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Martin Hartmann

Publications and source records attributed to Martin Hartmann.

18 recordsLinked to original sources
PubMed2007

Residual polymerase activity-induced bias in terminal restriction fragment length polymorphism analysis.

Residual activity of polymerase chain reaction DNA polymerases in restriction analyses strongly affected genetic profiling based on terminal restriction fragment length polymorphisms. Artificial fragment sizes produced as a result of 5'-overhang restriction site fill-in and addition of a terminal A may bias genetic profiling and genotyping of microbial communities. Efficient removal of polymerases retained original fragment sizes and significantly reduced this profiling bias in soil bacterial communities.

Bacteria↗
PubMed2006

Community structure analyses are more sensitive to differences in soil bacterial communities than anonymous diversity indices.

Changes in the diversity and structure of soil microbial communities may offer a key to understanding the impact of environmental factors on soil quality in agriculturally managed systems. Twenty-five years of biodynamic, bio-organic, or conventional management in the DOK long-term experiment in Switzerland significantly altered soil bacterial community structures, as assessed by terminal restriction fragment length polymorphism (T-RFLP) analysis. To evaluate these results, the relation between bacterial diversity and bacterial community structures and their discrimination potential were investigated by sequence and T-RFLP analyses of 1,904 bacterial 16S rRNA gene clones derived from the DOK soils. Standard anonymous diversity indices such as Shannon, Chao1, and ACE or rarefaction analysis did not allow detection of management-dependent influences on the soil bacterial community. Bacterial community structures determined by sequence and T-RFLP analyses of the three gene libraries substantiated changes previously observed by soil bacterial community level T-RFLP profiling. This supported the value of high-throughput monitoring tools such as T-RFLP analysis for assessment of differences in soil microbial communities. The gene library approach also allowed identification of potential management-specific indicator taxa, which were derived from nine different bacterial phyla. These results clearly demonstrate the advantages of community structure analyses over those based on anonymous diversity indices when analyzing complex soil microbial communities.

Agriculture↗
PubMed2006

A novel strategy to extract specific phylogenetic sequence information from community T-RFLP.

Cultivation-independent analyses of soil microbial community structures are frequently used to describe microbiological soil characteristics. Semi-automated terminal restriction fragment length polymorphism (T-RFLP) analyses yield high-resolution genetic profiles of highly diverse soil microbial communities and hold great potential for use in routine soil quality monitoring. A serious limitation of T-RFLP analyses has been the inability to reliably affiliate observed terminal restriction fragments (T-RF) to phylogenetic groups. In the study presented here, we were able to overcome this limitation of T-RFLP. With a combination of adapter ligation, fragment size selection, and re-amplification with adapter site specific PCR, we were able to isolate a T-RF-fraction of a narrow size-range containing a T-RF that was significantly more abundant in heavy metal amended soils. Cloning the size-selected T-RF fraction allowed for the efficient isolation of clones containing this specific T-RF. Sequence determination and phylogenetic inference in RDP-II affiliated the sequence to unclassified cyanobacteria. Specific primer design and PCR amplification from bulk soil DNA allowed for independent confirmation of the results from bacterial T-RFLP and T-RF cloning. Our results show that specific T-RFs can be efficiently isolated and identified, and that the adapter ligation approach holds great potential for genetic profiling and for identification of community components of interest.

Base Sequence↗
PubMed2006

Dielectric spectroscopy of nano BaTiO3 confined in MCM-41 mesoporous molecular sieve materials.

Dielectric properties of barium titanate (BaTiO3) particles, synthesized directly in the pores of MCM-41 materials, have been investigated in the frequency range from 20 Hz to 1 MHz for temperature intervals from 100 K to 500 K. The dielectric spectra of BaTiO3 confined in these molecular sieves were compared with the results obtained from the investigation of pure MCM-41 materials. Obtained results confirmed successful incorporation of BaTiO3 into porous matrix, but no phase transition from paraelectric to ferroelectric phase was observed due to the particle size being smaller than the critical size. Also, the overall dielectric response of investigated materials is strongly influenced by adsorbed water molecules.

