Comparative metagenomics of biogas-producing microbial communities from production-scale biogas plants operating under wet or dry fermentation conditions

Stolze Y, Zakrzewski M, Maus I, et al. Comparative metagenomics of biogas-producing microbial communities from production-scale biogas plants operating under wet or dry fermentation conditions. Biotechnology for Biofuels. 2015;8(1): 14.Background Decomposition of biomass for biogas production can be practiced under wet and dry fermentation conditions. In contrast to the dry fermentation technology, wet fermentation is characterized by a high liquid content and a relatively low total solid content. In this study, the composition and functional potential of a biogas-producing microbial community in an agricultural biogas reactor operating under wet fermentation conditions was analyzed by a metagenomic approach applying 454-pyrosequencing. The obtained metagenomic dataset and corresponding 16S rRNA gene amplicon sequences were compared to the previously sequenced comparable metagenome from a dry fermentation process, meeting explicitly identical boundary conditions regarding sample and community DNA preparation, sequencing technology, processing of sequence reads and data analyses by bioinformatics tools. Results High-throughput metagenome sequencing of community DNA from the wet fermentation process applying the pyrosequencing approach resulted in 1,532,780 reads, with an average read length of 397 bp, accounting for approximately 594 million bases of sequence information in total. Taxonomic comparison of the communities from wet and dry fermentation revealed similar microbial profiles with Bacteria being the predominant superkingdom, while the superkingdom Archaea was less abundant. In both biogas plants, the bacterial phyla Firmicutes, Bacteroidetes, Spirochaetes and Proteobacteria were identified with descending frequencies. Within the archaeal superkingdom, the phylum Euryarchaeota was most abundant with the dominant class Methanomicrobia. Functional profiles of the communities revealed that environmental gene tags representing methanogenesis enzymes were present in both biogas plants in comparable frequencies. 16S rRNA gene amplicon high-throughput sequencing disclosed differences in the sub-communities comprising methanogenic Archaea between both processes. Fragment recruitments of metagenomic reads to the reference genome of the archaeon Methanoculleus bourgensis MS2T revealed that dominant methanogens within the dry fermentation process were highly related to the reference. Conclusions Although process parameters, substrates and technology differ between the wet and dry biogas fermentations analyzed in this study, community profiles are very similar at least at higher taxonomic ranks, illustrating that core community taxa perform key functions in biomass decomposition and methane synthesis. Regarding methanogenesis, Archaea highly related to the type strain M. bourgensis MS2T dominate the dry fermentation process, suggesting the adaptation of members belonging to this species to specific fermentation process parameters

Water- and solute transport in Eutric Vertisols of Lower Saxony by example of a red claystone (Upper Bunter, so)

Unklarheiten bei der Modellierung und bei den Bilanzgrößen des Wasser- und Nährstoffhaushaltes in vorangegangenen Arbeiten führen zur Frage, ob die bisher gebräuchlichen Modellvorstellungen zum Wasser- und Nährstofftransport, die auf Böden mit hohem Schluff- oder Sandanteil erfolgreich angewendet werden, auch auf Böden mit hohem Tongehalt (Pelosolen) und damit hoher Strukturbildung, anwendbar sind. Tone bilden geohydrologische Barrieren. Die zentrale Fragestellung ist die nach dem Verbleib des über die Verdunstung hinaus fallende Niederschlagswassers. Angewendet werden verschiedene Lysimetermethoden, Tracermethoden, bodenphysikalische und feldbodenkundliche Methoden. Die wichtigsten Ergebnisse zum Wassertransport und -haushalt sind: Pelosole sind im gequollenen Zustand durchlässig. Wassertransport erfolgt in wenigen bevorzugten lateralen und vertikalen Bahnen mit hohen Porenwassergeschwindigkeiten, welches die Anwendung von einfachen mathematischen Modellen verbietet. Die lateralen Flüsse orientieren sich nicht an der Geländemorphologie, sondern an eiszeitlich überprägten Strukturen. Die gemessene gesättigte Wasserleitfähigkeit an großen Bodenmonolithen ist um zwei Zehnerpotenzen größer an Stechzylindern. Der Stofftransport erfolgt präferenziell mit geringer Diffusion aus den bevorzugten Bahnen in Bodenaggregate hinein. Wassergebundener Partikeltransport aus dem Oberboden wird beobachtet, die Auswaschung von bodengebundenen Phosphat ist also möglich. Eine Minderung dieser Austräge ist durch geeignete Bewirtschaftungsmaßnahmen ist. Weiterhin wird gezeigt, dass die unterschiedlich intensive eiszeitliche Verwitterung von Pelitgesteinen die bodenphysikalischen Eigenschaften maßgeblich beeinflusst. Die Anwendung der Reichsbodenschätzung auf zwei Leitprofile ergibt fälschlicherweise, dass dem Profil mit der geringeren nutzbaren Feldkapazität eine höhere Bodenzahl zugeordnet wird. Als Grund für die Unterschiede in der nutzbaren Feldkapazität wird das Mikrogefüge angesehen, welches im Gelände bei der Schätzung nicht beachtet wird, in Zukunft jedoch berücksichtigt werden muss

How can soil monitoring networks be used to improve predictions of organic carbon pool dynamics and CO2 fluxes in agricultural soils?

Abstract As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5–10 years interval) are used with densities of one site per 10–1,040 km². For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6–6.5 Mg C ha−1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha−1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i.e. a spatially implicit upscaling approach). Keywords Soil monitoring networks - Soil organic carbon - Modeling - Sampling desig