RESUMEN

DDT transformation to DDD in soil is the most commonly reported pathway under anaerobic conditions. A few instances of DDT conversion to products other than DDD/DDE have been reported under aerobic conditions and hardly any under anaerobic conditions. In particular, few reports exist on the anaerobic degradation of DDT in African tropical soils, despite DDT contamination arising from obsolete pesticide stockpiles in the continent as well as new contamination from DDT use for mosquito and tsetse fly control. Moreover, the development of possible remediation strategies for contaminated sites demands adequate understanding of different soil processes and their effect on DDT persistence, hence necessitating the study. The aim of this work was to study the effect of simulated anaerobic conditions and slow-release carbon sources (compost) on the dissipation of DDT in two tropical clay soils (paddy soil and field soil) amenable to periodic flooding. The results showed faster DDT dissipation in the field soil but higher metabolite formation in the paddy soil. To explain this paradox, the levels of dissolved organic carbon and carbon mineralization (CH4 and CO2) were correlated with p,p-DDT and p,p-DDD concentrations. It was concluded that DDT underwent reductive degradation (DDD pathway) in the paddy soil and both reductive (DDD pathway) and oxidative degradation (non-DDD pathway) in the field soil.

Asunto(s)

DDT/química , Diclorodifenildicloroetano/química , Plaguicidas/química , Contaminantes del Suelo/química , Suelo/química , Carbono , Arcilla , Compostaje , DDT/análisis , Restauración y Remediación Ambiental , Clima Tropical

RESUMEN

The frequency of extreme drought and heavy rain events during the vegetation period will increase in Central Europe according to future climate change scenarios, which will affect the functioning of terrestrial ecosystems in multiple ways. In this study, we simulated an extreme drought event (40 days) at two different vegetation periods (spring and summer) to investigate season-related effects of drought and subsequent rewetting on nitrifiers and denitrifiers in a grassland soil. Abundance of the microbial groups of interest was assessed by quantification of functional genes (amoA, nirS/nirK and nosZ) via quantitative real-time PCR. Additionally, the diversity of ammonia-oxidizing archaea was determined based on fingerprinting of the archaeal amoA gene. Overall, the different time points of simulated drought and rewetting strongly influenced the obtained response pattern of microbial communities involved in N turnover as well as soil ammonium and nitrate dynamics. In spring, gene abundance of nirS was irreversible reduced after drought whereas nirK and nosZ remained unaffected. Furthermore, community composition of ammonia-oxidizing archaea was altered by subsequent rewetting although amoA gene abundance remained constant. In contrast, no drought/rewetting effects on functional gene abundance or diversity pattern of nitrifying archaea were observed in summer. Our results showed (I) high seasonal dependency of microbial community responses to extreme events, indicating a strong influence of plant-derived factors like vegetation stage and plant community composition and consequently close plant-microbe interactions and (II) remarkable resistance and/or resilience of functional microbial groups involved in nitrogen cycling to extreme weather events what might indicate that microbes in a silty soil are better adapted to stress situations as expected.

Asunto(s)

Archaea/crecimiento & desarrollo , Desnitrificación/fisiología , Pradera , Microbiota/fisiología , Nitrificación/fisiología , Microbiología del Suelo , Suelo , Archaea/genética , Genes Arqueales

RESUMEN

Glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) have frequently been detected in surface water and groundwaters. Since adequate glyphosate mineralization in soil may reduce its losses to environment, improved understanding of site specific factors underlying pesticide mineralization in soils is needed. The aim of this study was to investigate the relationship between soil properties and glyphosate mineralization. To establish a sound basis for resilient correlations, the study was conducted with a large number of 21 agricultural soils, differing in a variety of soil parameters, such as soil texture, soil organic matter content, pH, exchangeable ions etc. The mineralization experiments were carried out with 14C labelled glyphosate at a soil water tension of -15 kPa and at a soil density of 1.3 g cm-3 at 20 ±â€¯1 °C for an incubation period of 32 days. The results showed that the mineralization of glyphosate in different agricultural soils varied to a great extent, from 7 to 70% of the amount initially applied. Glyphosate mineralization started immediately after application, the highest mineralization rates were observed within the first 4 days in most of the 21 soils. Multiple regression analysis revealed exchangeable acidity (H+ and Al3+), exchangeable Ca2+ ions and ammonium lactate extractable K to be the key soil parameters governing glyphosate mineralization in the examined soils. A highly significant negative correlation between mineralized glyphosate and NaOH-extractable residues (NaOH-ER) in soils strongly suggests that NaOH-ER could be used as a simple and reliable parameter for evaluating the glyphosate mineralization capacity. The NaOH-ER were composed of glyphosate, unknown 14C-residues, and AMPA (12%-65%, 3%-34%, 0%-11% of applied 14C, respectively). Our results highlighted the influential role of soil exchangeable acidity, which should therefore be considered in pesticide risk assessments and management to limit efficiently the environmental transfers of glyphosate.

