Gerhard Welzl - Academia.edu (original) (raw)

Papers by Gerhard Welzl

Zeitschrift fur Naturforschung C

Analyses of different plant stressors are often based on gene expression studies. Quantitative re... more Analyses of different plant stressors are often based on gene expression studies. Quantitative real-time RT-PCR (qRT-PCR) is the most sensitive method for the detection of low abundance transcripts. However, a critical point to note is the selection of housekeeping genes as an internal control. Many so-called 'housekeeping genes' are often affected by different stress factors and may not be suitable for use as an internal reference. We tested six housekeeping genes of European beech by qRT-PCR using the Sybr Green PCR kit. Specific primers were designed for 18S rRNA, actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH1, GAPDH2), α-tubulin, and ubiquitin-like protein. Beech saplings were treated with increased concentrations of either ozone or CO 2 . In parallel, the expression of these genes was analyzed upon pathogen infection with Phytophthora citricola. To test the applicability of these genes as internal controls under realistic outdoor conditions, sun and shade leaves of 60-year-old trees were used for comparison. The regulation of all genes was tested using a linear mixed-effect model of the R-system. Results from independent experiments showed that the only gene not affected by any treatment was actin. The expression of the other housekeeping genes varied more or less with the degree of stress applied. These results highlight the importance of undergoing an individual selection of internal control genes for different experimental conditions.

Umweltwissenschaften und Schadstoff-Forschung

Herbicides are structurally diverse chemicals that inhibit plant-specific targets, however their ... more Herbicides are structurally diverse chemicals that inhibit plant-specific targets, however their off-target and potentially differentiating side-effects are less well defined. In this study, genome-wide expression profiling based on Affymetrix AtH1 arrays was used to identify discriminating responses of Arabidopsis thaliana to five related chemicals that target two different branches of amino acid biosynthesis. The compounds included glyphosate that targets 5-enolpyruvylshikimate-3-phosphate synthase and four diverse acetolactate synthase (ALS) inhibiting compounds. The ALS inhibitors comprised three different chemical classes as well as two compounds based on the same, sulfonylurea backbone. In contrast to glyphosate, which affected only a few transcripts, ALS inhibitors led to numerous transcriptional changes which indicated off-target effects related to C-metabolism, secondary metabolism, cell wall modification and growth. The expression pattern of a set of 101 genes provided a s...

Applied Soil Ecology, 2015

ABSTRACT Application of manure for soil fertilization is a common practice in arable and pasture ... more ABSTRACT Application of manure for soil fertilization is a common practice in arable and pasture soils. As antibiotics are regularly used in animal husbandry, these compounds often enter the soil via manure application. The effects of antibiotics on microbial communities, however, might depend on soil moisture, as water availability may influence both the fate of the compound and the activity of the microbes. To test this hypothesis, we investigated the effects of the application of manure containing the antibiotic sulfadiazine (SDZ) on the abundance and activity of nitrifies and denitrifies in soil, based on the copy number of marker genes and their related potential activities, as affected by different moisture regimes. We observed significant effects of SDZ on potential denitrification activity, but those were not influenced by the soil moisture regime. Nevertheless, neither SDZ nor changes on moisture significantly affected the abundance of denitrifies. In contrast, both potential nitrification activity and abundance of ammonia oxidizing bacteria were significantly affected by the application of manure containing SDZ and moisture regime. Interestingly, no effects were observed for ammonia oxidizing archaea. Overall, our data show that soil moisture modulates the effects of antibiotics in soil microbial communities, and we recommend to include this parameter in the risk assessment of new chemicals.

Our data demonstrated: (i) a clear transcriptional ozone response of juvenile beech. (ii) Althoug... more Our data demonstrated: (i) a clear transcriptional ozone response of juvenile beech. (ii) Although the expression profile was not identical in both years, a common tendency of gene expression was obvious. The more pronounced changes in 2006 may be explained by a higher stomatal conductance in 2006 compared to 2005. (iii) (iv) First proteome analyses also indicated an ozone response of beech leaves.

Umweltwissenschaften und Schadstoff-Forschung, 2002

... Multikriterielle Bewertungs-und Entscheidungshilfe-Instrumente Stefan Pudenz 1, Rainer Briigg... more ... Multikriterielle Bewertungs-und Entscheidungshilfe-Instrumente Stefan Pudenz 1, Rainer Briiggemann 2, Kristina Voigt 3 und Gerhard Welzl 3 ... Match 42, 7-21 [16] Randic M, Vracko M, Novic M, Basak SC (2000): On ordering of folded structures. ...

