Biology subjects

Totsche, K. U.

Publications and source records attributed to Totsche, K. U..

5 recordsLinked to original sources

bioRxiv2025

Balancing Act: Groundwater microbiome''s resilience and vulnerability to hydroclimatic extremes

Groundwater health is increasingly threatened by climate change, which alters precipitation patterns, leading to groundwater recharge shifts. These shifts impact subsurface microbial communities, crucial for maintaining ecosystem functions. In this decade-long study of carbonate aquifers, we analyzed 815 bacterial 16S rRNA gene datasets, 226 dissolved organic matter (DOM) profiles, 387 metabolomic datasets, and 174 seepage microbiome sequences. Our findings reveal distinct short- and long-term temporal patterns of groundwater microbiomes driven by environmental fluctuations. Microbiomes of hydrologically connected aquifers exhibit lower temporal stability due to stochastic processes and greater susceptibility to surface disturbances, yet they demonstrate remarkable resilience. Conversely, isolated aquifer microbiomes show resistance to short-term changes, governed by deterministic processes, but exhibit reduced stability under prolonged stress. Variability in seepage-associated microorganisms, DOM, and metabolic diversity further drive microbiome dynamics. These findings highlight the dual vulnerability of groundwater systems to acute and chronic pressures, emphasizing the critical need for sustainable management strategies to mitigate the impacts of hydroclimatic extremes.

microbiology↗

bioRxiv2024

Current-use and legacy contaminants evidence dissolved organic matter transfer and dynamics across a fractured-rock groundwater recharge area

Anthropogenic activities cause the release of vast amounts of contaminants into the environment which eventually reach even groundwater resources. With usually sparse regulatory monitoring of limited priority compounds, the large spectrum of contaminants, and the intricacies of intra- and inter-annual contaminant dynamics, such as the emergence and mobilisation of contaminants, are easily overlooked. Utilizing an 6-year record of untargeted LC-MS assessment of dissolved organic, we report the detection and tracing of selected environmental chemicals in the Hainich Critical Zone Exploratory (central Germany), representing a model groundwater flow system under different land use. The insect repellent DEET (N,N-diethyl-m-toluamide) and the coniferous resin acid 7-ODAA (7-oxodehydroabietic acids) show phases of seasonal dynamics in line with their expected periods of release. The legacy herbicides simazine, the triazine transformation product hydroxypropazine, and the flame retardant/plasticiser TPP (triphenyl phosphate) occurred episodically at various locations in the fractured sedimentary bedrock. Within the period of monitoring, extreme weather events (i.e., the severe 2018 drought) and extreme subsurface responses (i.e., 5-year groundwater highstand 2018) likely contributed to long-term organic matter dynamics, potentially causing re-emergence of legacy agrochemicals. This investigation points to the persistence and mobilisation of anthropogenic contaminants, and highlights the importance of long-term combined untargeted and targeted analysis of the groundwater dissolved organic matter for understanding subsurface ecosystems processes. The results add a note of caution for regulatory monitoring since also legacy contaminant levels may considerably vary over time. HighlightsO_LI6 years of monitoring with non-target LC-MS screenings; 4-weekly samplings C_LIO_LI5 current-use and legacy compounds that evidence dissolved organic matter transfer C_LIO_LICompounds comprise regularly targeted and non-monitored features in groundwater C_LIO_LIPronounced phases of non-detects help to further investigate surface-subsurface coupling C_LIO_LIThis illustrates the need for spatiotemporally highly resolved non-target monitoring C_LI

biochemistry↗

bioRxiv2023

Genome streamlining in CPR bacteria transitioning from soil to groundwater

To better understand the influence of habitat on the genetic content of Candidate Phyla Radiation (CPR) bacteria, we studied the effects of transitioning from soil to groundwater on genomic divergences of these organisms. Bacterial metagenome-assembled genomes (318 total, 35 of CPR bacteria) were generated from seepage waters and compared directly to groundwater counterparts. Seepage water CPR bacteria exhibited 1.24-fold greater mean genome size, while their inferred mean replication rate was 21.1% lower than groundwater lineages. While exploring gene loss and adaptive gains in closely related lineages in groundwater, we identified a zinc transporter, a surface protein, and a lipogylcopeptide resistance gene unique to a seepage Parcubacterium. A nitrite reductase gene unique to the groundwater Parcubacterium, likely acquired from pelagic microbes via horizontal gene transfer, was also identified. Groundwater Parcubacteria harbored nearly double the fraction (9.4%) of pseudogenes than their seepage kin (4.9%), suggesting further genome streamlining.

microbiology↗

bioRxiv2022

A glimpse of the paleome in endolithic microbial communities

The terrestrial subsurface houses a significant proportion of the Earths microbial biomass. Our understanding about terrestrial subsurface microbiomes is almost exclusively derived from groundwater and porous sediments. To obtain more insights about endolithic microbiomes and their metabolic status, we investigated rock samples from the vadose zone, fractured aquifers, and deep aquitards. Using methods from paleogenomics, we recovered sufficient DNA for metagenomics from rock specimens independent of porosity, lithology, and depth. We estimated between 2.81 and 4.25 x 105 cells x g-1 rock. DNA damage patterns revealed paleome signatures (genetic records of past microbial communities) for three rock specimens from the vadose zone. The taxonomy and functional potential of paleome communities revealed increased abundances of chemolithoautotrophs, and a broader metabolic potential for aromatic hydrocarbon breakdown. Our study suggests that limestones represent ideal archives for genetic records of past microbial communities, due to their specific conditions facilitating long-term DNA preservation.

microbiology↗

bioRxiv2021

Groundwater bacterial communities evolve over time, exhibiting oscillating similarity patterns in response to recharge

Time series analyses are a crucial tool for uncovering the patterns and processes shaping microbial communities and their functions, especially in aquatic ecosystems. Subsurface aquatic environments are perceived to be more stable than oceans and lakes, due to the lack of sunlight, the absence of photosysnthetically-driven primary production, low temperature variations, and oligotrophic conditions. However, periodic groundwater recharge should affect the structure and succession of groundwater microbiomes. To disentangle the long-term temporal changes in groundwater bacterial communities of shallow fractured bedrock community, and identify the drivers of the observed patterns, we analysed bacterial 16S rRNA gene sequencing data for samples collected monthly from three groundwater wells over a six-year period (n=230) along a hillslope recharge area. We show that the bacterial communities in the groundwater of limestone-mudstone alternations were not stable over time and showed oscillating dissimilarity patterns which corresponded to periods of groundwater recharge. Further, we observed an increase in dissimilarity over time (generalized additive model P < 0.001) indicating that the successive recharge events result in communities that are increasingly more dissimilar to the initial reference time point. The sampling period was able to explain up to 29.5% of the variability in bacterial community composition and the impact of recharge events on the groundwater microbiome was linked to the strength of the recharge and local environmental selection. Many groundwater bacteria originated from the recharge-related sources (mean = 66.5%, SD = 15.1%) and specific bacterial taxa were identified as being either enriched or repressed during recharge events. Overall, similar to surface aquatic environments, groundwater microbiomes vary through time, though we revealed groundwater recharges as unique driving factors for these patterns. The high temporal resolution employed here highlights the complex dynamics of bacterial communities in groundwater and demonstrated that successive shocks disturb the bacterial communities, leading to decreased similarity to the initial state over time.

microbiology↗