RESUMEN

In our mouse model, gastric acid-suppression is associated with antigen-specific IgE and anaphylaxis development. We repeatedly observed non-responder animals protected from food allergy. Here, we aimed to analyse reasons for this protection. Ten out of 64 mice, subjected to oral ovalbumin (OVA) immunizations under gastric acid-suppression, were non-responders without OVA-specific IgE or IgG1 elevation, indicating protection from allergy. In these non-responders, allergen challenges confirmed reduced antigen uptake and lack of anaphylactic symptoms, while in allergic mice high levels of mouse mast-cell protease-1 and a body temperature reduction, indicative for anaphylaxis, were determined. Upon OVA stimulation, significantly lower IL-4, IL-5, IL-10 and IL-13 levels were detected in non-responders, while IL-22 was significantly higher. Comparison of fecal microbiota revealed differences of bacterial communities on single bacterial Operational-Taxonomic-Unit level between the groups, indicating protection from food allergy being associated with a distinct microbiota composition in a non-responding phenotype in this mouse model.

Asunto(s)

Anafilaxia/microbiología , Hipersensibilidad a los Alimentos/microbiología , Microbiota , Administración Oral , Alérgenos/administración & dosificación , Anafilaxia/inmunología , Animales , Antiulcerosos/farmacología , Bacterias/aislamiento & purificación , Citocinas/inmunología , Modelos Animales de Enfermedad , Heces/microbiología , Femenino , Hipersensibilidad a los Alimentos/inmunología , Ácido Gástrico , Inmunización , Inmunoglobulina A/inmunología , Inmunoglobulina E/inmunología , Inmunoglobulina G/inmunología , Intestinos/anatomía & histología , Intestinos/inmunología , Ratones Endogámicos BALB C , Ovalbúmina/administración & dosificación , Ovalbúmina/sangre , Bazo/citología , Bazo/inmunología , Estómago/anatomía & histología , Estómago/inmunología , Sucralfato/farmacología

RESUMEN

In the first tier risk assessment (RA) of pesticides, risk for aquatic communities is estimated by using results from standard laboratory tests with algae, daphnids and fish for single pesticides such as herbicides, fungicides, and insecticides. However, fungi as key organisms for nutrient cycling in ecosystems as well as multiple pesticide applications are not considered in the RA. In this study, the effects of multiple low pesticide pulses using regulatory acceptable concentrations (RACs) on the dynamics of non-target aquatic fungi were investigated in a study using pond mesocosm. For that, fungi colonizing black alder (Alnus glutinosa) leaves were exposed to multiple, low pulses of 11 different pesticides over a period of 60days using a real farmer's pesticide application protocol for apple cropping. Four pond mesocosms served as treatments and 4 as controls. The composition of fungal communities colonizing the litter material was analyzed using a molecular fingerprinting approach based on the terminal Restriction Fragment Length Polymorphism (t-RFLP) of the fungal Internal Transcribed Spacer (ITS) region of the ribonucleic acid (RNA) gene(s). Our data indicated a clear fluctuation of fungal communities based on the degree of leaf litter degradation. However significant effects of the applied spraying sequence were not observed. Consequently also degradation rates of the litter material were not affected by the treatments. Our results indicate that the nutrient rich environment of the leaf litter material gave fungal communities the possibility to express genes that induce tolerance against the applied pesticides. Thus our data may not be transferred to other fresh water habitats with lower nutrient availability.