Umweltwissenschaften und Schadstoff-Forschung, 2002

Zusammenfassung Ziel und Hintergrund Umweltmonitoring-Informationen über einige Luftschadstoffe ... more Zusammenfassung Ziel und Hintergrund Umweltmonitoring-Informationen über einige Luftschadstoffe wie Ozon (O3), Stickstoffdioxid (NO2), Stickstoffmonoxid (NO), Kohlendioxid (CO2) und Kohlenmonoxid (CO), zuweilen auch Schwebstaub, Benzol und andere Umweltchemikalien stehen der Öffentlichkeit im Internet zur freien Verfügung. Da fast alle Bundesländer bzw. Städte unterschiedliche Informationssysteme etabliert haben, ist eine Gegenüberstellung der Systeme mit deren Vor- und Nachteilen von großem Interesse. Schwerpunkte Es werden Umweltmonitoring-Informationssysteme

Zeitschrift für Naturforschung. C, Journal of biosciences

Analyses of different plant stressors are often based on gene expression studies. Quantitative re... more Analyses of different plant stressors are often based on gene expression studies. Quantitative real-time RT-PCR (qRT-PCR) is the most sensitive method for the detection of low abundance transcripts. However, a critical point to note is the selection of housekeeping genes as an internal control. Many so-called 'housekeeping genes' are often affected by different stress factors and may not be suitable for use as an internal reference. We tested six housekeeping genes of European beech by qRT-PCR using the Sybr Green PCR kit. Specific primers were designed for 18S rRNA, actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH1, GAPDH2), a-tubulin, and ubiquitin-like protein. Beech saplings were treated with increased concentrations of either ozone or CO2. In parallel, the expression of these genes was analyzed upon pathogen infection with Phytophthora citricola. To test the applicability of these genes as internal controls under realistic outdoor conditions, sun and shade leaves ...

Soil Biology and Biochemistry, 2011

Effects of decomposers on plant growth are generally ascribed to nutrient mobilization. However, ... more Effects of decomposers on plant growth are generally ascribed to nutrient mobilization. However, Collembola, which are ubiquitous and abundant decomposers in soil, are known to alter root morphology with, in some cases, the nutrient content of plants remaining unaffected. We studied the interaction of Collembola (Protaphorura fimata) with the model plant Arabidopsis thaliana in order to link phenotypic responses of A. thaliana to decomposers using changes in gene expression. Collembola reduced the growth of A. thaliana during early growth stages, but this decrease was compensated later. Expression analyses revealed striking differences in the response of plant roots and shoots three and six days after exposure of Arabidopsis to Collembola. Among the specifically affected transcripts in roots, the induction of auxin-responsive genes was significantly increased after six days, suggesting that P. fimata provoked auxin-related signalling in roots. In shoots, transcriptional changes were more diverse and functional categories involved in defence and metabolic re-arrangements were significantly affected. These responses might have been related to the transitory reduction in growth which presumably was caused by Collembola feeding on and/or damaging roots. The results suggest that Collembola may improve plant resistance against the attack by herbivores by stimulating the production of secondary compounds while concomitantly compensating the costs of producing them by fostering root growth and nutrient exploitation.

The Science of the total environment, Jan 15, 2010

A soil-borne microbial community isolated from a contaminated site was previously shown to minera... more A soil-borne microbial community isolated from a contaminated site was previously shown to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB) under aerobic conditions. The key degrader in this community was identified as Bordetella sp. F2. The objective of the study was to test the capacity of the microbial community to degrade a complex mixture of 27 organochlorine compounds and pesticides (OCPs) commonly detected in the environment. The hypothesis was that the microbes would utilize the OCPs as carbon sources at the low concentrations of these compounds, found in natural waters and soil solution. The study was carried out in liquid culture and the changes in concentration of the OCPs were monitored using GC-MS. Data analysis was done using a multivariate analysis method similar to Principal Response Curve (PRC) analysis. Contrary to expectations, the data analysis showed a general trend where higher concentrations were observed in the microbially treated samples relative to the control...

