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  • 1
    Electronic Resource
    Electronic Resource
    A kinetic model for Xylella fastidiosa adhesion, biofilm formation, and virulence (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 236 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Xylella fastidiosa is the causal agent of citrus variegated chlorosis and Pierce's disease which are the major threat to the citrus and wine industries. The most accepted hypothesis for Xf diseases affirms that it is a vascular occlusion caused by bacterial biofilm, embedded in an extracellular translucent matrix that was deduced to be the exopolysaccharide fastidian. Fourier transform infrared spectroscopy analysis demonstrated that virulent cells which form biofilm on glass have low fastidian content similar to the weak virulent ones. This indicates that high amounts of fastidian are not necessary for adhesion. In this paper we propose a kinetic model for X. fastidiosa adhesion, biofilm formation, and virulence based on electrostatic attraction between bacterial surface proteins and xylem walls. Fastidian is involved in final biofilm formation and cation sequestration in dilute sap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09663.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of no-tillage on turnover of organic matter in a Rhodic Ferralsol (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 19 (2003), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Soil organic matter (SOM) is considered to be key to sustainability of agriculture in the tropics. In southern Brazil, no-tillage has been adopted widely to control soil erosion, but its impact on the dynamics of SOM is not well established. We measured soil carbon (C) and δ13C in two crop rotations, one of which contained C4 maize (Zea mays L.), after 21 years of contrasting tillage (conventional tillage versus no-tillage). Adjacent sites that reflected historic land-uses were also sampled. In the tillage experiment there was no effect of tillage on the total amount of C in the 0–40 cm profile (even when contrasting bulk density was accounted for), and the concentration of C differed only in the 0–5 cm and 5–10 cm layers. However, the occasional input of C4 material in the maize rotation resulted in a significant effect of rotation on δ13C (P 〈0.001). Using 13C as a tracer for the SOM formed since the start of the experiment, we estimated the abundance of ‘recent’ and ‘old’ C within each depth interval. We found the main effect of tillage was to increase the medium-term turnover of SOM, particularly in the subsoil (i.e. below 20 cm depth). Compared with no-tillage, there was almost five times more recent C in the subsoil, and 20% more recent C in the 0–40 cm profile as a whole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.2003.tb00311.x
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  • 3
    Electronic Resource
    Electronic Resource
    Development of a Suitable Maintenance Diet for Anodonta cygnea (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 35 (2004), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Selenastrum, Chlorella and the Cyanophyta groups, important components of the phytoplankton in the natural habitat of Anodonta cygnea in Mira Lagoon, were used separately as experimental diet for Anodonta cygnea. To assess the effects of the different diets, several organic and inorganic compounds of the haemolymph and extrapallial fluid were measured. Protein content was significantly reduced with experimental Non Feed, and carbohydrate content with Non Feed, Selenastrum, Chlorella, and Cyanophyta diets compared to the control in the lagoon. Lipid contents in body fluids were similar among the different diet groups, with the exception of the Chlorella diet, which showed a higher value. In all diets, the inorganic elements, magnesium and chloride, presented a non-significant variation profile. The concentration of sodium and potassium was significantly affected in Selenastrum and Chlorella diets, observing in the Non Feed diet a minimum value for potassium. The non-significant variation of osmolality suggests the presence of a specific osmotic regulatory mechanism independent of the diet. A particular regulation mechanism seems to exist for both calcium and manganese ion inducing similar profiles for all experimental diets with higher contents in Selenastrum and Cyanophyta diets, respectively. The higher calcium ion concentration appears associated with lower protein-carbohydrate contents, probably due to weak calcium aggregation and deposition mechanism, except for the control and Mixture diets. In general, the concentrations of organic and inorganic compounds in the body fluids of Mixture-fed A. cygnea, were more similar to those found in the control diet group. This suggests that an equal mixture of the three algae, Selenastrum, Chlorella, and Cyanophyta, is more appropriate diet to provide the necessary nutrients for a normal maintenance of A. cygnea in the wild.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.2004.tb01074.x
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  • 4
    Electronic Resource
    Electronic Resource
    High diversity of chickpea Mesorhizobium species isolated in a Portuguese agricultural region (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 48 (2004), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Chickpea rhizobia isolated from Portuguese soils were assigned to the genus Mesorhizobium by 16S-rDNA sequencing. High species diversity was found within populations of an agricultural region in the south of Portugal. Besides the expected Mesorhizobium ciceri and M. mediterraneum, some isolates were close to M. loti or M. tianshanense and some formed a clade that may represent a new species. A new PCR-based approach, named direct amplified polymorphic DNA (DAPD) analysis, supported the 16S-based phylogeny. This suggests that this method could be used as a molecular tool to assess genetic relationships. Evaluation of genetic diversity by 16S-rDNA sequence, DAPD and protein profiles showed different levels of heterogeneity in natural populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2003.12.015
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  • 5
    Electronic Resource
    Electronic Resource