Asunto(s)

Fenómenos Ecológicos y Ambientales , Monitoreo del Ambiente , Hongos/efectos de los fármacos , Plaguicidas/toxicidad , Microbiología del Agua , Contaminantes Químicos del Agua/toxicidad , Hongos/fisiología , Fungicidas Industriales/análisis , Fungicidas Industriales/toxicidad , Herbicidas/análisis , Herbicidas/toxicidad , Insecticidas/análisis , Insecticidas/toxicidad , Plaguicidas/análisis , Hojas de la Planta , Contaminantes Químicos del Agua/análisis

RESUMEN

In this study, we investigated the impact of soil pH on the diversity and abundance of archaeal ammonia oxidizers in 27 different forest soils across Germany. DNA was extracted from topsoil samples, the amoA gene, encoding ammonia monooxygenase, was amplified; and the amplicons were sequenced using a 454-based pyrosequencing approach. As expected, the ratio of archaeal (AOA) to bacterial (AOB) ammonia oxidizers' amoA genes increased sharply with decreasing soil pH. The diversity of AOA differed significantly between sites with ultra-acidic soil pH (<3.5) and sites with higher pH values. The major OTUs from soil samples with low pH could be detected at each site with a soil pH <3.5 but not at sites with pH >4.5, regardless of geographic position and vegetation. These OTUs could be related to the Nitrosotalea group 1.1 and the Nitrososphaera subcluster 7.2, respectively, and showed significant similarities to OTUs described from other acidic environments. Conversely, none of the major OTUs typical of sites with a soil pH >4.6 could be found in the ultra- and extreme acidic soils. Based on a comparison with the amoA gene sequence data from a previous study performed on agricultural soils, we could clearly show that the development of AOA communities in soils with ultra-acidic pH (<3.5) is mainly triggered by soil pH and is not influenced significantly by the type of land use, the soil type, or the geographic position of the site, which was observed for sites with acido-neutral soil pH.

Asunto(s)

Amoníaco/metabolismo , Archaea/fisiología , Bosques , Microbiota , Microbiología del Suelo , Alemania , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Suelo/química

RESUMEN

In the present study, the influence of the land use intensity on the diversity of ammonia oxidizing bacteria (AOB) and archaea (AOA) in soils from different grassland ecosystems has been investigated in spring and summer of the season (April and July). Diversity of AOA and AOB was studied by TRFLP fingerprinting of amoA amplicons. The diversity from AOB was low and dominated by a peak that could be assigned to Nitrosospira. The obtained profiles for AOB were very stable and neither influenced by the land use intensity nor by the time point of sampling. In contrast, the obtained patterns for AOA were more complex although one peak that could be assigned to Nitrosopumilus was dominating all profiles independent from the land use intensity and the sampling time point. Overall, the AOA profiles were much more dynamic than those of AOB and responded clearly to the land use intensity. An influence of the sampling time point was again not visible. Whereas AOB profiles were clearly linked to potential nitrification rates in soil, major TRFs from AOA were negatively correlated to DOC and ammonium availability and not related to potential nitrification rates.

Asunto(s)

Amoníaco/metabolismo , Archaea/clasificación , Bacterias/clasificación , Filogenia , Microbiología del Suelo , Agricultura/métodos , Archaea/metabolismo , Bacterias/metabolismo , Ecosistema , Fertilizantes , Alemania , Nitrificación , Oxidorreductasas/genética , Poaceae , Polimorfismo de Longitud del Fragmento de Restricción , Estaciones del Año

RESUMEN

Microbial communities play an important role in cheese ripening and determine the flavor and taste of different cheese types to a large extent. However, under adverse conditions human pathogens may colonize cheese samples during ripening and may thus cause severe outbreaks of diarrhoea and other diseases. Therefore in the present study we investigated the bacterial community structure of three raw ewe's milk cheese types, which are produced without the application of starter cultures during ripening from two production sites based on fingerprinting in combination with next generation sequencing of 16S rRNA gene amplicons. Overall a surprisingly high diversity was found in the analyzed samples and overall up to 213 OTU97 could be assigned. 20 of the major OTUs were present in all samples and include mostly lactic acid bacteria (LAB), mainly Lactococcus, and Enterococcus species. Abundance and diversity of these genera differed to a large extent between the 3 investigated cheese types and in response to the ripening process. Also a large number of non LAB genera could be identified based on phylogenetic alignments including mainly Enterobacteriaceae and Staphylococcacae. Some species belonging to these two families could be clearly assigned to species which are known as potential human pathogens like Staphylococcus saprophyticus or Salmonella spp. However, during cheese ripening their abundance was reduced. The bacterial genera, namely Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, Brevibacterium, Corynebacterium, Clostridium, Staphylococcus, Thermoanerobacterium, E. coli, Hafnia, Pseudomonas, Janthinobacterium, Petrotoga, Kosmotoga, Megasphaera, Macrococcus, Mannheimia, Aerococcus, Vagococcus, Weissella and Pediococcus were identified at a relative low level and only in selected samples. Overall the microbial composition of the used milk and the management of the production units determined the bacterial community composition for all cheese types to a large extend, also at the late time points of cheese ripening.