Barium Compounds↗
PubMed2006

Ranking the magnitude of crop and farming system effects on soil microbial biomass and genetic structure of bacterial communities.

Biological soil characteristics such as microbial biomass, community structures, activities, and functions may provide important information on environmental and anthropogenic influences on agricultural soils. Diagnostic tools and detailed statistical approaches need to be developed for a reliable evaluation of these parameters, in order to allow classification and quantification of the magnitude of such effects. The DOK long-term agricultural field experiment was initiated in 1978 in Switzerland for the evaluation of organic and conventional farming practices. It includes three representative Swiss farming systems with biodynamic, bio-organic and conventional fertilization and plant protection schemes along with minerally fertilized and unfertilized controls. Effects on microbial soil characteristics induced by the long-term management at two different stages in the crop rotation, i.e. winter wheat after potato or corn, were investigated by analyzing soil bacterial community structures using analysis of PCR-amplified rRNA genes by terminal restriction fragment length polymorphism and ribosomal intergenic spacer analysis. Application of farmyard manure consistently revealed the strongest influence on bacterial community structures and biomass contents. Effects of management and plant protection regimes occurred on an intermediate level, while the two stages in the crop rotation had a marginal influence that was not significant.

Agriculture↗
PubMed2006

Bacterial community structure and activity in different Cd-treated forest soils.

In this study we compared indicators of Cd bioavailability (water extracts, Lakanen extracts, free ions) and ecotoxicity in forest soils with contrasting physico-chemical characteristics. Soil samples were treated with CdCl(2) solutions (0, 0.1, 1, 10 and 100 mM) and incubated for 30 days. Microbial activity indexes (acid phosphatase, beta-glucosidase, basal respiration) and changes in bacterial community structure using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting were investigated. The Cd concentrations measured ranged from 1% to 37% of the total additions in water extracts, to higher levels in Lakanen extracts. Effects of Cd were observed at bioavailable concentrations exceeding United Nations/European Economic Commission UN/ECE guidelines for total Cd in the soil solution. Basal respiration was the most affected index, while enzymatic activities showed variable responses to the Cd treatments. We also noticed that soils with pH higher than 6.7 and clay content higher than 50% showed inhibition of basal respiration but no marked shift in bacterial community structure. Soils with lower pH (pH <5.8) with less clay content (<50%) showed in addition strong changes in the bacterial community structure. Our results provide evidence for the importance of relating the effects of Cd on the soil communities to soil properties and to bioavailability.

Acid Phosphatase↗
PubMed2005

Critical assessment of electron spin resonance studies on Cu(I)-NO complexes in Cu-ZSM-5 zeolites prepared by solid- and liquid-state ion exchange.

Cu(I)-NO adsorption complexes were formed over Cu-ZSM-5 zeolites prepared by (i) solid-state ion exchange of NH(4)-ZSM-5 with CuCl and (ii) liquid-state ion exchange of ZSM-5 with Cu(CH(3)COO)(2). Electron spin resonance spectroscopy revealed the formation of two different Cu(I)-NO species A and B in both systems, whose spin Hamiltonian parameters are comparable with those already reported for the Cu(I)-NO species formed over 66% Cu(II) liquid-state ion-exchanged Cu-ZSM-5 materials. The population of the species A and B differs for the two systems studied. Formation of species B is more favored in the solid-state ion-exchanged Cu-ZSM-5 when compared to the liquid-state exchanged zeolite. The X-, Q- and W-band electron spin resonance spectra recorded at 6 and 77 K reveal the presence of a rigid geometry of the adsorption complexes at 6 K and a dynamic complex structure at higher temperatures such as 77 K. This is indicated by the change in the spin Hamiltonian parameters of the formed Cu(I)-NO species in both the liquid- and solid-state ion-exchanged Cu-ZSM-5 zeolites from 6 to 77 K. Possible models for the motional effects found at elevated temperatures are discussed. The temperature dependence of the electron spin phase memory time measured by two-pulse electron spin-echo experiments indicates, likewise, the onset of a motional process of the adsorbed NO molecules at temperatures above 10 K. The studies support previous assignments where the NO complexes are formed at two different Cu(I) cationic sites in the ZSM-5 framework and highlight that multifrequency electron spin resonance experiments at low temperatures are essential for reliable determination of the spin Hamiltonian parameters of the formed adsorption complexes for further comparison with Cu(I)-NO complex structures predicted by quantum chemical calculations.