Acta hydrochimica et hydrobiologica, 2005

ABSTRACT

Plant secondary metabolism significantly contributes to defensive measures against adverse abioti... more Plant secondary metabolism significantly contributes to defensive measures against adverse abiotic and biotic cues. To investigate stress-induced, transcriptional alterations of underlying effector gene families, which encode enzymes acting consecutively in secondary metabolism and defense reactions, a DNA array (MetArray) harboring gene-specific probes was established. It comprised complete sets of genes encoding 109 secondary product glycosyltransferases and 63 glutathione-utilizing enzymes along

Trees, 2009

The shikimate pathway plays a central role in the formation of aromatic intermediates in the prod... more The shikimate pathway plays a central role in the formation of aromatic intermediates in the production of stilbenes, flavonoids and lignins. Ozone effects on the levels of transcripts in this pathway were studied in saplings of European beech. Complementary DNA (cDNA) clones of all genes of this pathway were isolated, and quantitative real-time RT-PCR (qRT-PCR) using RNA isolated from leaves of ozone-treated saplings showed a strong induction of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase 1 (DAHPS1), DAHPS3, 3-dehydroquinate dehydratase/ shikimate dehydrogenase (DHQD/SD), 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), and chorismate mutase (CM) transcripts. In contrast, DAHPS2, 3-dehydroquinate synthase (DHQS), shikimate kinase (SK), and chorismate synthase (CS) transcripts were only weakly induced. Earliest induction could be observed after 2 days of ozone treatment for DAHPS1, SK, EPSPS and CM. The coordinated regulation was evident for 3-5 weeks after the onset of ozone fumigation, and increased transcript levels were still detectable after another 7 weeks. Western blot analyses of DAHPS3 and DHQD/SD showed an increased protein level in agreement with the increased transcription levels. Ozone-dependent leaf lesions appeared 7 weeks after onset of ozone exposure. Strongly elevated were levels of conjugates of salicylic (SA) and gentisic acids (GA), either derived directly from chorismate, the key product of the shikimate pathway, or via phenylalanine, cinnamic, and benzoic acids. Concentrations of cell wall-bound phenolic compounds increased in both control and ozone-treated saplings with the latter showing slightly higher levels. Interestingly, however, this increase of cell wall-bound phenolics was accompanied by a decrease of soluble phenolics, which may indicate their deposition into the cell wall.

Toxicology Mechanisms and Methods, 2004

Alongside food, emissions from amalgam fillings are an essential contribution to man&... more Alongside food, emissions from amalgam fillings are an essential contribution to man's mercury burden. Previous methods for the determination of intraoral mercury vapor (Hg degrees ) release used principally some form of preconcentration of Hg on gold (film or wool), allowing relatively few measurements with unknown precision and sensitivity at selected times. Recently available computer-controlled Hg detectors operating on Zeeman atomic absorption spectroscopy (ZAAS) facilitate the direct real-time measurement of Hg degrees concentrations. It was the aim to adapt this method for a comparative investigation of emission processes from fillings in situ and from amalgam specimens in vitro. In addition to the ZAAS instrument, the apparatus consisted of a pump, magnetic valves, an electronic flow controller and a handle with a disposable mouth piece for aspiration of oral air. A programmable timer integrated the computer-controlled instrument operation and the data collection into a standard sampling protocol. A fast exponential decay of the emission was found after stimulation of amalgam specimens and of fillings in situ (halftimes 8.6 and 10.7 min). Precision was evaluated by a series of measurements on a single patient which indicated a consistently low coefficient of variation between 18% and 25%. After insertion of a few new fillings, sensitivity was high enough to detect a significant increase in emission against the background emission from the majority of old fillings. Zeeman-AAS in connection with a semi-automated sampling protocol and data storage provides precise in-situ measurements of Hg degrees emission from dental amalgam with real-time resolution. This facilitates the detailed exploration of the Hg degrees release kinetics and the applicability to large-scale studies.

The ISME Journal, 2012

Alkanes are major constituents of plant-derived waxy materials. In this study, we investigated th... more Alkanes are major constituents of plant-derived waxy materials. In this study, we investigated the abundance, community structure and activity of bacteria harbouring the alkane monooxygenase gene alkB, which catalyses a major step in the pathway of aerobic alkane degradation in the litter layer, the litter-soil interface and in bulk soil at three time points during the degradation of maize and pea plant litter (2, 8 and 30 weeks) to improve our understanding about drivers for microbial performance in different soil compartments. Soil cores of different soil textures (sandy and silty) were taken from an agricultural field and incubated at constant laboratory conditions. The abundance of alkB genes and transcripts (by qPCR) as well as the community structure (by terminal restriction fragment polymorphism fingerprinting) were measured in combination with the concentrations and composition of alkanes. The results obtained indicate a clear response pattern of all investigated biotic and abiotic parameters depending on the applied litter material, the type of soil used, the time point of sampling and the soil compartment studied. As expected the distribution of alkanes of different chain length formed a steep gradient from the litter layer to the bulk soil. Mainly in the two upper soil compartments community structure and abundance patterns of alkB were driven by the applied litter type and its degradation. Surprisingly, the differences between the compartments in one soil were more pronounced than the differences between similar compartments in the two soils studied. This indicates the necessity for analysing processes in different soil compartments to improve our mechanistic understanding of the dynamics of distinct functional groups of microbes.