Asunto(s)

Bacterias/crecimiento & desarrollo , Queso/microbiología , Microbiota , Leche/microbiología , Animales , Bacterias/genética , Secuencia de Bases , Croacia , Femenino , Genes Bacterianos , Humanos , Microbiota/genética , Datos de Secuencia Molecular , Filogenia , Polimorfismo de Longitud del Fragmento de Restricción/genética , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Ovinos

RESUMEN

Understanding factors driving the ecology of N cycling microbial communities is of central importance for sustainable land use. In this study we report changes of abundance of denitrifiers, nitrifiers and nitrogen-fixing microorganisms (based on qPCR data for selected functional genes) in response to different land use intensity levels and the consequences for potential turnover rates. We investigated selected grassland sites being comparable with respect to soil type and climatic conditions, which have been continuously treated for many years as intensely used meadows (IM), intensely used mown pastures (IP) and extensively used pastures (EP), respectively. The obtained data were linked to above ground biodiversity pattern as well as water extractable fractions of nitrogen and carbon in soil. Shifts in land use intensity changed plant community composition from systems dominated by s-strategists in extensive managed grasslands to c-strategist dominated communities in intensive managed grasslands. Along the different types of land use intensity, the availability of inorganic nitrogen regulated the abundance of bacterial and archaeal ammonia oxidizers. In contrast, the amount of dissolved organic nitrogen determined the abundance of denitrifiers (nirS and nirK). The high abundance of nifH carrying bacteria at intensive managed sites gave evidence that the amounts of substrates as energy source outcompete the high availability of inorganic nitrogen in these sites. Overall, we revealed that abundance and function of microorganisms involved in key processes of inorganic N cycling (nitrification, denitrification and N fixation) might be independently regulated by different abiotic and biotic factors in response to land use intensity.

Asunto(s)

Bacterias/genética , Ecosistema , Ciclo del Nitrógeno , Nitrógeno/análisis , Poaceae/fisiología , Microbiología del Suelo , Agricultura , Bacterias/metabolismo , Biodiversidad , Desnitrificación , Genes Bacterianos , Nitrificación , Nitrógeno/metabolismo , Suelo

RESUMEN

The plant root interface is a hot spot for microbial activities. Root exudates are the key compounds that drive microbial performance. However quality and amount of root exudates are highly dynamic in time and space, thus a direct influence of a single compound on a microbial community composition is fairly impossible to study in nature. Therefore it was the aim of this project to develop an artificial root model (ARM), and investigate the influence of three compounds which have often been described as root exudates acting as model compounds for carbohydrates, organic acids and amino acids (glucose, malic acid and serine) on the development of bacterial communities and time on the ARM based on 16S rRNA derived TRFLP pattern. The ARM consisted of a slide covered with low melting agarose, where 8 different compounds which have been described as typical root exudates were embedded. The ARMs were incubated in soil for 2, 5, 9 and 20 days, before the analysis of the developed bacterial community structure was done. The bacterial community composition was in good agreement after 9 days of incubation of the ARM in soil with the root associated microflora of Arabidopsis thaliana shortly before flowering. The single compounds of the exudates mix had different effects on the development of ARM derived bacterial communities. Whereas the experiments where glucose was omitted gave no significant differences in the development of bacterial communities over time compared to the ARM where the standard mixture of exudates had been applied, there was a pronounced effect visible mainly after two days of incubation of the ARM in the experiments where no malic acid was added to the exudate mixture. At later time points ARMs with standard exudates' mixture and those where malic acid had been omitted, the bacterial community composition did not differ. The experiments where serine was omitted mainly induced shifts in the bacterial community composition compared to the ARM with standard exudates' mixture at the latest sampling time point (20 days of incubation).