Journal Article↗
PubMed2005

Pulsed ENDOR study of Cu(I)-NO adsorption complexes in Cu-L zeolite.

The local environments of Cu(I)-NO adsorption complexes formed in zeolites Cu-L and Cu-ZSM-5 were studied by electron spin resonance (ESR), pulsed electron nuclear double resonance (ENDOR), and hyperfine sublevel correlation spectroscopy (HYSCORE). Cu(I)-NO complexes have attracted special interest because they are important intermediates in the catalytic decomposition of nitric oxide over copper exchanged zeolites. Recently, detailed structures of the complexes in Cu-ZSM-5 zeolites, O2-Al-O2-Cu(I)-NO, have been proposed on the basis of quantum chemical calculations (Pietrzyk, et al. J. Phys. Chem. B 2003, 107, 6105. Dedecek, et al. Phys. Chem. Chem. Phys. 2002, 4, 5406). 27Al pulsed ENDOR and HYSCORE experiments allowed the hyperfine coupling parameters of an aluminum nuclei found in the vicinity of the Cu(I)-NO complex formed in zeolite Cu-L to be estimated. The data indicate that the aluminum atom is located in the third coordination sphere of the adsorbed NO molecule in agreement with the suggested geometry of the adsorption sites. Broad distributions of aluminum nuclear quadrupole and hyperfine coupling parameters and short electron spin relaxation times of the Cu(I)-NO species prevented the determination of the 27Al hyperfine couplings for zeolite Cu-ZSM-5.

Journal Article↗
PubMed2005

EPR spectroscopy of Cu(I)-NO adsorption complexes formed over Cu-ZSM-5 and Cu-MCM-22 zeolites.

The Cu(I)-NO adsorption complexes were formed over copper exchanged and autoreduced high siliceous Cu-ZSM-5 and Cu-MCM-22 zeolites and studied by EPR spectroscopy at X-, Q-, and W-band frequencies. The spin Hamiltonian parameters of the Cu(I)-NO species are indicative of a nitrogen-centered radical complex with a bent geometry and a significant contribution of the Cu(I) 4s atomic orbital to the wave function of the unpaired electron. Two different Cu(I)-NO species were found in both zeolites. It has been confirmed by comparing the experimental data with the results of previous theoretical studies that the presence of two different species is due to the formation of Cu(I)-NO adsorption complexes from two different Cu(I) sites in the zeolite matrix with different numbers of oxygen coligands. The structure of the two sites in the Cu-ZSM-5 and Cu-MCM-22 zeolites must be similar as the spin Hamiltonian parameters are found to be almost independent of the zeolite matrix, where the Cu(I)-NO complex is formed. The EPR signal intensity of the Cu(I)-NO species was studied as a function of the NO loading, and the formation of diamagnetic Cu(I)-(NO)(2) species with rising NO pressure at the expense of paramagnetic Cu(I)-NO monomers could be demonstrated for both systems at low temperatures.

Adsorption↗
PubMed2005

Semi-automated genetic analyses of soil microbial communities: comparison of T-RFLP and RISA based on descriptive and discriminative statistical approaches.

