysarum flavicomumBerk., growing amoebae convert to dormant cysts under conditions of nutrient imbalance. Exogenous adenine inhibits the process and the cells produce an elevated intracellular concentration ofS-adenosylmethionine. Evidence indicates that the increased level ofS-adenosylmethionine is responsible for the disruption of the normal developmental process. One of the biological functions ofS-adenosylmethionine is in polyamine synthesis and it is known that a well-controlled intracellular concentration of polyamines is essential for normal cell growth and differentiation. In this study, high-performance liquid chromatography was used to determine the intracellular polyamine patterns in growing cells, adenine-treated and normal encysting cells, and dormant cysts. Putrescine and spermidine were the most abundant polyamines found in the cells; growing cells had the highest level, adenine-treated cells had a 1.5 to 2.0 times higher level than normal encysting cells, while cysts had the lowest (only 3 and 12% of that of growing cells). Cadaverine andN1-acetylspermidine were found in all the cells and their levels decreased during encystment. Acetylputrescine was found in growing cells only and acetylspermine was found in all cells except cysts. Acetylcadaverine,N8-acetylspermidine, 1,3-diaminopropane, and spermine were not detected in any of the cells.Key words: polyamines, encystment,Physarum flavicomum, amoebae, cysts, growing, dormant, differentiation, development.

ISSN:0008-4166    

DOI:10.1139/m90-064

出版商:NRC Research Press    

年代:1990

数据来源: NRC