Asunto(s)

Bacterias/efectos de los fármacos , Bacterias/crecimiento & desarrollo , Biota , Modelos Teóricos , Exudados de Plantas/metabolismo , Raíces de Plantas/microbiología , Arabidopsis/microbiología , Bacterias/clasificación , Bacterias/genética , Dermatoglifia del ADN , Glucosa/metabolismo , Malatos/metabolismo , Polimorfismo de Longitud del Fragmento de Restricción , Serina/metabolismo

RESUMEN

The aim of the study was to induce and enhance the degradation of hexachlorobenzene (HCB), a highly-chlorinated persistent organic pollutant, in two ecologically different tropical soils: a paddy soil (PS) and a non-paddy soil (FS). The degradation of HCB was enhanced using two anaerobic-aerobic cycles in model laboratory experiments. There was greater degradation of HCB in the PS (half-life of 224 days) relative to the FS (half-life of 286 days). It was further shown that soils amended with compost had higher metabolite concentrations relative to the non-amended soils. In the first cycle, there was little degradation of HCB in both soils. However, in the second cycle, there was enhanced mineralization in the PS under aerobic conditions, with the compost-treated samples showing higher mineralization. There was also extensive volatilization in both soils. The metabolite pattern revealed that the increased mineralization and volatilization was due to the formation of lower chlorinated benzenes.

Asunto(s)

Silicatos de Aluminio/química , Restauración y Remediación Ambiental/métodos , Hexaclorobenceno/metabolismo , Microbiología del Suelo , Contaminantes del Suelo/metabolismo , Suelo/química , Aerobiosis , Anaerobiosis , Biodegradación Ambiental , Radioisótopos de Carbono , Arcilla , Semivida , Hexaclorobenceno/análisis , Contaminantes del Suelo/análisis , Clima Tropical

RESUMEN

Mine wastes have been considered as a source of heavy metal (HM) contamination in the environment and negatively impact many important ecosystem services provided by soils. Plants like Miscanthus, which tolerate high HM concentrations in soil, are often used for phytoremediation and provide the possibility to use these soils at least for the production of energy crops. However, it is not clear if plant growth at these sites is limited by the availability of nutrients, mainly nitrogen, as microbes in soil might be affected by the contaminant. Therefore, in this study, we investigated in a greenhouse experiment the response of ammonia-oxidizing microbes in the root-rhizosphere complex of Miscanthus × giganteus grown in soils with different levels of long-term arsenic (As) and lead (Pb) contamination. Quantitative PCR of the ammonia monooxigenease gene (amoA) was performed to assess the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) at two different points of plant growth. Furthermore, bulk soil samples before planting were analyzed. In addition, terminal restriction fragment length polymorphism (T-RFLP) analysis was used to investigate the diversity of archaeal amoA amplicons. Whereas high concentrations of As and Pb in soil (83 and 15 g/kg, respectively) resulted independent from plant growth in a clear reduction of AOA and AOB compared to the control soils with lower HM contents, in soils with contamination levels of 10 g/kg As and 0.2 g/kg Pb, only AOB were negatively affected in bulk soil samples. Diversity analysis of archaeal amoA genes revealed clear differences in T-RFLP patterns in response to the degree of HM contamination. Therefore, our results could clearly prove the different response patterns of AOA and AOB in HM-contaminated soils and the development of archaeal amoA phylotypes which are more tolerant towards HMs in soil samples from the areas that were impacted the most by mining waste, which could contribute to functional redundancy of ammonia-oxidizing microbes in soils and stability of nitrification pattern.

Asunto(s)

Amoníaco/metabolismo , Archaea/aislamiento & purificación , Bacterias/aislamiento & purificación , Metales Pesados/metabolismo , Poaceae , Rizosfera , Contaminantes del Suelo/metabolismo , Archaea/clasificación , Archaea/enzimología , Archaea/genética , Arsénico/metabolismo , Bacterias/clasificación , Bacterias/enzimología , Bacterias/genética , Plomo/metabolismo , Oxidación-Reducción , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Filogenia , Raíces de Plantas/microbiología , Poaceae/crecimiento & desarrollo , Poaceae/microbiología , Reacción en Cadena de la Polimerasa/métodos , Polimorfismo de Longitud del Fragmento de Restricción

RESUMEN

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.

