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1.
The isolation and characterization of a rumen chitinolytic bacterium   总被引:1,自引:0,他引:1  
J.S. DICKSON, T.R. MANKE, i.v. WESLEY AND A.L. BAETZ. 1996. Arcobacter spp. have recently been genetically differentiated as a genus distinct from Campylobacter. Physiologically, Arcobacter spp. are aerotolerant bacteria, while Campylobacter spp. are microaerophilic. However, since Arcobacter spp. have been difficult to grow to high population densities in broth media, alternative culture techniques were investigated. A biphasic culture system was developed in 25 cm2 tissue culture flasks. Biphasic culture, consisting of a solid phase of 10% bovine blood agar and a liquid phase of Brain Heart Infusion broth, was found to increase bacterial population densities by more than 2 log10 cycles for strains of A. butzleri and A. skirrowii. A strain of A. cryaerophilus , which was non-culturable in broth culture, attained population densities of 109 cells ml-1 in biphasic culture. Neither the addition of fetal bovine serum to the liquid nor an increase in the surface area from 25 to 75 cm2 resulted in increased cell densities.  相似文献   

2.
Thermophilic obligately autotrophic H2-oxidizing bacteria from Icelandic hot springs were tested for growth on thiosulfate. Ten strains were tested and all grew on thiosulfate but not on sulfite or sulfur. The product of thiosulfate oxidation was sulfate. The growth rate on thiosulfate was slower (μ=0.12 h-1) than on H2 (μ=0.34 h-1). Washed cells which had been grown on thiosulfate could oxidize thiosulfate rapidly but H2-grown cells oxidized thiosulfate much more slowly and with about a 3 h lag time. The bacteria would not grow on agar medium under H2 but grew on agar medium containing thiosulfate.  相似文献   

3.
Abstract Monolayers of epithelial cells obtained by culture of isolated secretory alveoli from the bovine mammary gland were used as target cells in bacterial adhesion assays. The ability of two strains of Streptococcus uberis (EF20 and 0140J) to adhere to these cells was examined using scanning electron microscopy (SEM). The cultured monolayers consisted of two types of epithelial cell one of which possessed many microvilli and another which exhibited only sparse or no microvilli. Strain EF20 adhered more readily and in greater numbers to the cells without microvilli (MV) than to cells possessing microvilli (MV+). Strain 0140J also interacted with a greater proportion of MV cells but adhered to both MV and MV+ cell types in similar numbers.  相似文献   

4.
5.
Ten type 1 fimbriate strains of Enterobacteriaceae were examined in an in vitro adhesion assay with HEp2 epithelial cells. The range of HEp2 cell adhesiveness, which was characteristic for each strain, was affected by motility, type 1 fimbriation and production of mannose sensitive haemagglutinin. Nevertheless, not all type 1 fimbriate strains adhered well in this model. The findings are discussed with regard to the possibility that different type 1 fimbriate enterobacteria, though all are mannose sensitive, recognize different mannose-containing receptors present or available on the surfaces of the HEp2 cells.  相似文献   

6.
Ten type 1 fimbriate strains of Enterobacteriaceae were examined in an in vitro adhesion assay with HEp2 epithelial cells. The range of HEp2 cell adhesiveness, which was characteristic for each strain, was affected by motility, type 1 fimbriation and production of mannose sensitive haemagglutinin. Nevertheless, not all type 1 fimbriate strains adhered well in this model. The findings are discussed with regard to the possibility that different type 1 fimbriate enterobacteria, though all are mannose sensitive, recognize different mannose-containing receptors present or available on the surfaces of the HEp2 cells.  相似文献   

7.
Epithelial cells are the initial sites of host invasion by group A Streptococcus pyogenes (GAS), and their infection of epithelial cells has been suggested to induce apoptosis. However, the mechanism responsible for bacteria–host interaction and the induction of apoptosis has not been clearly understood. We demonstrate here that human pharyngeal epithelial HEp-2 cells became apoptotic with DNA fragmentation by invasion of GAS strains JRS4 (M6+, F1+) and JRS145 (M6, F1+ mutant of JRS4), whereas apoptotic cellular changes were not observed in SAM1 (M6+, F1 mutant) or SAM2 (M6, F1 mutant) infected HEp-2 cells. Confocal microscopy revealed that Bax translocation to mitochondria and cytochrome c release occurred after 4 h of infection. Western blot analyses showed that the amounts of Bcl-2 and Bcl-xL were decreased in the mitochondria of infected cells. In addition, we demonstrated that the release of nuclear histone from infected cells was prevented by the addition of caspase-9 inhibitor (Ac-LEHD-CHO). We conclude that the internalization of GAS in epithelial cells is necessary and sufficient for the induction of apoptosis, which is initiated by mitochondrial dysfunction, and the mechanism of GAS-induced apoptosis is clearly different from that induced by other intracellular invasive bacteria, e.g. Shigella and Salmonella species.  相似文献   