    Gene expression profile of the plant pathogen Xylella fastidiosa during biofilm formation in vitro (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 237 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A biofilm is a community of microorganisms attached to a solid surface. Cells within biofilms differ from planktonic cells, showing higher resistance to biocides, detergent, antibiotic treatments and host defense responses. Even though there are a number of gene expression studies in bacterial biofilm formation, limited information is available concerning plant pathogen. It was previously demonstrated that the plant pathogen Xylella fastidiosa could grow as a biofilm, a possibly important factor for its pathogenicity. In this study we utilized analysis of microarrays to specifically identify genes expressed in X. fastidiosa cells growing in a biofilm, when compared to planktonic cells. About half of the differentially expressed genes encode hypothetical proteins, reflecting the large number of ORFs with unknown functions in bacterial genomes. However, under the biofilm condition we observed an increase in the expression of some housekeeping genes responsible for metabolic functions. We also found a large number of genes from the pXF51 plasmid being differentially expressed. Some of the overexpressed genes in the biofilm condition encode proteins involved in attachment to surfaces. Other genes possibly confer advantages to the bacterium in the environment that it colonizes. This study demonstrates that the gene expression in the biofilm growth condition of the plant pathogen X. fastidiosa is quite similar to other characterized systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09716.x
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  • 6
    Electronic Resource
    Electronic Resource
    Competitive hybridization on spotted microarrays as a tool to conduct comparative genomic analyses of Xylella fastidiosa strains (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 216 (2002), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Xylella fastidiosa strains are responsible for several plant diseases and since such isolates display a broad host range and complex biological behavior, genomic comparisons employing microarray hybridizations may provide an effective method to compare them. Thus, we performed a thorough validation of this type of approach using two recently sequenced strains of this phytopathogen. By matching microarray hybridization results to direct sequence comparisons, we were able to establish precise cutoff ratios for common and exclusive sequences, allowing the identification of exclusive genes involved in important biological traits. This validation will enable the use of microarray-based comparisons across a wide variety of microorganisms
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2002.tb11408.x
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  • 7
    Electronic Resource
    Electronic Resource
    Distribution of papG alleles among uropathogenic Escherichia coli isolated from different species (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 202 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The distribution of alleles I, II and III of the P adhesin gene papG among Escherichia coli isolated from urinary tract infections in humans, dogs and cats was studied by PCR. Allele I was present in 6% and 5% of the human and cat isolates. Allele II as such was present in 30% and 22%, or in association with allele III in 12% and 2% of the human and canine isolates, respectively. Allele III was present in 33% of the human strains and predominated largely over allele II in E. coli isolates from cystitis of animal origin (72% in dog and 95% in cat strains). The three different classes of the PapG adhesin have been suggested to play a role in host specificity, for example human versus canine specificity. Recent studies, however, showed papG III positive human and dog cystitis isolates to be largely indistinguishable. We found the Class II allele in animal isolates and detected for the first time in Europe the Class I allele in a different genetic background than the J96-like clonal group. Our findings show that uropathogenic E. coli isolates from different species can have the same papG alleles and thus may have zoonotic potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10804.x
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  • 8
    Electronic Resource
    Electronic Resource
    Potential roles for the glnB and ntrYX genes in Azospirillum brasilense (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 201 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three Azospirillum brasilense mutants constitutive for nitrogen fixation (NifC) in the presence of NH4+ and deficient in nitrate-dependent growth were used as tools to define the roles of the glnB and ntrYX genes in this organism. Mutant HM14 was complemented for nitrate-dependent growth and NH4+ regulation of nitrogenase by plasmid pL46 which contains the ntrYX genes of A. brasilense. Mutant HM26 was restored for NH4+ regulation and nitrate-dependent growth by plasmid pJC1, carrying the A. brasilense glnB gene expressed from a constitutive promoter. Mutant HM053, on the other hand, was not complemented for NH4+ regulation of nitrogenase and nitrate-dependent growth by both plasmids pJCI and pL46. The levels and control of glutamine synthetase activity of all mutants were not affected by both plasmids pL46 (ntrYX) and pJC1 (glnB). These results support the characterization of strains HM14 as an ntrYX mutant and strain HM26 as a glnB mutant and the involvement of ntrYX and glnB in the regulation of the general nitrogen metabolism in A. brasilense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10757.x
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  • 9
    Electronic Resource
    Electronic Resource
    Impact of oil contamination and biostimulation on the diversity of indigenous bacterial communities in soil microcosms (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 49 (2004), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The aim of this study was to analyse the effect of oil contamination and biostimulation (soil pH raise, and nitrogen, phosphate and sulphur addition) on the diversity of a bacterial community of an acidic Cambisol under Atlantic Forest. The experiment was based on the enumeration of bacterial populations and hydrocarbon degraders in microcosms through the use of conventional plating techniques and molecular fingerprinting of samples directly from the environment. PCR followed by denaturing gradient gel electrophoresis (DGGE) was used to generate microbial community fingerprints employing 16S rRNA gene as molecular marker. Biostimulation led to increases of soil pH (to 7.0) and of the levels of phosphorus and K, Ca, and Mg. Oil contamination caused an increase in soil organic carbon (170–190% higher than control soil). Total bacterial counts were stable throughout the experiment, while MPN counts of hydrocarbon degraders showed an increase in the biostimulated and oil-contaminated soil samples. Molecular fingerprinting performed with 16S rRNA gene PCR and DGGE analysis revealed stable patterns along the 360 days of experiment, showing little change in oil-contaminated microcosms after 90 days. The DGGE patterns of the biostimulated samples showed severe changes due to decreases in the number of bands as compared to the control samples as from 15 days after addition of nutrients to the soil. Results obtained in the present study indicate that the addition of inorganic compounds to soil in conjunction with oil contamination has a greater impact on the bacterial community than oil contamination only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsec.2004.04.007
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