Biology subjects

Maggs-Kölling, G.

Publications and source records attributed to Maggs-Kölling, G..

5 recordsLinked to original sources

bioRxiv2026

Trace gas oxidation supports sub-surface microbial communities across Namib Desert fog and aridity gradients

Widely accepted climate predictions indicate that drylands will expand to cover more than half of the Earths terrestrial surface by the end of the 21st century. In these environments, harsh conditions including nutrient and water limitations restrict plant and animal life, thereby increasing the importance of soil microbial communities in nutrient cycling and ecosystem functioning. The Namib Desert is a distinctive dryland ecosystem characterised by a steep natural aridity gradient, transitioning from a coastal hyperarid zone influenced by frequent fog deposition to an inland arid region receiving seasonal rainfall. This study investigates the impact of water availability and moisture regime on microbial trace gas oxidation and community composition across this aridity gradient. Quantitative analyses revealed that total microbial abundance and activity indicators, including ATP concentrations and respiration rates, were significantly (p < 0.005) reduced in hyperarid soils compared to their arid counterparts. In contrast, hyperarid fog-dominated soils exhibited significantly (p < 0.0005) elevated rates of atmospheric hydrogen oxidation, even in the absence of water inputs. We propose that sustained high-affinity hydrogen oxidation, coupled with rapid microbial resuscitation following wetting events, supports shallow sub-surface microbial communities in the Namib Desert, particularly in the coastal hyperarid zone. Together, these findings challenge current understanding of the lower limits of microbial activity and reveal alternate metabolic pathways that enable microbial persistence in hyperarid hot desert soils. ImportanceDrylands are expanding globally, yet the mechanisms that allow microbial life to persist under extreme and sustained water limitation remain poorly understood. This study demonstrates that atmospheric trace gas oxidation, particularly high-affinity hydrogen oxidation, supports active and resilient microbial communities in hyperarid soils of the Namib Desert, even in the absence of liquid water inputs. By revealing how microbes may couple trace gas metabolism to energy and water generation, our findings provide new insight into the lower limits of microbial activity in dry hot desert soils and highlight the need to investigate how microbes persist and sustain soil ecosystem functioning.

microbiology↗

bioRxiv2024

Namibian fairy circles: Hostile territory for soil nematodes

Fairy circles are rings of grass with centers of bare soil that are found in some arid grasslands. Above- and belowground chemical and biological attributes of fairy circles have been explored in an ongoing debate about the ultimate causes of this pattern. We studied the soil nematode communities associated with Stipagrostis fairy circles along a 900-km range in the Namib Desert of Namibia in southern Africa. Nematode abundance and diversity were highest in soils along the vegetation rings that define fairy circles and in soils in the vegetated matrix surrounding the bare circles, demonstrating the positive impact of plant-derived resources on nematode communities. In contrast, soils from the bare centers of fairy circles had lower organic matter content and were nearly defaunated, averaging only 9.9 {+/-} 1.7 nematodes 100 g-1 soil. Bacterial-feeding Acrobeloides nematodes were the only taxa over-represented in center soils in comparison to ring soils. Our results indicate that nematode communities are influenced by the unique soil environments that the fairy circle vegetation pattern generates and suggest that the soils at the centers of fairy circles are uniquely hostile habitat for soil organisms as well as plants. Co-occurrence network analysis of nematode communities elucidated relationships among the taxa. For example, the abundances of dorylaims and Nothacrobeles were positively correlated across all soil positions, suggesting they have overlapping ecological niches. In ring soils, the abundances of fungal-feeding Aphelenchoides, Ditylenchus, and Hexatylus were positively correlated, likely due to enhanced fungal communities in these plant-influenced soils. Panagrobelus demonstrated niche specialization by being negatively correlated to two other bacterial-feeding taxa (Elaphonema in matrix soils and Acrobeloides in ring soils). The co-occurrence patterns revealed by these relatively low diversity communities provide insights into the potential roles of nematode interactions as well as environmental factors in community assembly.

ecology↗

bioRxiv2022

With a pinch of salt: metagenomic insights into Namib Desert salt pan microbial mats and halites reveal functionally adapted and competitive communities