8.
The pathogenic activities in vitro and in vivo of live bacteria and extracellular products (ECP) of 24 motile Aeromonas strains were investigated. Most Aer. hydrophila and Aer. jandaei isolates were pathogenic for eels (LD50 105·4-107·6 cfu fish-1) but no Aer. sobria , Aer. caviae and Aer. allosaccharophila caused mortality in eels at doses of > 108·4 cfu fish-1. Of these Aeromonas strains, Aer. hydrophila and Aer. jandaei in particular produced elastases and haemolysins against fish erythrocytes. ECP from Aer. hydrophila and Aer. jandaei caused degenerative changes in fish cell lines and were strongly toxic for eels (LD50 1·0–3·2 μg (g fish)-1) reproducing the symptoms associated with natural disease. ECP from non-pathogenic species were inactive on fish cell lines as well as being poorly lethal for eels (LD50 > 9·2 μg (g fish)-1). All these biological activities of Aeromonas ECP were lost after heat treatment. These findings indicate differences between pathogenic and non-pathogenic Aeromonas species with respect to the expression of virulence factors, and show that elastases, haemolysins and exotoxins play a leading role in the pathogenicity of motile Aeromonas for eels.  相似文献   

9.
Abstract Sulfate-reducing bacteria were enumerated in soils and water samples from Senegal ricefields using lactate and sulfate as substrates. When rice plants were severely injured by sulfides, maximum densities ranged from 107 to 109 bacteria g−1 of dry spermosphere or rhizosphere soil. Seven non-sporulating, mesophilic strains were isolated. The strains had motile curved cells and stained Gram-negative. Lactate, pyruvate, H2+ CO2, malate, fumarate, or ethanol could serve as electron donors. Organic acids were incompletely oxidized to acetate. Alcohols were degraded to the corresponding fatty acids. Sulfate, sulfite, or thiosulfate could serve as electron acceptors and were reduced to sulfide. Vitamins, yeast extract, Biotrypcase, or additional NaCl were not required for growth. On the basis of morphological and physiological properties, and the G + C mol % of the DNA, six isolates were identified as Desulfovibrio vulgaris and one as Desulfovibrio desulfuricans . The comparison of their main physiological properties with the physico-chemical properties of sampling sites indicated that they were better adapted to conditions prevailing in the rice rhizosphere than to those prevailing in the bulk of soil.  相似文献   

10.
Many exopolysaccharide (EPS)-producing bacterial strains also synthesize storage polymers. The production of slime EPS and of the storage polymer glycogen was compared in batch cultures of EPS+ and EPS- isogenic strains of Enterobacter aerogenes type 8. Conditions of nutrient imbalance with high C: N ratios favoured both EPS and storage polymer synthesis and resulted in little subsequent degradation of glycogen. In the EPS+ strain, glycogen synthesis was consistently lower than in the EPS- strain, indicating that substrate was preferentially used for EPS production. Reduced levels of carbon substrate in the growth medium resulted in lower storage polymer synthesis and in the degradation of the glycogen formed in EPS-producing bacteria. Considerable differences in the synthesis and breakdown of intracellular carbohydrate were observed between bacteria grown in synthetic media with ammonium salts and the same bacteria grown in medium with casein hydrolysate as the nitrogen source. Growth in media depleted in magnesium was slower than in complete media but high yields of glycogen were obtained in both the EPS+ and EPS- strains.  相似文献   