Soil Biology and Biochemistry, 2014

ABSTRACT Spatial and temporal dynamics of microbial community structure and function in subsoils ... more ABSTRACT Spatial and temporal dynamics of microbial community structure and function in subsoils have been rarely studied in the past. In this paper we present data on how bacterial communities as well as selected functional groups of microbes change in the rhizosphere, the drilosphere, and in bulk soil over time in topsoil as well as in subsoil. We show that the overall richness of bacteria and abundance of nitrifiers and denitrifiers decreases in bulk soil with soil depth. However, these effects were not or to a much lower degree observed in the rhizosphere and the drilosphere. Temporal fluctuations contributed by far less than spatial factors to the dynamics of bacterial communities and abundance of nitrifiers and denitrifiers in all compartments independent from the soil depth.

Soil Biology and Biochemistry, 2014

In this study, drivers for ammonia-oxidation and the related microbial communities (ammonia-oxidi... more In this study, drivers for ammonia-oxidation and the related microbial communities (ammonia-oxidizing bacteria and archaea) were investigated in grassland soils on the local as well as on the regional scale focusing on the role of land-use intensity (LUI). To this end, 150 sites from three distinct regions across Germany were selected, covering the whole range of LUI levels (from natural grasslands up to intensive managed meadows). Furthermore, the role of contrasting soil types was analyzed in one of the regions (high vs low organic matter content) for ammonia-oxidation. We revealed a significant increase in potential nitrification rates and abundance of ammonia-oxidizing microbes at two sites on the local level from extensively to intensively managed sites, which indicates that the response pattern of ammoniaoxidizing microbes in grassland soils is likely triggered to a large extent by LUI. However at a third site, where two different soil types were investigated, no correlation between LUI and potential nitrification rates was observed, and only a site-specific effect was apparent. At this site, on the one hand the specific soil type (Histosol) and the related continuous nutrient mobilization from the former peat matrix, as well as the high groundwater level, which could induce a high abundance of methane-oxidizing microbes in the top soil, may be of greater importance as a driver for potential nitrification rates and abundance of ammonia-oxidizing microbes than LUI. On the other hand, the mineral soils of this site were characterized by extreme water shortage, which may also explain the lack of potential nitrification and the abundance of ammonia-oxidizing bacteria and archaea. Thus any extrapolation of local data to regional predictions must be made with care, as factors other than LUI may be of importance if the nitrification potential of a soil is to be described.

Science of The Total Environment, 2000

In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the oc... more In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the occlusal area of the fillings were determined. Before and at select times after removal of all amalgams, concentrations of total mercury were measured by cold-vapor atomic absorption in plasma and erythrocytes as well as in urine together with the excretion rate. Absorbed daily doses were estimated from intraoral Hg emission by two separate methods. The transfer of Hg from the fillings via the oral cavity and blood to urinary excretion was evaluated according to the most representative combination of parameters. This consisted of occlusal area (1), absorbed dose (2), Hg concentration in plasma (3) and urinary excretion (4). Pairwise correlation coefficients were 0.49 for parameters 1 vs. 2, and 0.75 each for parameters 2 vs. 3 and 3 vs. 4. Within 9 days after removal of the fillings, a transient increase in Hg levels was observed in plasma only; in the group without a rubber dam, concentrations increased significantly above pre-removal values at days 1 and 3, whereas they decreased significantly below pre-removal values at day 30 in the rubber-dam group and at day 100 in both groups. Excretion rates decreased significantly at day 100 in the protected group. Peak plasma-Hg was 0.6 ng/ml on average at day 1 and decreased with halftimes of 3 and 43 days in subjects protected by a rubber dam. The results indicated that concentrations of total mercury in plasma responded rapidly to changes in the amalgam status and reflected the actual absorption most reliably. Notably, plasma-Hg levels were sensitive enough to detect a transient attenuation of the additional exposure after using a rubber dam during the removal of only a few fillings. However, being small in magnitude and lasting 100 days at best, the rubber-dam effect had minor toxicological relevance.