Cultivation independent analyses of soil microbial community structures are frequently used to describe microbiological soil characteristics. This approach is based on direct extraction of total soil DNA followed by PCR amplification of selected marker genes and subsequent genetic fingerprint analyses. Semi-automated genetic fingerprinting techniques such as terminal restriction fragment length polymorphism (T-RFLP) and ribosomal intergenic spacer analysis (RISA) yield high-resolution patterns of highly diverse soil microbial communities and hold great potential for use in routine soil quality monitoring, when rapid high throughput screening for differences or changes is more important than phylogenetic identification of organisms affected. Our objective was to perform profound statistical analysis to evaluate the cultivation independent approach and the consistency of results from T-RFLP and RISA. As a model system, we used two different heavy metal treated soils from an open top chamber experiment. Bacterial T-RFLP and RISA profiles of 16S rDNA were converted into numeric data matrices in order to allow for detailed statistical analyses with cluster analysis, Mantel test statistics, Monte Carlo permutation tests and ANOVA. Analyses revealed that soil DNA-contents were significantly correlated with soil microbial biomass in our system. T-RFLP and RISA yielded highly consistent and correlating results and both allowed to distinguish the four treatments with equal significance. While RISA represents a fast and general fingerprinting method of moderate cost and labor intensity, T-RFLP is technically more demanding but offers the advantage of phylogenetic identification of detected soil microorganisms. Therefore, selection of either of these methods should be based on the specific research question under investigation.

Bacteria↗
PubMed2005

[Treatment of erysipelas in Germany and Austria--results of a survey in German and Austrian dermatological clinics].

BACKGROUND: Erysipelas is a severe soft tissue infection usually caused by streptococci. The infection is restricted to the dermis and subcutaneous tissues. Treatment with antibiotics is essential. Many different therapeutic regimens are recommended, based mainly on empirical data and only partly proven by clinical studies. MATERIAL AND METHODS: Our aim was to evaluate the treatment of erysipelas in Germany and Austria by means of a questionnaire and to derive treatment recommendations from this data. RESULTS AND CONCLUSION: The majority of clinics treat patients with erysipelas as inpatients with intravenous antibiotics. The usual first line treatment is group G penicillin (80%). Other choices include amino-penicillins (11%), cephalosporins (16.5%) and anti-staphylococcal penicillins (6.9%) are used. As second line antibiotics macrolides (63.5%), clindamycin (52.5%), penicillins (18.5%), cephalosporins (40%) and fluoroquinolones (20.5%) are mentioned. Carbapenems, tetracyclines, nitroimidazoles, glycopeptides, aminoglycosides, cotrimoxazole, fusidic acid and fosfomycin are used rarely. The median treatment duration is 10 days. Adjuvant measures are anticoagulation, non-steroidal anti-inflammatory agents, dressings, immobilization and treatment of local predisposing factors such as interdigital tinea.

Ambulatory Care Facilities↗
PubMed2005

Comparison of efavirenz and nevirapine in HIV-infected patients (NEEF Cohort).

The non-nucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz (EFV) and nevirapine (NVP) taken in combination with nucleoside reverse transcriptase inhibitors (NRTIs) have both shown to be just as highly effective as protease inhibitors (PIs) in reducing viral load in patients infected with HIV. Our study compares the performance of these two NNRTIs with each other. This was a non-randomized, prospective, two-arm, multi-centre trial. We evaluated all patients with an EFV- or NVP-containing antiretroviral regimen. The primary endpoint was the difference in success rates defined as a viral load of </=50 copies/mL at week 48. chi(2)-tests were used for naïve and pretreated patients using intention-to-treat (ITT) and on-treatment analysis. As secondary endpoints, a viral load of </=500 copies/mL and CD4 count at week 48 for naïve patients were evaluated. A Cox regression was used to adjust for prespecified covariates. We included 662 patients (NVP 337, EFV 325). The difference in success rates in the ITT analysis was 4.5% ( -11.5%, 19.0%), P=0.578. Pretreated patients with a triple therapy show a difference of 10.1 (-0.3, 20.6), P=0.056. Non-significant results appeared for all secondary analyses. In this trial, no difference between EFV and NVP in combination with NRTI backbone therapy can be shown, regarding viral load. Further randomized studies are necessary to evaluate possible differences.