Salt pans or playas, which are saline-rich springs surrounded by halite evaporates in arid environments, have played an essential role in landscape erosion during the formation of the Namib Desert and are numerous in its central region. In this study, we used shotgun metagenomics to investigate the phylogenetic and functional capacities of the microbial communities from two salt pans (namely, Eisefeld and Hosabes) located in the Central Namib Desert, located in Southwest Africa. We studied the source and sink sediment mat communities of the saline streams, as well as those from two halites (crystallized structures on the stream margins). The microbial assemblages and potential functions were distinct in both niches. Independently from their localization (Eisfeld vs Hosabes and source vs sink), the sediment mat communities were dominated by members of the Alpha- and Gamma-proteobacteria classes, while halites were Archaea-dominated and also contained high abundances of the extremely halophilic bacterium Salinibacter sp. (phylum Bacteroidota). Photoheterotrophy and chemoheterotrophy were the principal lifestyles in both niches, with halite communities having a reduced diversity of metabolic pathways. Intense microbial-virus interactions in both niches were implied by the widespread detection of CRISPR-Cas defense systems. We identified a putatively novel clade of type II CRISPR-Cas systems, as well as novel candidate viral lineages of the class Caudoviricetes and of Halobacteriales-infecting haloviruses. Putative gene transfer agent-like sequences within the Alphaproteobacteria were identified in the sediment mat communities. These horizontal gene transfer elements have the potential to drive genome plasticity and evolution of the Alphaproteobacteria in the Namib Desert salt pan microbiomes. ImportanceThe hyperarid Namib Desert is one of the oldest deserts on Earth. It contains multiple clusters of playas which are saline-rich springs surrounded by halite evaporites. Playas are of great ecological importance and their indigenous (poly)extremophilic microorganisms are potentially involved in the precipitation of minerals such as carbonates and sulfates and have been of great biotechnological importance. While there has been a considerable amount of microbial ecology research preformed on various Namib Desert edaphic microbiomes, little is known about the microbial communities inhabiting its multiple playas. In this work, we therefore provide a comprehensive taxonomic and functional potential characterization of the microbial, including viral, communities of sediment mats and halites from two distant Namib Desert, contributing towards a better understanding of the ecology of this biome.

microbiology↗

bioRxiv2021

Temporal dynamics of microbial transcription in wetted hyperarid desert soils

Rainfall is rare in hyperarid deserts but, when it occurs, it triggers large biological responses which are considered to be essential for the long-term maintenance of biodiversity. In such environments, microbial communities have major roles in nutrient cycling, but their functional responses to short-lived resource opportunities are poorly understood. We used whole community metatranscriptomic data to demonstrate structured and sequential functional responses in desiccated desert soils to a simulated rainfall event over a seven-day time frame. Rapid transcriptional activation of Actinobacteria, Alpha-proteobacteria and phage transcripts was followed by a marked increase in protist and myxobacterial activity, before returning to the original state. In functional terms, motility systems were activated in the early phases, whereas competition-toxicity systems increased in parallel to the activity from predators and the drying of soils. The dispersal-predation dynamic was identified as a central driver of microbial community responses to watering. Carbon fixation mechanisms that were active under dry condition were rapidly down-regulated in wetted soils, and only reactivated on a return to a near-dry state, suggesting a reciprocal balance between carbon fixation and fixed-carbon acquisition processes. Water addition induced a general reduction in the transcription of stress response genes, most prominently HSP20, indicating that this chaperone is particularly important for life in desiccated ecosystems. Based on these data, we propose a rainfall response model for desert soil microbiomes.

microbiology↗

bioRxiv2018

Nutrient acquisition, rather than stress response over diel cycles, drives microbial transcription in a dessicated Namib Desert soil

Hot desert surface soils are characterised by extremely low water activities for large parts of any annual cycle. It is widely assumed that microbial processes in such soils are very limited. Here we present the first metatranscriptomic survey of microbial community function in a low water activity hyperarid desert soil. Sequencing of total mRNA revealed a diverse and active community, dominated by Actinobacteria. Metatranscriptomic analysis of samples taken at different times over three days indicated that most functions did not fluctuate on a diel basis, except for a eukaryotic subpopulation which was induced during the cooler night hours. High levels of transcription of chemoautotrophic carbon fixation genes contrasted with limited expression of photosynthetic genes, indicating that chemoautotrophy is an important alternative to photosynthesis for carbon cycling in desiccated desert soils. Analysis of the transcriptional levels of key N-cycling genes provided strong evidence that soil nitrate was the dominant nitrogen input source. Transcriptional network analyses and taxon-resolved functional profiling suggested that nutrient acquisition processes, and not diurnal environmental variation, were the main drivers of community activity in hyperarid Namib Desert soil. While we also observed significant levels of expression of common stress response genes, these genes were not dominant hubs in the co-occurrence network.

ecology↗