Zeitschrift fur Naturforschung C

Analyses of different plant stressors are often based on gene expression studies. Quantitative re... more Analyses of different plant stressors are often based on gene expression studies. Quantitative real-time RT-PCR (qRT-PCR) is the most sensitive method for the detection of low abundance transcripts. However, a critical point to note is the selection of housekeeping genes as an internal control. Many so-called 'housekeeping genes' are often affected by different stress factors and may not be suitable for use as an internal reference. We tested six housekeeping genes of European beech by qRT-PCR using the Sybr Green PCR kit. Specific primers were designed for 18S rRNA, actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH1, GAPDH2), α-tubulin, and ubiquitin-like protein. Beech saplings were treated with increased concentrations of either ozone or CO 2 . In parallel, the expression of these genes was analyzed upon pathogen infection with Phytophthora citricola. To test the applicability of these genes as internal controls under realistic outdoor conditions, sun and shade leaves of 60-year-old trees were used for comparison. The regulation of all genes was tested using a linear mixed-effect model of the R-system. Results from independent experiments showed that the only gene not affected by any treatment was actin. The expression of the other housekeeping genes varied more or less with the degree of stress applied. These results highlight the importance of undergoing an individual selection of internal control genes for different experimental conditions.

Umweltwissenschaften und Schadstoff-Forschung

Herbicides are structurally diverse chemicals that inhibit plant-specific targets, however their ... more Herbicides are structurally diverse chemicals that inhibit plant-specific targets, however their off-target and potentially differentiating side-effects are less well defined. In this study, genome-wide expression profiling based on Affymetrix AtH1 arrays was used to identify discriminating responses of Arabidopsis thaliana to five related chemicals that target two different branches of amino acid biosynthesis. The compounds included glyphosate that targets 5-enolpyruvylshikimate-3-phosphate synthase and four diverse acetolactate synthase (ALS) inhibiting compounds. The ALS inhibitors comprised three different chemical classes as well as two compounds based on the same, sulfonylurea backbone. In contrast to glyphosate, which affected only a few transcripts, ALS inhibitors led to numerous transcriptional changes which indicated off-target effects related to C-metabolism, secondary metabolism, cell wall modification and growth. The expression pattern of a set of 101 genes provided a s...

Applied Soil Ecology, 2015

ABSTRACT Application of manure for soil fertilization is a common practice in arable and pasture ... more ABSTRACT Application of manure for soil fertilization is a common practice in arable and pasture soils. As antibiotics are regularly used in animal husbandry, these compounds often enter the soil via manure application. The effects of antibiotics on microbial communities, however, might depend on soil moisture, as water availability may influence both the fate of the compound and the activity of the microbes. To test this hypothesis, we investigated the effects of the application of manure containing the antibiotic sulfadiazine (SDZ) on the abundance and activity of nitrifies and denitrifies in soil, based on the copy number of marker genes and their related potential activities, as affected by different moisture regimes. We observed significant effects of SDZ on potential denitrification activity, but those were not influenced by the soil moisture regime. Nevertheless, neither SDZ nor changes on moisture significantly affected the abundance of denitrifies. In contrast, both potential nitrification activity and abundance of ammonia oxidizing bacteria were significantly affected by the application of manure containing SDZ and moisture regime. Interestingly, no effects were observed for ammonia oxidizing archaea. Overall, our data show that soil moisture modulates the effects of antibiotics in soil microbial communities, and we recommend to include this parameter in the risk assessment of new chemicals.

Our data demonstrated: (i) a clear transcriptional ozone response of juvenile beech. (ii) Althoug... more Our data demonstrated: (i) a clear transcriptional ozone response of juvenile beech. (ii) Although the expression profile was not identical in both years, a common tendency of gene expression was obvious. The more pronounced changes in 2006 may be explained by a higher stomatal conductance in 2006 compared to 2005. (iii) (iv) First proteome analyses also indicated an ozone response of beech leaves.

Umweltwissenschaften und Schadstoff-Forschung, 2002

... Multikriterielle Bewertungs-und Entscheidungshilfe-Instrumente Stefan Pudenz 1, Rainer Briigg... more ... Multikriterielle Bewertungs-und Entscheidungshilfe-Instrumente Stefan Pudenz 1, Rainer Briiggemann 2, Kristina Voigt 3 und Gerhard Welzl 3 ... Match 42, 7-21 [16] Randic M, Vracko M, Novic M, Basak SC (2000): On ordering of folded structures. ...

