Biology subjects

Walter, R.

Publications and source records attributed to Walter, R..

4 recordsLinked to original sources

bioRxiv2026

A microbial seedbank from a natural oil seep accelerates hydrocarbon degradation in freshwater oil spills

Anthropogenic oil spills are a major source of hydrocarbon pollution, yet freshwater oil spills are studied less than marine once. We hypothesize that microorganisms from freshwater natural oil seeps are adapted to use oil as carbon source and could serve as a seedbank to accelerate degradation of anthropogenic oil spills. To test this, microcosms were set up using water and oil from a natural oil seep in Germany, while light oil and oil naive river water simulated an anthropogenic spill. Seven conditions combined different water types (adapted, naive) and oil types (heavy, light, mixed). Oil degradation was monitored over 81 days via reverse stable isotope labeling, and pH and microbial communities were analyzed by 16S rRNA gene amplicon sequencing at the start and end. Microcosms with adapted microbes exhibited higher oil mineralization rates. In mixed-oil incubations, simulating the application of a microbial seedbank, degradation rates were 0.26 mM/day with adapted microbes versus 0.15 mM/day in naive water. Applying seep-derived microbes to naive light-oil microcosms increased hydrocarbon mineralization by 32%. These results suggest that leveraging natural microbial seedbanks could accelerate oil weathering and reduce the environmental impact of freshwater oil spills, offering a promising strategy for spill mitigation if applied safely. ImportanceFreshwater oil spills remain poorly studied despite their substantial contribution to global hydrocarbon pollution. This study demonstrates that microbial communities from freshwater natural oil seeps are pre-adapted to degrade crude oil and can significantly enhance the breakdown of anthropogenic oil spills. Applying such microbial seedbanks increased hydrocarbon mineralization by over 30%, highlighting their potential as an effective and environmentally relevant tool for oil spill mitigation. These findings support the development of nature-based strategies to accelerate oil weathering and reduce the environmental impact of freshwater oil spills.

microbiology↗

bioRxiv2025

Tissue- and temperature-dependent expression, enzyme activity, and RNAi knockdown of Catalase in a freeze-tolerant insect

Organisms that overwinter in temperate climates may experience freezing and freezing-induced oxidative stress during winter. While many insect species can survive freezing, molecular tools such as RNA interference (RNAi) or CRISPR have not been used to understand the physiological mechanisms underlying freeze tolerance. The spring field cricket Gryllus veletis can survive freezing following a 6-week fall-like acclimation. We used RNAi of an antioxidant enzyme in G. veletis to test the hypothesis that minimizing oxidative stress is important for freeze tolerance. In fat body tissue, Catalase mRNA abundance and enzyme activity increased during the acclimation that induces freeze tolerance. Other tissues such as midgut and Malpighian tubules had more stable or lower Catalase expression and activity during acclimation. In unacclimated (freeze-intolerant) crickets, RNA interference (RNAi) effectively knocked down production of the Catalase mRNA and protein in fat body and midgut, but not Malpighian tubules. In acclimated (freeze-tolerant) crickets, RNAi efficacy was temperature-dependent, functioning well at warm (c. 22{degrees}C) but not cool (15{degrees}C or lower) temperatures. This highlights a challenge of using RNAi in cold-acclimated organisms, as they may need to be warmed up for RNAi to work, potentially affecting their stress physiology. Knockdown of Catalase via RNAi in acclimated crickets also had no effect on the ability of the crickets to survive a mild freeze treatment, suggesting that Catalase may not be necessary for freeze tolerance. Our study is the first to demonstrate that RNAi is possible in a freeze-tolerant insect, but further research is needed to examine whether other genes and antioxidant molecules are important in freeze tolerance of G. veletis. HighlightsO_LICatalase expression and activity are elevated in freeze-tolerant cricket fat body C_LIO_LIRNAi knocks down Catalase in fat body and midgut at a warm temperature (22{degrees}C) C_LIO_LIRNAi is not effective at a cool temperature (15{degrees}C) that preserves freeze tolerance C_LIO_LICatalase knockdown has no impact on survival of a mild freeze treatment C_LIO_LIThe role of antioxidants in freeze tolerance warrants further study C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/637938v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1c4d9b8org.highwire.dtl.DTLVardef@b1c304org.highwire.dtl.DTLVardef@7a421eorg.highwire.dtl.DTLVardef@8af62f_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Postglacial recolonization of the Southern Ocean by elephant seals occurred from multiple glacial refugia

The Southern Ocean is warming more rapidly than other parts of our planet. How this regions endemic biodiversity will respond to such changes can be illuminated by studying past events, through genetic analyses of time-series data sets including historic and fossil remains. Archaeological and subfossil remains show that the southern elephant seal (Mirounga leonina) was common along the coasts of Australia and New Zealand in the recent past. This species is now mostly confined to sub-Antarctic islands and the southern tip of South America. We analysed ancient seal samples from Australia (Tasmania), New Zealand, and the Antarctic mainland to examine how southern elephant seals have responded to a changing climate and anthropogenic pressures during the Holocene. Our analyses show that these seals formed part of a broader Australasian lineage, comprising seals from all sampled locations from the south Pacific sector of the Southern Ocean. Our study demonstrates that southern elephant seal populations have dynamically altered both range and population sizes under climatic and human pressures, over surprisingly short evolutionary timeframes for such a large, long-lived mammal. Significance StatementGenetic data, alongside historic, archaeological, and subfossil remains show that Australasian populations of the southern elephant seal have been shaped by range expansions and contractions following the Last Glacial Maximum, with subsequent contractions during the late Holocene. These expansion and contraction events are likely to have been a direct result of climate change-induced habitat expansion and contraction, along with Indigenous and European sealing. Prehistoric climate change and more recent human pressures have substantially altered the geographic distribution and population size of southern elephant seals over short evolutionary timescales.

ecology↗

bioRxiv2020

The developmental and genetic architecture of the sexually selected male ornament of swordtails

Sexual selection results in sex-specific characters like the conspicuously pigmented extension of the ventral tip of the caudal fin - the "sword" - in males of several species of Xiphophorus fishes. To uncover the genetic architecture underlying sword formation and to identify genes that are associated with its development, we characterized the sword transcriptional profile and combined it with genetic mapping approaches. Results showed that the male ornament of swordtails develops from a sexually non-dimorphic prepattern of transcription factors in the caudal fin. Among genes that constitute the exclusive sword transcriptome only two are located in the genomic region associated with this trait; the chaperone, fkbp9, and the potassium channel, kcnh8 that in addition to its neural function performs a role known to affect fin growth. This indicates that during evolution of swordtails a brain gene has been recruited for an additional function in establishing a male ornament.

evolutionary biology↗