- Volume 140, Issue 5, 1994
Volume 140, Issue 5, 1994
- Pathogenicity And Medical Microbiology
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Involvement of cell wall glucans in the genesis and persistence of the inflammatory reaction caused by the fungus Paracoccidioides brasiliensis
More LessThe role of cell wall polysaccharides in leucocyte recruitment and granuloma formation in paracoccidioidomycosis was investigated. The inflammatory cells recruitment to the peritoneal cavity in rats inoculated with cell wall fraction (CW-265 or F1-265) from an avirulent strain of Paracoccidioides brasiliensis (Pb265), was greater than that observed for the cell wall fraction (CW-HC or F1-HC) recovered from the virulent strain (PbHC). Moreover, the inoculation of F1-HC and F1-265 into the subcutaneous layer of mice resulted in the formation of nodular and not progressive granulomatous lesions. The size and mean time of evolution of these lesions was proportional to the degree of virulence of the sample from which they were derived. Analyses showed that both F1 fractions contained β-glucan and chitin. Only β-glucan was able to trigger attraction and concentric organization of polymorphonuclear neutrophils and macrophages at the inflammatory foci, and the difference in the concentration of this compound in the cell walls of PbHC and Pb265 could explain the inflammatory capacity exhibited by the two strains of P. brasiliensis.
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Genotype and phenotype of oral Candida albicans from patients infected with the human immunodeficiency virus
More LessCandida albicans has been shown to vary in its phenotypic expression with the progression of human immunodeficiency virus (HIV) infection. Isolates of C. albicans were obtained from 45 patients with HIV infection during the progression of their disease and differentiated using two methods. The first utilized the morphological characteristics of colonies, and the second method utilized a small portion of C. albicans DNA as a probe on Southern-transferred, EcoRl-digested C. albicans genomic DNA. In 67% of the patients a single strain of C. albicans, as determined by the DNA analysis, was isolated from each individual. The phenotypic expression of the genetically identical strains varied considerably over the experimental period with one morphotype being predominant. These results showed that the genotype of C. albicans persisted in the majority of HIV-infected individuals, but that the phenotypical expression of this strain changed. A novel finding in this study was that 18 strains of C. albicans had DNA which did not hybridize to the probe used.
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recA mutations reduce adherence and colonization by classical and El Tor strains of Vibrio cholerae
Two recA mutants of Vibrio cholerae (classical and El Tor biotypes) were constructed by disruption of the wild-type recA gene with mutated recA sequences of V. cholerae cloned in the suicide vector pGP704. Mutants defective in the recA gene were compared with their respective RecA + parent strains with regard to their adherence to isolated rabbit intestine and colonization of intestine of infant mice. The recA mutation in V. cholerae was found to diminish adherence and markedly affected colonization.
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- Physiology And Growth
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Weak acid preservatives block the heat shock response and heat-shock-element-directed lacZ expression of low pH Saccharomyces cerevisiae cultures, an inhibitory action partially relieved by respiratory deficiency
More LessInhibition of microbial growth by weak acid preservatives increases with medium acidification, since these agents enter cells in the undissociated state. Many of the effects of these acids are due to the cytoplasmic acidification they cause as they dissociate in the higher pH environment of the cytosol. Sorbic and benzoic acids, two widely used preservatives, were found to exert pronounced effects on the heat shock response and thermotolerance of Saccharomyces cerevisiae. These effects were strongly influenced by the pH of the culture medium. In low pH cultures sorbate inhibited the induction of thermotolerance by sublethal heat shock, causing strong induction of respiratory-deficient petites among the survivors of heat treatment. However, when the culture pH was above 5·5 sorbate acted as a powerful chemical inducer of thermotolerance in the absence of any sublethal heat treatment. Sorbate and benzoate also inhibited heat induction of the major heat shock proteins in low pH yeast cultures. This appears to result from lack of induction of the heat shock element (HSE) promoter sequence since sorbate prevented heat induction of a HSE-lacZ fusion at low pH. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and the plasma-membrane-ATPase inhibitor diethylstilboestrol were identified as additional inhibitors of heat induction of heat shock proteins. Numerous chemicals induce the heat shock response in the absence of heat stress, but sorbate, benzoate, CCCP and diethylstilboestrol are the first compounds shown to act as selective inhibitors of heat-induced protein expression in yeast. In the presence of sorbate concentrations which, at low pH, totally inhibit both the heat shock response and growth of cells competent in respiration, respiratory-deficient petites still retain a limited capacity for growth and for heat induction of heat shock proteins. This restoration of a response to heat shock in acidified sorbate-treated cultures of petites might contribute to their higher capacity for growth in the presence of sorbate.
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A surface lectin associated with flocculation in brewing strains of Saccharomyces cerevisiae
More LessA cell-wall-surface protein purified from the cells of Saccharomyces cerevisiae NCYC 227 was found to be involved in the non-sexual flocculation of this yeast. This 13 kDa protein was found to bind specifically to mannose. The protein bound to mannans isolated from yeast as well as in situ to intact cells, but only in the presence of calcium ions. The protein, a mannoprotein, formed aggregates as revealed in SDS-PAGE. Urea and higher temperatures prevented protein aggregation, suggesting that the flocculation of S. cerevisiae is primarily due to hydrogen bonding between mannan and protein.