Umweltwissenschaften und Schadstoff-Forschung, 2002

Zusammenfassung Ziel und Hintergrund Umweltmonitoring-Informationen über einige Luftschadstoffe ... more Zusammenfassung Ziel und Hintergrund Umweltmonitoring-Informationen über einige Luftschadstoffe wie Ozon (O3), Stickstoffdioxid (NO2), Stickstoffmonoxid (NO), Kohlendioxid (CO2) und Kohlenmonoxid (CO), zuweilen auch Schwebstaub, Benzol und andere Umweltchemikalien stehen der Öffentlichkeit im Internet zur freien Verfügung. Da fast alle Bundesländer bzw. Städte unterschiedliche Informationssysteme etabliert haben, ist eine Gegenüberstellung der Systeme mit deren Vor- und Nachteilen von großem Interesse. Schwerpunkte Es werden Umweltmonitoring-Informationssysteme

Zeitschrift für Naturforschung. C, Journal of biosciences

Analyses of different plant stressors are often based on gene expression studies. Quantitative re... more Analyses of different plant stressors are often based on gene expression studies. Quantitative real-time RT-PCR (qRT-PCR) is the most sensitive method for the detection of low abundance transcripts. However, a critical point to note is the selection of housekeeping genes as an internal control. Many so-called 'housekeeping genes' are often affected by different stress factors and may not be suitable for use as an internal reference. We tested six housekeeping genes of European beech by qRT-PCR using the Sybr Green PCR kit. Specific primers were designed for 18S rRNA, actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH1, GAPDH2), a-tubulin, and ubiquitin-like protein. Beech saplings were treated with increased concentrations of either ozone or CO2. In parallel, the expression of these genes was analyzed upon pathogen infection with Phytophthora citricola. To test the applicability of these genes as internal controls under realistic outdoor conditions, sun and shade leaves ...

Soil Biology and Biochemistry, 2011

Effects of decomposers on plant growth are generally ascribed to nutrient mobilization. However, ... more Effects of decomposers on plant growth are generally ascribed to nutrient mobilization. However, Collembola, which are ubiquitous and abundant decomposers in soil, are known to alter root morphology with, in some cases, the nutrient content of plants remaining unaffected. We studied the interaction of Collembola (Protaphorura fimata) with the model plant Arabidopsis thaliana in order to link phenotypic responses of A. thaliana to decomposers using changes in gene expression. Collembola reduced the growth of A. thaliana during early growth stages, but this decrease was compensated later. Expression analyses revealed striking differences in the response of plant roots and shoots three and six days after exposure of Arabidopsis to Collembola. Among the specifically affected transcripts in roots, the induction of auxin-responsive genes was significantly increased after six days, suggesting that P. fimata provoked auxin-related signalling in roots. In shoots, transcriptional changes were more diverse and functional categories involved in defence and metabolic re-arrangements were significantly affected. These responses might have been related to the transitory reduction in growth which presumably was caused by Collembola feeding on and/or damaging roots. The results suggest that Collembola may improve plant resistance against the attack by herbivores by stimulating the production of secondary compounds while concomitantly compensating the costs of producing them by fostering root growth and nutrient exploitation.

The Science of the total environment, Jan 15, 2010

A soil-borne microbial community isolated from a contaminated site was previously shown to minera... more A soil-borne microbial community isolated from a contaminated site was previously shown to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB) under aerobic conditions. The key degrader in this community was identified as Bordetella sp. F2. The objective of the study was to test the capacity of the microbial community to degrade a complex mixture of 27 organochlorine compounds and pesticides (OCPs) commonly detected in the environment. The hypothesis was that the microbes would utilize the OCPs as carbon sources at the low concentrations of these compounds, found in natural waters and soil solution. The study was carried out in liquid culture and the changes in concentration of the OCPs were monitored using GC-MS. Data analysis was done using a multivariate analysis method similar to Principal Response Curve (PRC) analysis. Contrary to expectations, the data analysis showed a general trend where higher concentrations were observed in the microbially treated samples relative to the control...

