Biology subjects

Richter-Heitmann, T.

Publications and source records attributed to Richter-Heitmann, T..

5 recordsLinked to original sources

bioRxiv2023

Recovering short DNA fragments from minerals and marine sediments: a comparative study evaluating lysis and isolation approaches

Marine sediments as excellent climate archives, contain among other biomolecules substantial amounts of extracellular DNA. Through mechanisms of binding to various minerals, some of the DNA stays protected from degradation and remains preserved. While this pool of DNA represents genomic ecosystem fingerprints spanning over millions of years, the capability of current DNA extraction methods in recovering mineral-bound DNA remains poorly understood. We evaluated current sedimentary DNA extraction approaches and their ability to desorb and extract short DNA fragments from pure clay and quartz minerals as well as from different types of marine sediments. We separately investigated lysis (DNA release) and isolation steps (purification of DNA) comparing five different types of lysis buffers across two commonly used DNA isolation approaches: silica magnetic beads and liquid-phase organic extraction and purification. The choice of lysis buffer significantly impacted the amount of recovered mineral-bound DNA and facilitated selective desorption of DNA fragments. High molarity EDTA and phosphate lysis buffers recovered on average an order of magnitude more DNA from clay than other tested buffers, while both isolation approaches recovered comparable amounts of DNA. However, organic extraction caused an inhibitory effect in subsequent downstream applications (e.g., PCR), across all assessed sediment DNA extracts while silica magnetic beads induced inhibition only in half of the tested DNA extracts. Furthermore, we demonstrate that both, the isolation approach and the lysis buffer play a decisive role in successful library preparation and that lysis buffer choice impacted the final library fragment distribution. With this study, we underscore the critical importance of lysis buffer selection to maximize the recovery of mineral-bound DNA in sedimentary DNA extractions and show its profound impact on recovered fragment lengths, a crucial factor alongside existing isolation approaches in facilitating high-quality DNA extracts for downstream analysis related to ancient environmental (aeDNA) research.

molecular biology↗

bioRxiv2020

Contrasting responses of protistan plant parasites and phagotrophs to ecosystems, land management and soil properties

Functional traits are increasingly used in ecology to link the structure of microbial communities to ecosystem processes. We investigated two important protistan lineages, Cercozoa and Endomyxa (Rhizaria) in soil using Illumina sequencing and analysed their diversity and functional traits along with their responses to environmental factors in grassland and forest across Germany. From 600 soil samples, we obtained 2,101 Operational Taxonomy Units representing ~18 million Illumina reads (region V4, 18S rRNA gene). All major taxonomic and functional groups were present, dominated by small bacterivorous flagellates (Glissomonadida). Endomyxan plant parasites were absent from forest. In grassland, they were promoted by more intensive land use management. Grassland and forest strikingly differed in community composition. Relative abundances of bacterivores and eukaryvores were contrastingly influenced by environmental factors, indicating bottom-up regulation by food resources. These patterns provide new insights into the functional organization of soil biota and indications for a more sustainable land-use management. HighlightsO_LIProtistan plant parasites of worldwide importance (Phytomyxea) are absent from forest C_LIO_LIProtistan plant parasites are enhanced by land use intensification in grassland C_LIO_LIOpposite responses of protistan trophic guilds to environmental conditions in forest C_LIO_LIDrastic differences in protistan community composition between grassland and forest C_LI

ecology↗

bioRxiv2019

Highly diverse Asgard archaea participate in organic matter degradation in coastal sediments

Asgard is an archaeal superphylum that might hold the key to understand the origin of eukaryotes, but its diversity and ecological roles remain poorly understood. Here, we reconstructed 15 metagenomic-assembled genomes (MAGs) from coastal sediments covering most known Asgard archaea and a novel group, which is proposed as a new Asgard phylum named as the "Gerdarchaeota". Genomic analyses predict that Gerdarchaeota are facultative anaerobes in utilizing both organic and inorganic carbon. Unlike their closest relatives Heimdallarchaeota, Gerdarchaeota have genes encoding for cellulase and enzymes involving in the tetrahydromethanopterin-based Wood-Ljungdahl pathway. Transcriptomic evidence showed that all known Asgard archaea are capable of degrading organic matter, including peptides, amino acids and fatty acids, in different ecological niches in sediments. Overall, this study broadens the diversity of the mysterious Asgard archaea and provides evidence for their ecological roles in coastal sediments.

microbiology↗

bioRxiv2019

Environmental selection and spatiotemporal structure of a major group of soil protists (Rhizaria: Cercozoa) in a temperate grassland

Soil protists are increasingly appreciated as essential components of soil foodwebs; however, there is a dearth of information on the factors structuring their communities. Here we investigate the importance of different biotic and abiotic factors as key drivers of spatial and seasonal distribution of protistan communities. We conducted an intensive survey of a 10m2 grassland plot in Germany, focusing on a major group of protists, the Cercozoa. From 177 soil samples, collected from April to November, we obtained 694 Operational Taxonomy Units representing >6 million Illumina reads. All major cercozoan groups were present, dominated by the small flagellates of the Glissomonadida. We found evidence of environmental filtering structuring the cercozoan communities both spatially and seasonally. Spatial analyses indicated that communities were correlated within a range of four meters. Seasonal variations of bactevirores and bacteria, and that of omnivores after a time-lapse, suggested a dynamic prey-predator succession. The most influential edaphic properties were moisture and clay content, which differentially affected each functional group. Our study is based on an intense sampling of protists at a small scale, thus providing a detailed description of the niches occupied by different taxa/functional groups and the ecological processes involved.

ecology↗

bioRxiv2019

CO2 conversion to methane and biomass in obligate methylotrophic methanogens in marine sediments

Methyl substrates are important compounds for methanogenesis in marine sediments but diversity and carbon utilization by methylotrophic methanogenic archaea have not been clarified. Here, we demonstrate that RNA-stable isotope probing (SIP) requires 13C-labeled bicarbonate as co-substrate for identification of methylotrophic methanogens in sediment samples of the Helgoland mud area, North Sea. Using lipid-SIP, we found that methylotrophic methanogens incorporate 60 to 86% of dissolved inorganic carbon (DIC) into lipids, and thus considerably more than what can be predicted from known metabolic pathways ([~]40% contribution). In slurry experiments amended with the marine methylotroph Methanococcoides methylutens, up to 12% of methane was produced from CO2, indicating that CO2-dependent methanogenesis is an alternative methanogenic pathway and suggesting that obligate methylotrophic methanogens grow in fact mixotrophically on methyl compounds and DIC. Thus, the observed high DIC incorporation into lipds is likely linked to CO2-dependent methanogenesis, which was triggered when methane production rates were low. Since methylotrophic methanogenesis rates are much lower in marine sediments than under optimal conditions in pure culture, CO2 conversion to methane is an important but previously overlooked methanogenic process in sediments for methylotrophic methanogens.

microbiology↗