11.
Surface free energies of oral streptococci and their adhesion to solids   总被引:1,自引:0,他引:1  
Abstract The adhesion of 3 strains of oral streptococci from a buffered suspension onto 3 different solid substrata was studied. Representative strains of streptococci were selected on the basis of their surface free energy ( γ b), namely Streptococcus mitis L1 ( γ b= 37 mJ·m−2), Streptococcus sanguis CH3 (95 mJ·m−2) and Streptococcus mutans NS (117 mJ·m−2). Solid substrata were also selected on basis of their surface free energy ( γ s), and included polytetrafluorethylene ( γ s= 20 mJ·m−2), polymethylmethacrylate (53 mJ·m−2) and glass (109 mJ·m−2). Bacterial adhesion was measured as the number of bacteria adhering per cm2 at equilibrium. Equilibrium was usually obtained within 20 min. S. sanguis CH3, having an intermediate surface free energy did not show a clear preference for any of the 3 solids. S. mitis L1, however, the lowest surface free energy strain, adhered in highest numbers to the low energy solid PTFE, whereas the highest γ b strain, S. mutans NS, adhered in highest numbers to the highest γ s solid, glass. Calculation of the interfacial free energy of adhesion ( ΔF adh) for each bacterial strain showed that this parameter was predictive of bacterial adhesion to solid substrata.  相似文献   

12.
The growth of a strain of Rhizobium trifolii and of R. meliloti was studied in broth and peat cultures to determine the relative toxicity of Na+ and Cl-. The following salts were added in a range of concentrations: Na2HPO4 as a source of Na+, CaCl2.2H2O as a source of Cl-, and NaCl. Disodium hydrogen orthophosphate affected the growth rate of both strains in broth culture but not in peat culture. Unexpectedly, calcium chloride was more toxic than NaCl in broth and peat culture. The toxicity of NaCl can be ascribed to the Cl-. Rhizobium meliloti strains grew on 3·5% NaCl after adaptation during a long period. Rhizobia for soya bean and cowpea grew at 0·5% NaCl and those for clover and pea, at 1·0% NaCl.  相似文献   

13.
Abstract Transport of Mn2+ was repressed in Candida utilis cells grown in continuous culture in high-Mn2+ (100 μM Mn2+) medium as compared to cells grown in basic (0.45 μM Mn2+) and low-Mn2+ (< 0.05 μM Mn2+) media. In contrast, no repression of Cu2+ uptake occurred in high-Cu2+-grown (25 μM Cu2+) cells as compared to cells grown in basic medium (0.54 μM Cu2+). Cu2+-limited cells did not hyperaccumulate Cu2+ and there was not significant difference in initial uptake rates for all 3 Cu2+ conditions. Mn2+ uptake appears to be regulated by a mechanism sensitive to the external Mn2+ concentration, whereas Cu2+ transport is not governed in this way by the external Cu2+.  相似文献   

14.
There were significant levels of in vitro hydrogenase activity in Methanosarcina strains. The multiple forms of hydrogenase were observed in cell free extracts of cells grown on methanol. Strains having poor growth on H2 : CO2 had four forms while strains having normal growth on all substrates contained two forms of hydrogenase. These multiple forms differ in their charges as well as in their composition of transition metal ions. The strain having normal growth showed higher incorporation of 63Ni2+ and 65Zn2+. Both hydrogenases, A and D, of strain P3 had methylviologen and F420-reducing activity and contained Zn2+ and Co2+ respectively. Hydrogenases A and D of strains P1 and P4 also had similar characteristics whereas hydrogenases B and C had only methylviologen reducing activity.  相似文献   

15.
The reaggregation kinetics of frog ( Xenopus laevis ) cells prepared using several different dissociation procedures were monitored. Two distinct modes of cell adhesion were revealed, one mediated by Ca2+ dependent cell-cell adhesion system (CDS) and the other mediated by Ca2+ independent one (CIDS).
CDS was detected in frog embryonic (two-cell stage to neurula) cells and in cells of epithelial cell lines (A6 and A8), while CIDS was detected only in A6 cells. Frog CDS was resistant to 0.01% tryptic digestion in the presence of 1 mM Ca2+ and CIDS was resistant to dilute (0.0001%) tryptic digestion. Cells with both mechanisms were prepared by dissociation with 1 mM EDTA and both mechanisms were absent in cells dissociated with 0.01% trypsin and 1 mM EDTA. Frog CDS and CIDS functioned in a temperature dependent and independent manner, respectively. Properties of frog CDS and CIDS revealed in this study were the same as those of mammalian or avian CDS and CIDS, respectively. Frog cells with CDS cross-adhered to mammalian epithelial (F9) cells but not to fibroblastic (V79) cells Ca2+ dependently. Monoclonal antibody ECCD-1 raised against mouse epithelial CDS blocked aggregation of frog A8 cells.
These results suggest the similarity between frog CDS and mammalian epithelial type CDS.  相似文献   