Acta hydrochimica et hydrobiologica, 2005

ABSTRACT

Plant secondary metabolism significantly contributes to defensive measures against adverse abioti... more Plant secondary metabolism significantly contributes to defensive measures against adverse abiotic and biotic cues. To investigate stress-induced, transcriptional alterations of underlying effector gene families, which encode enzymes acting consecutively in secondary metabolism and defense reactions, a DNA array (MetArray) harboring gene-specific probes was established. It comprised complete sets of genes encoding 109 secondary product glycosyltransferases and 63 glutathione-utilizing enzymes along

Trees, 2009

The shikimate pathway plays a central role in the formation of aromatic intermediates in the prod... more The shikimate pathway plays a central role in the formation of aromatic intermediates in the production of stilbenes, flavonoids and lignins. Ozone effects on the levels of transcripts in this pathway were studied in saplings of European beech. Complementary DNA (cDNA) clones of all genes of this pathway were isolated, and quantitative real-time RT-PCR (qRT-PCR) using RNA isolated from leaves of ozone-treated saplings showed a strong induction of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase 1 (DAHPS1), DAHPS3, 3-dehydroquinate dehydratase/ shikimate dehydrogenase (DHQD/SD), 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), and chorismate mutase (CM) transcripts. In contrast, DAHPS2, 3-dehydroquinate synthase (DHQS), shikimate kinase (SK), and chorismate synthase (CS) transcripts were only weakly induced. Earliest induction could be observed after 2 days of ozone treatment for DAHPS1, SK, EPSPS and CM. The coordinated regulation was evident for 3-5 weeks after the onset of ozone fumigation, and increased transcript levels were still detectable after another 7 weeks. Western blot analyses of DAHPS3 and DHQD/SD showed an increased protein level in agreement with the increased transcription levels. Ozone-dependent leaf lesions appeared 7 weeks after onset of ozone exposure. Strongly elevated were levels of conjugates of salicylic (SA) and gentisic acids (GA), either derived directly from chorismate, the key product of the shikimate pathway, or via phenylalanine, cinnamic, and benzoic acids. Concentrations of cell wall-bound phenolic compounds increased in both control and ozone-treated saplings with the latter showing slightly higher levels. Interestingly, however, this increase of cell wall-bound phenolics was accompanied by a decrease of soluble phenolics, which may indicate their deposition into the cell wall.

Toxicology Mechanisms and Methods, 2004

Alongside food, emissions from amalgam fillings are an essential contribution to man&... more Alongside food, emissions from amalgam fillings are an essential contribution to man's mercury burden. Previous methods for the determination of intraoral mercury vapor (Hg degrees ) release used principally some form of preconcentration of Hg on gold (film or wool), allowing relatively few measurements with unknown precision and sensitivity at selected times. Recently available computer-controlled Hg detectors operating on Zeeman atomic absorption spectroscopy (ZAAS) facilitate the direct real-time measurement of Hg degrees concentrations. It was the aim to adapt this method for a comparative investigation of emission processes from fillings in situ and from amalgam specimens in vitro. In addition to the ZAAS instrument, the apparatus consisted of a pump, magnetic valves, an electronic flow controller and a handle with a disposable mouth piece for aspiration of oral air. A programmable timer integrated the computer-controlled instrument operation and the data collection into a standard sampling protocol. A fast exponential decay of the emission was found after stimulation of amalgam specimens and of fillings in situ (halftimes 8.6 and 10.7 min). Precision was evaluated by a series of measurements on a single patient which indicated a consistently low coefficient of variation between 18% and 25%. After insertion of a few new fillings, sensitivity was high enough to detect a significant increase in emission against the background emission from the majority of old fillings. Zeeman-AAS in connection with a semi-automated sampling protocol and data storage provides precise in-situ measurements of Hg degrees emission from dental amalgam with real-time resolution. This facilitates the detailed exploration of the Hg degrees release kinetics and the applicability to large-scale studies.

The ISME Journal, 2012

Alkanes are major constituents of plant-derived waxy materials. In this study, we investigated th... more Alkanes are major constituents of plant-derived waxy materials. In this study, we investigated the abundance, community structure and activity of bacteria harbouring the alkane monooxygenase gene alkB, which catalyses a major step in the pathway of aerobic alkane degradation in the litter layer, the litter-soil interface and in bulk soil at three time points during the degradation of maize and pea plant litter (2, 8 and 30 weeks) to improve our understanding about drivers for microbial performance in different soil compartments. Soil cores of different soil textures (sandy and silty) were taken from an agricultural field and incubated at constant laboratory conditions. The abundance of alkB genes and transcripts (by qPCR) as well as the community structure (by terminal restriction fragment polymorphism fingerprinting) were measured in combination with the concentrations and composition of alkanes. The results obtained indicate a clear response pattern of all investigated biotic and abiotic parameters depending on the applied litter material, the type of soil used, the time point of sampling and the soil compartment studied. As expected the distribution of alkanes of different chain length formed a steep gradient from the litter layer to the bulk soil. Mainly in the two upper soil compartments community structure and abundance patterns of alkB were driven by the applied litter type and its degradation. Surprisingly, the differences between the compartments in one soil were more pronounced than the differences between similar compartments in the two soils studied. This indicates the necessity for analysing processes in different soil compartments to improve our mechanistic understanding of the dynamics of distinct functional groups of microbes.