Asunto(s)

Fenómenos Fisiológicos Bacterianos , Oxigenasas de Función Mixta/genética , Microbiología del Suelo , Alcanos/análisis , Alcanos/metabolismo , Bacterias/enzimología , Bacterias/genética , Biodiversidad , Densidad de Población

RESUMEN

PURPOSE: The population-based KORA (Cooperative Health Research in the Region of Augsburg [Germany]) study was used to evaluate the prevalence of eye diseases and potential interactions with general health status, laboratory data, medication, and genetic background. METHODS: In all, 2593 probands, ranging in age from 32 to 71 years (mean: 52 years), were asked in a standardized interview for the presence of cataracts, glaucoma, and corneal or retinal disorders; positive answers were validated and specified by treating ophthalmologists. Additional data came from a questionnaire or from laboratory data. RESULTS: We validated 10 probands with corneal diseases (validation rate: 32%), 26 with retinal diseases (validation rate: 60%), 40 with glaucoma (validation rate: 75%), and 100 participants with cataracts (validation rate: 88%). Glaucoma was significantly associated with increasing age, diabetes and its treatment, and the use of drugs in airway diseases. Cataracts were significantly associated with increasing age, female sex, hypertension, and diabetes. In females, cataracts were particularly associated with the use of ophthalmological corticosteroids, some antihypertensives, and antidiabetics. In contrast, cataracts in males were associated only with the use of angiotensin-converting enzyme inhibitors. We also tested some polymorphic markers; two (GJA8, CRYBB3) were significantly associated with cataracts. CONCLUSIONS: Self-reported ocular diagnoses by questionnaire showed varying degrees of accuracy; this method of data collection is valid, providing confirmation is obtained from treating ophthalmologists. It revealed a similar profile of major risk factors for cataracts (age, female sex, and diabetes) in Germany like that of other international studies. The reported associations between medical treatment and genetic polymorphisms in early-onset cataract merit further functional study.

Asunto(s)

Catarata/epidemiología , Enfermedades de la Córnea/epidemiología , Glaucoma/epidemiología , Enfermedades de la Retina/epidemiología , Adulto , Anciano , Catarata/genética , Enfermedades de la Córnea/genética , Femenino , Geografía , Alemania/epidemiología , Glaucoma/genética , Estado de Salud , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Grupos de Población , Prevalencia , Enfermedades de la Retina/genética , Factores de Riesgo , Perfil de Impacto de Enfermedad , Encuestas y Cuestionarios

RESUMEN

In many areas of China, tidal wetlands have been converted into agricultural land for rice cultivation. However, the consequences of land use changes for soil microbial communities are poorly understood. Therefore, we investigated bacterial and archaeal communities involved in inorganic nitrogen turnover (nitrogen fixation, nitrification, and denitrification) based on abundances and relative species richness of the corresponding functional genes along a soil chronosequence ranging between 50 and 2,000 years of paddy soil management compared to findings for a tidal wetland. Changes in abundance and diversity of the functional groups could be observed, reflecting the different chemical and physical properties of the soils, which changed in terms of soil development. The tidal wetland was characterized by a low microbial biomass and relatively high abundances of ammonia-oxidizing microbes. Conversion of the tidal wetlands into paddy soils was followed by a significant increase in microbial biomass. Fifty years of paddy management resulted in a higher abundance of nitrogen-fixing microbes than was found in the tidal wetland, whereas dominant genes of nitrification and denitrification in the paddy soils showed no differences. With ongoing rice cultivation, copy numbers of archaeal ammonia oxidizers did not change, while that of their bacterial counterparts declined. The nirK gene, coding for nitrite reductase, increased with rice cultivation time and dominated its functionally redundant counterpart, nirS, at all sites under investigation. Relative species richness showed significant differences between all soils with the exception of the archaeal ammonia oxidizers in the paddy soils cultivated for 100 and 300 years. In general, changes in diversity patterns were more pronounced than those in functional gene abundances.

Asunto(s)

Biodiversidad , Desnitrificación , Redes y Vías Metabólicas/genética , Nitrificación , Fijación del Nitrógeno , Microbiología del Suelo , Agricultura/métodos , Archaea/genética , Proteínas Arqueales/genética , Bacterias/genética , Proteínas Bacterianas/genética , China , Metagenoma , Oryza , Polimorfismo de Longitud del Fragmento de Restricción , Reacción en Cadena en Tiempo Real de la Polimerasa

RESUMEN

Initial ecosystems are characterized by a low availability of nutrients and a low soil organic matter content. Interactions of plants and microorganisms in such environments, particularly in relation to litter decomposition, are very important for further ecosystem development. In a litter decomposition study using an initial substrate from a former mining area, we applied the litter of two contrasting pioneer plant species (legume vs. pasture plants), Lotus corniculatus and Calamagrostis epigejos, which are commonly observed in the study area. Litter decomposition was investigated and carbon (C) translocation from litter into soil microorganisms was described by following (13) C from labelled plant litter materials into the fraction of phospholipid fatty acids. Labile C compounds of both plant litter types were easily degraded during the first 4 weeks of litter decomposition. In contrast to climax ecosystems, where the importance of fungi for litter degradation has been shown in many studies, in our experiment, data clearly indicate an outcompetition of fungi by Gram-positive bacteria as soon as available nitrogen is limited in the detritusphere.