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Glucose transport by the phosphoenolpyruvate: mannose phosphotransferase system in Lactobacillus casei ATCC 393 and its role in carbon catabolite repression
More LessA 2-deoxy-d-glucose-resistant mutant of a pLZ15-cured derivative of Lactobacillus casei ATCC 393 was isolated on agar medium containing 10 mM 2-deoxy-d-glucose and 5 g lactose 1-1 The mutant was impaired in the main glucose transport mechanism, a PTSman-type system. Additionally a proton-motive-force-dependent glucose permease was detected. The growth response and the sugar consumption rates of the wild-type and the PTSman-deficient mutant suggested that the mutated element of the complex IIABCman was, in the wild-type, responsible for a strong repression by glucose and mannose of the lactose and ribose assimilation genes, while assimilation of galactose was only weakly repressed. It is postulated that they are regulated by a different mechanism of catabolite repression.
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The psi operon of Rhizobium leguminosarum biovar phaseoli: identification of two genes whose products are located at the bacterial cell surface
More LessWe have delineated three short open reading frames, psiA, ORF-P and psiB within the psi operon of Rhizobium leguminosarum biovar phaseoli. psiA, in a multi-copy plasmid, causes inhibition of exopolysaccharide synthesis in R. leguminosarum. In addition, the suppression of exopolysaccharide synthesis due to the multi-copy psiA caused R. leguminosarum strains to stain with the dye calcofluor, a response that does not occur with wild-type strains of this species. Insertions of a defective phoA gene (lacking its promoter, ribosomal binding site and leader sequence) into psiA and psiB were isolated and the precise locations of the insertions were established. PsiA-PhoA and PsiB-PhoA protein fusions were found to express alkaline phosphatase activity indicating that PsiA and PsiB span the inner membrane or are translocated across it.
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Effects of organic acids and low pH on Rhizobium meliloti 104A14
More LessIn the symbiotic relationship between Rhizobium meliloti and alfalfa (Medicago sativa), the bacteria are enclosed within the plant cell by a membrane that may function like a plant vacuolar membrane and maintain a pH between 5·5 and 6·0. Free-living Rhizobium meliloti 104A14 is sensitive to pH in this range and its sensitivity was influenced by the presence of acetate and other monocarboxylic acids. R. meliloti can grow at pH 6·0 in 3 mM succinate but does not grow at pH 6·2 if 10 mM acetate is added. The combination of low pH and acetate is bacteriostatic. Measurement of internal pH (pHi) using 14C-labelled benzoate as a permeant acid showed that growth inhibition occurs when pHi falls below 7·15.
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- Systematics
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Characterization of Bacillus thuringiensis and related bacteria by ribosomal RNA gene restriction fragment length polymorphisms
More LessRibosomal RNA gene restriction patterns have been determined for 43 strains of Bacillus thuringiensis representing 10 serovars and eight reference strains of B. anthracis, B. cereus and B. mycoides. Strains within a B. thuringiensis serovar produced highly related or identical ribotype patterns: in particular, 12 strains of serovar israelensis, five strains of serovar kurstaki, two strains of serovar galleriae and three strains of serovar aizawa produced ribotype patterns consistent with serotype designations. Moreover, variety tenebrionis (serotype 8a8b), a coleopteran pathogen, could be distinguished from the more common lepidopteran pathogens of this serotype (serovar morrisoni) by ribotyping. The correlation of ribotype patterns with serotype suggests a clonal population structure for B. thuringiensis.
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Phenotypic comparison between rhizosphere and clinical isolates of Burkholderia cepacia
The phenotypic characteristics of four Burkholderia cepacia strains isolated from the rhizosphere and the clinical environment were compared. Tests included optimum growth temperature, utilization of carbon sources, production of HCN, indole-3-acetic acid (IAA) and siderophores, proteolytic activity, nitrogen fixation, inhibition of some phytopathogenic fungi, adherence to human mucosal and plant root epithelia, and greenhouse-based plant-growth promotion experiments using cucumber (Cucumis sativus). Results indicated that the strains of B. cepacia isolated from the rhizosphere differ markedly from their clinical counterparts. Strains isolated from the rhizosphere grew over a wider temperature range, fixed nitrogen and produced IAA, did not produce proteases, displayed a wider antibiosis against the phytopathogenic fungi studied, did not adhere to human uroepithelial cells, promoted growth of C. sativus and only produced a hydroxamate-like siderophore. In contrast, clinical isolates could not fix nitrogen or produce IAA, produced proteases, adhered to human uroepithelial cells, did not promote the growth of C. sativus and, in addition to a hydroxamate-like siderophore, produced pyochelin and salicylate siderophores. All four isolates exhibited the ability to adhere to the root tissue of C. sativus and were unable to produce HCN.
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- Genome Analysis
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Sequence and analysis of the citrulline biosynthetic operon argC–F from Bacillus subtilis
More LessThe citrulline biosynthetic operon argC–F located at 100° on the Bacillus subtilis chromosome contains seven open reading frames which encode all the enzymes required for the biosynthesis of citrulline. The operon is transcribed as a single transcription unit. The second cistron of the operon is homologous to ArgJ (ornithine acetyltransferase) from Bacillus stearothermophilus and Neisseria gonorrhoeae, suggesting that the acetylation of glutamate and the deacetylation of acetylornithine are carried out by a single enzyme in a cyclical pathway. The argF gene is an orthologue of argF from Pseudomonas aeruginosa and a paralogue of arcB from P. aeruginosa and argFlargl from Escherichia coli.
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The size of the chromosome of Azotobacter chroococcum
More LessThe DNA of Azotobacter chroococcum M4 was digested with rare-cutter restriction endonucleases Asel and Dral and restriction fragments were separated by pulsed-field gel electrophoresis. The chromosome size was estimated to be around 5300 kb by summing the sizes of the resolved restriction fragments.
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