Soil Biology and Biochemistry, 2014

ABSTRACT Spatial and temporal dynamics of microbial community structure and function in subsoils ... more ABSTRACT Spatial and temporal dynamics of microbial community structure and function in subsoils have been rarely studied in the past. In this paper we present data on how bacterial communities as well as selected functional groups of microbes change in the rhizosphere, the drilosphere, and in bulk soil over time in topsoil as well as in subsoil. We show that the overall richness of bacteria and abundance of nitrifiers and denitrifiers decreases in bulk soil with soil depth. However, these effects were not or to a much lower degree observed in the rhizosphere and the drilosphere. Temporal fluctuations contributed by far less than spatial factors to the dynamics of bacterial communities and abundance of nitrifiers and denitrifiers in all compartments independent from the soil depth.

Soil Biology and Biochemistry, 2014

In this study, drivers for ammonia-oxidation and the related microbial communities (ammonia-oxidi... more In this study, drivers for ammonia-oxidation and the related microbial communities (ammonia-oxidizing bacteria and archaea) were investigated in grassland soils on the local as well as on the regional scale focusing on the role of land-use intensity (LUI). To this end, 150 sites from three distinct regions across Germany were selected, covering the whole range of LUI levels (from natural grasslands up to intensive managed meadows). Furthermore, the role of contrasting soil types was analyzed in one of the regions (high vs low organic matter content) for ammonia-oxidation. We revealed a significant increase in potential nitrification rates and abundance of ammonia-oxidizing microbes at two sites on the local level from extensively to intensively managed sites, which indicates that the response pattern of ammoniaoxidizing microbes in grassland soils is likely triggered to a large extent by LUI. However at a third site, where two different soil types were investigated, no correlation between LUI and potential nitrification rates was observed, and only a site-specific effect was apparent. At this site, on the one hand the specific soil type (Histosol) and the related continuous nutrient mobilization from the former peat matrix, as well as the high groundwater level, which could induce a high abundance of methane-oxidizing microbes in the top soil, may be of greater importance as a driver for potential nitrification rates and abundance of ammonia-oxidizing microbes than LUI. On the other hand, the mineral soils of this site were characterized by extreme water shortage, which may also explain the lack of potential nitrification and the abundance of ammonia-oxidizing bacteria and archaea. Thus any extrapolation of local data to regional predictions must be made with care, as factors other than LUI may be of importance if the nitrification potential of a soil is to be described.

Science of The Total Environment, 2000

In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the oc... more In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the occlusal area of the fillings were determined. Before and at select times after removal of all amalgams, concentrations of total mercury were measured by cold-vapor atomic absorption in plasma and erythrocytes as well as in urine together with the excretion rate. Absorbed daily doses were estimated from intraoral Hg emission by two separate methods. The transfer of Hg from the fillings via the oral cavity and blood to urinary excretion was evaluated according to the most representative combination of parameters. This consisted of occlusal area (1), absorbed dose (2), Hg concentration in plasma (3) and urinary excretion (4). Pairwise correlation coefficients were 0.49 for parameters 1 vs. 2, and 0.75 each for parameters 2 vs. 3 and 3 vs. 4. Within 9 days after removal of the fillings, a transient increase in Hg levels was observed in plasma only; in the group without a rubber dam, concentrations increased significantly above pre-removal values at days 1 and 3, whereas they decreased significantly below pre-removal values at day 30 in the rubber-dam group and at day 100 in both groups. Excretion rates decreased significantly at day 100 in the protected group. Peak plasma-Hg was 0.6 ng/ml on average at day 1 and decreased with halftimes of 3 and 43 days in subjects protected by a rubber dam. The results indicated that concentrations of total mercury in plasma responded rapidly to changes in the amalgam status and reflected the actual absorption most reliably. Notably, plasma-Hg levels were sensitive enough to detect a transient attenuation of the additional exposure after using a rubber dam during the removal of only a few fillings. However, being small in magnitude and lasting 100 days at best, the rubber-dam effect had minor toxicological relevance.