Asunto(s)

Bacterias/metabolismo , Carbono/metabolismo , Hongos/metabolismo , Lotus/metabolismo , Poaceae/metabolismo , Microbiología del Suelo , Lotus/química , Poaceae/química

RESUMEN

The balanced proliferation and cell cycle exit of neural progenitors, by generating the appropriate amount of postmitotic progeny at the correct time and in the proper location, is required for the establishment of the highly ordered structure of the adult brain. Little is known about the extrinsic signals regulating these processes, particularly in the midbrain. Fibroblast growth factor (Fgf) 15, the mouse ortholog of FGF19 and member of an atypical Fgf subfamily, is prominently expressed in the dorsolateral midbrain of the midgestational mouse embryo. In the absence of Fgf15, dorsal midbrain neural progenitors fail to exit the cell cycle and to generate the proper amount of postmitotic neurons. We show here that this is due to the altered expression of inhibitory/neurogenic and proneural/neuronal differentiation helix-loop-helix transcription factor (TF) genes. The expression of Id1, Id3, and Hes5 was strongly increased and ectopically expanded, whereas the expression of Ascl1 (Mash1), Neurog1 (Ngn1) and Neurog2 (Ngn2) was strongly decreased and transcription of Neurod1 (NeuroD) was completely abolished in the dorsolateral midbrain of Fgf15(-/-) mice. These abnormalities were not caused by the mis-expression of cell cycle regulatory proteins such as cyclin-dependent kinase inhibitors or retinoblastoma proteins. Furthermore, human FGF19 promotes cell cycle exit of murine dorsal neural progenitors in vitro. Therefore, our data suggest that Fgf15 is a crucial signaling molecule regulating the postmitotic transition of dorsal neural progenitors and thus the initiation and proper progression of dorsal midbrain neurogenesis in the mouse, by controlling the expression of neurogenic and proneural TFs.

Asunto(s)

Factores de Crecimiento de Fibroblastos/fisiología , Regulación del Desarrollo de la Expresión Génica , Mesencéfalo/embriología , Neurogénesis , Animales , Ciclo Celular , Células Cultivadas , Corteza Cerebral/citología , Antígeno Ki-67/análisis , Ratones , Ratones Endogámicos C57BL , Células-Madre Neurales/citología

RESUMEN

BACKGROUND: Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is a hallmark of complex and multifactorial psychiatric diseases such as anxiety and mood disorders. About 50-60% of patients with major depression show HPA axis dysfunction, i.e. hyperactivity and impaired negative feedback regulation. The neuropeptide corticotropin-releasing hormone (CRH) and its receptor type 1 (CRHR1) are key regulators of this neuroendocrine stress axis. Therefore, we analyzed CRH/CRHR1-dependent gene expression data obtained from the pituitary corticotrope cell line AtT-20, a well-established in vitro model for CRHR1-mediated signal transduction. To extract significantly regulated genes from a genome-wide microarray data set and to deduce underlying CRHR1-dependent signaling networks, we combined supervised and unsupervised algorithms. RESULTS: We present an efficient variable selection strategy by consecutively applying univariate as well as multivariate methods followed by graphical models. First, feature preselection was used to exclude genes not differentially regulated over time from the dataset. For multivariate variable selection a maximum likelihood (MLHD) discriminant function within GALGO, an R package based on a genetic algorithm (GA), was chosen. The topmost genes representing major nodes in the expression network were ranked to find highly separating candidate genes. By using groups of five genes (chromosome size) in the discriminant function and repeating the genetic algorithm separately four times we found eleven genes occurring at least in three of the top ranked result lists of the four repetitions. In addition, we compared the results of GA/MLHD with the alternative optimization algorithms greedy selection and simulated annealing as well as with the state-of-the-art method random forest. In every case we obtained a clear overlap of the selected genes independently confirming the results of MLHD in combination with a genetic algorithm. With two unsupervised algorithms, principal component analysis and graphical Gaussian models, putative interactions of the candidate genes were determined and reconstructed by literature mining. Differential regulation of six candidate genes was validated by qRT-PCR. CONCLUSIONS: The combination of supervised and unsupervised algorithms in this study allowed extracting a small subset of meaningful candidate genes from the genome-wide expression data set. Thereby, variable selection using different optimization algorithms based on linear classifiers as well as the nonlinear random forest method resulted in congruent candidate genes. The calculated interacting network connecting these new target genes was bioinformatically mapped to known CRHR1-dependent signaling pathways. Additionally, the differential expression of the identified target genes was confirmed experimentally.