16.
The adhesive capability of Vibrio cholerae 01 strains to isolated rabbit intestinal epithelial cells was maximally expressed when the bacteria were grown in synthetic broth and was enhanced by the presence of Ca2+ in the growth media. N-Acetyl-D-glucosamine could inhibit the adhesion of the bacteria to rabbit intestinal epithelial cells as could lipopolysaccharide O-antigen from Vibrio cholerae 01 and lectin from Triticum vulgaris. Since the lipopolysaccharide is known to contain N-acetyl-D-glucosamine and because the lectin from Triticum vulgaris shows specificity for this sugar, it is probable that N-acetyl-D-glucosamine is actively involved in the adhesion of Vibrio cholerae 01 to isolated rabbit intestinal epithelial cells.  相似文献   

17.
Z. LAZIM, T.J. HUMPHREY AND R.J. ROWBURY. 1996. Organisms grown in low salt broth (LSB) are acid resistant but become sensitive on growth for 30-60 min with 300 mmol 1−1 added NaCl. Salt-induced acid sensitivity only occurs in relA+ strains and sensitization is abolished by glucose, this catabolite repression effect being reversed by cAMP. The finding that sensitization did not occur in a phoE strain but did occur in a phoE+ derivative of it suggested that the response might result from PhoE induction, since PhoE acts as the major outer membrane (OM) proton pore under most conditions. In agreement with this, low-salt broth (LSB)-grown cells of a chromosomally lac strain carrying pJP102 ( phoE-lacZ ) produced low levels of β-galactosidase but growth with added NaCl led to rapid and appreciable induction. Also, a phoA mutant carrying a phoE-phoA fusion produced little alkaline phosphatase after growth in LSB but much more in LSB with added NaCl. Increased β-galactosidase synthesis (in phoE-lacZ strains) in the presence of NaCl was abolished by glucose, this effect being reversible by cAMP, and there was more NaCl-induced synthesis of this enzyme in relA+ strains.
Accordingly, it appears that addition of NaCl to LSB leads to acid sensitivity because it induces synthesis of the OM proton pore PhoE.  相似文献   

18.
Abstract Non-cytotoxic and non-antimicrobial concentrations of an artificial surfactant inhibited the adhesion of 14C-radiolabelled Klebsiella pneumoniae WG14 to embryonic lung epithelial cells L-132. The minimal antiadhesive concentration was 200 ng · ml−1. In a dynamic adhesion test model, already adhering bacteria were removed from the epithelial cell surface by the surfactant. The antiadhesive action might be based on protection of the epithelial cells.  相似文献   

19.
The nitrate reductase (NR, EC 1.6.6.1) activity in root nodules formed by hydrogenase positive (Hup+) and hydrogenase negative (Hup) Rhizobium leguminosarum strains was examined in symbioses with the pea cultivar Alaska ( Pisum sativum L.), Rates of activity were determined by the in vivo assay in nodules from plants that were only N2-dependent or grown in the presence of 2 m M KNO3. The rates varied widely among strains, regardless of the Hup phenotype of the R. leguminosarum strain used for inoculation, but the overall results indicated that nodules formed by Hup strains accumulated more nitrite in the incubation medium than did those with Hup phenotypes. Total plant dry weight and reduced nitrogen content of pea plants grown in the presence of 2 m M KNO3 and inoculated with single Hup+ and Hup R. leguminosarum strains were statistically different among some strains. These observations suggest that the possible advantages derived from the presence of the Hup system on whole plant growth may be counteracted by the higher rates of NR activity in the Hup strains in the R. leguminosarum -pea symbiosis.  相似文献   

20.
Dimethylsulfoxide reduction by marine sulfate-reducing bacteria   总被引:2,自引:0,他引:2  
Abstract Dimethylsulfoxide (DMSO) reduction occurred in five out of nine strains of sulfate-reducing bacteria from marine or saline environments, but not in three freshwater isolates. DMSO reduction supported growth in all positive strains. In Desulfovibrio desulfuricans strain PA2805, DMSO reduction occurred simultaneously with sulfate reduction and was not effectively inhibited by molybdate, a specific inhibitor of sulfate reduction. The growth yield per mol lactate was 26% higher with DMSO than with sulfate as electron acceptor. In extracts of cells of strain PA2805 grown on sulfate, a low level of DMSO-reducing activity was present (0.013 μmol (mg protein) min); higher levels were found in cells grown on DMSO (0.56 μmol (mg protein) min). In anoxic marine environments DMSO reduction by sulfate-reducing bacteria may lead to enhanced dimethylsulfide emission rates.  相似文献   

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