Alkynes↗
PubMed2002

Direct synthesis and catalytic evaluation of AlSBA-1.

The direct synthesis of the new mesoporous molecular sieve AlSBA-1 containing exclusively tetrahedrally coordinated aluminium and the catalytic activity of the novel material in the isomerization of n-decane are reported.

Journal Article↗
PubMed2002

Time-resolved 1H and 13C NMR spectroscopy for detailed analyses of the Azotobacter vinelandii mannuronan C-5 epimerase reaction.

AlgE2, AlgE4, and AlgE6 are members of a family of mannuronan C-5 epimerases encoded by Azotobacter vinelandii, and are active in the biosynthesis of alginate, where they catalyze the post-polymerization conversion of beta-D-mannuronic acid residues into alpha-L-guluronic acid residues. To study the kinetics and mode of action of these enzymes, homopolymeric mannuronan and other alginate samples with various composition were epimerized by letting the enzymatic reaction take place in an NMR tube. Series of 1H NMR spectra were recorded to obtain a time-resolved picture of the epimerization progress and the formation of specific monomer sequences. Starting from mannuronan, guluronic acid contents of up to 82% were introduced by the enzymes, and the product specificity, substrate selectivity, and reaction rates have been investigated. To obtain direct information of the GulA-block formation, similar experiments were performed using a 13C-1-enriched mannuronan as substrate. The NMR results were found to be in good agreement with data obtained by a radioisotope assay based on 3H-5-labeled substrates.

Alginates↗
PubMed2002

Mode of action of recombinant Azotobacter vinelandii mannuronan C-5 epimerases AlgE2 and AlgE4.

The enzymes mannuronan C-5 epimerases catalyze conversion of beta-D-mannuronic acid to alpha-L-guluronic acid in alginates at the polymer level and thereby introduce sequences that have functional properties relevant to gelation. The enzymatic conversion by recombinant mannuronan C-5 epimerases AlgE4 and AlgE2 on alginate type substrates with different degree of polymerization and initial low fraction of alpha-L-guluronic acid was investigated. Essentially no enzymatic activity was found for fractionated mannuronan oligomer substrates with an average degree of polymerization, DP(n), less than or equal 6, whereas increasing the DP(n) yielded increased epimerization activity. This indicates that these enzymes have an active site consisting of binding domains for consecutive residues that requires interaction with 7 or more consecutive residues to show enzymatic activity. The experimentally determined kinetics of the reaction, and the residue sequence arrangement introduced by the epimerization, were modeled using Monte Carlo simulation accounting for the various competing intrachain substrates and assuming either a processive mode of action or preferred attack. The comparison between experimental data and simulation results suggests that epimerization by AlgE4 is best described by a processive mode of action, whereas the mode of action of AlgE2 appears to be more difficult to determine.

Alginates↗
PubMed2002

Patch tests with thiurams at 0.25% pet. and 1% pet. are of equal diagnostic value.

Thiuram mix is tested in the standard series at a test concentration of 1% pet. The single thiurams (DPTD, TMTD, TMTM, TETD), however, are usually tested at 0.25% pet. in Germany. In other countries, the individual components of thiuram mix are tested at 1% pet. The German Contact Dermatitis Research Group (DKG) compared both patch test concentrations in 530 patients in order to find out if (i) a significant number of positive patch tests are missed by testing at the lower concentration, (ii) problems with irritant test reactions occur by increasing the test concentration to 1%, and (iii) the sensitivity of the thiuram mix rises when the breakdown test is done with the higher concentration. Slightly more positive reactions were seen with the higher concentration, but this increase did not reach statistical significance. The reaction index, as a measure for the relation of positive to irritant and/or questionable reactions, remained unchanged for the individual thiurams. The sensitivity of the mix also did not change when the breakdown test was performed with 1% pet. instead of 0.25% pet. Thus, we conclude that both concentrations are of equal diagnostic value in patch testing.

Dermatitis, Allergic Contact↗