Asunto(s)

Algoritmos , Biología Computacional/métodos , Perfilación de la Expresión Génica , Modelos Biológicos , Receptores de Hormona Liberadora de Corticotropina/metabolismo , Transducción de Señal , Análisis de Varianza , Animales , Línea Celular , Minería de Datos , Redes Reguladoras de Genes , Humanos , Funciones de Verosimilitud , Modelos Lineales , Distribución Normal , Análisis de Componente Principal , Ratas , Reproducibilidad de los Resultados

RESUMEN

The toxicologically relevant mercury species inorganic and organic Hg in blood are frequently determined by separate measurements of total Hg and of inorganic Hg, with their difference indicating organic Hg. It is shown that the different partition of inorganic and organic Hg between erythrocytes and plasma (e/p ratio) can be used to calculate the concentrations of either Hg species in either blood constituent from measurement of total Hg only. This was tested on the blood of different groups of volunteers. The calculated concentrations of inorganic and organic Hg in cells and plasma were then compared by linear regression with their previously measured counterparts. An accurate prediction has been found for individual levels of inorganic Hg in plasma and organic Hg in cells. These calculated levels were little affected by variations of the e/p ratios. The coincidence between calculated and measured levels of inorganic Hg in cells and organic Hg in plasma was more sensitive to alterations of the e/p ratios. In conclusion, the relevant concentrations of inorganic Hg in plasma and organic Hg in cells can reliably be calculated from measurements of total Hg and from assumed e/p ratios. This means a sizeable reduction of analytical work, and also provides specific information in cases of low-level co-exposure to both Hg species. Besides the possibility to introduce automated analyses of total Hg in mercury speciation in blood, the proposed calculation scheme has the potential to easily enlarge the data base in epidemiological and toxicological surveys of mercury exposure.

Asunto(s)

Mercurio/análisis , Compuestos Organomercuriales/análisis , Análisis Químico de la Sangre , Eritrocitos/metabolismo , Humanos , Modelos Lineales , Matemática , Mercurio/sangre , Mercurio/metabolismo , Compuestos Organomercuriales/sangre , Compuestos Organomercuriales/metabolismo , Valor Predictivo de las Pruebas

RESUMEN

Over the last few decades, the ability of rhizosphere bacteria to promote plant growth has been considered to be of scientific, ecological, and economic interest. The properties and mechanisms of interaction of these root-colonizing bacteria have been extensively investigated, and plant protection agents that are based on these bacterial strains have been developed for agricultural applications. In the present study, the root colonization of barley by Pseudomonas sp. DSMZ 13134, that is contained in the commercially available plant protection agent Proradix, was examined using the fluorescence in situ hybridization method with oligonucleotide probes and specific gfp-tagging of the inoculant strain in combination with confocal laser scanning microscopy. In the first phase of root colonization, the inoculant strain competed successfully with seed and soil-borne bacteria (including Pseudomonads) for the colonization of the rhizoplane. Pseudomonas sp. DSMZ 13134 could be detected in all parts of the roots, although it did not belong to the dominant members of the root-associated bacterial community. Gfp-tagged cells were localized particularly in the root hair zone, and high cell densities were apparent on the root hair surface. To investigate the impact of the application of Proradix on the structure of the dominant root-associated bacterial community of barley, T-RFLP analyses were performed. Only a transient community effect was found until 3 weeks post-application.

Asunto(s)

Hordeum/microbiología , Raíces de Plantas/microbiología , Pseudomonas/crecimiento & desarrollo , Rizosfera , Microbiología del Suelo , Antibiosis , ADN Bacteriano/genética , Hibridación Fluorescente in Situ , Microscopía Confocal , Sondas de Oligonucleótidos , Filogenia , Polimorfismo de Longitud del Fragmento de Restricción , Pseudomonas/genética , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN