Biology subjects

Doering, T.

Publications and source records attributed to Doering, T..

4 recordsLinked to original sources

bioRxiv2026

Diverse H2O2-scavenging phenotypes of coral-associated bacteria reveal candidates for bleaching mitigation

There is growing interest in manipulating coral-associated bacteria to enhance coral thermal bleaching tolerance. Reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2), are major drivers of coral bleaching, therefore, coral-associated bacteria capable of scavenging H2O2 may help reduce bleaching. Bacterial candidates are commonly selected through genome inference and occasionally phenotypic assays, but how well these approaches predict H2O2-scavenging capacity is unknown. We screened 29 bacterial strains isolated from the scleractinian corals Acropora loripes and Galaxea fascicularis for genome-inferred H2O2-scavenging pathways and in vitro activity using an ABTS radical-scavenging assay, H2O2 tolerance (the highest H2O2 concentration that allows bacterial growth), H2O2 removal from the medium, and qualitative catalase activity. Although all strains encoded at least two complete H2O2-scavenging pathways, genomic prediction did not consistently align with in vitro scavenging activity. Growth under H2O2 exposure was strongly coupled with H2O2 scavenging, but these traits showed no correlation with ABTS inhibition or catalase activity inferred from bubble formation. The top-ranked phenotypes, based on H2O2 tolerance and scavenging, were observed in Roseovarius, Roseibium, Ruegeria, and Muricauda strains, which tolerated 5-50 mM H2O2. These genera are common associates of microalgae, including coral endosymbionts, which are key sources of excess ROS during thermal stress. Among these, Roseovarius and Muricauda also showed high ABTS inhibition (>97%), indicating broader antioxidant capacity that may be advantageous within the complex oxidative environment of thermally stressed corals. Strains combining strong H2O2 scavenging with broad antioxidant activity may therefore represent the most promising candidates for subsequent validation within the coral holobiont.

microbiology↗

bioRxiv2025

Polymorphic α-Glucans as Structural Scaffolds in Cryptococcus Cell Walls for Chitin, Capsule, and Melanin: Insights from 13C and 1H Solid-State NMR

Cryptococcus species are major fungal pathogens responsible for life-threatening infections in approximately a million individuals globally each year, with alarmingly high mortality rates. These fungi are distinguished by a distinctive cell wall architecture further reinforced by two virulence-associated layers, melanin and capsule, rendering them insensitive to antifungal agents targeting the cell wall, such as echinocandins. The molecular interplay between these three biomolecular layers remains poorly understood. Here we employ solid-state NMR spectroscopy to examine intact cells of both wild-type and capsule-deficient strains of C. neoformans, along with its melanized cells. High-resolution 13C and 1H data revealed five distinct structural forms of -1,3-glucans that play versatile roles in forming the rigid cell wall scaffold by interacting with chitin microfibrils and chitosan, and in stabilizing the mobile matrix by associating with {beta}-1,6-glucan and a small fraction of {beta}-1,3-glucan. Two primary forms of -1,3-glucans were distributed throughout the cell wall, hosting melanin deposition in the inner domain and capsule attachment on the cell surface. These findings offer a paradigm shift in understanding the cryptococcal cell wall and its interaction with two key virulence factors on opposite sides, raising critical biochemical questions that could inform the development of more effective antifungal treatments for cryptococcosis.

biochemistry↗

bioRxiv2023

Natural thermal stress-hardening of corals through cold temperature pulses in the Thai Andaman Sea

Thermal variability can render corals stress resistant through a phenomenon coined as "stress-hardening induced by environmental priming". Fluctuations that involve high temperature peaks have been commonly investigated, however, the effects of a stress-hardening stimulus generated by cold-water pulses has rarely been studied. Offshore island reefs in the Andaman Sea offer an ideal natural setting to study these effects, as cooling water of internal waves induce strong variability with peak intensity in January to June and absence in August to November. While western island shores are exposed to this stimulus, eastern shores remain sheltered. This study examined (1) whether corals from exposed reefs were more heat stress resistant compared to stimulus-sheltered conspecifics and (2) whether this trait can last in the absence of the stimulus. We quantified the thermal stress resistance in two ecologically important coral species, Pocillopora sp. and Porites sp., from the two island shores, during the two seasons. Coral bleaching intensity and photosynthetic efficiency of algal symbionts were measured as response variables after a short-term heat stress assay (24-48 h, 34 {degrees}C) to assess thermal stress resistance. Stress responses of all stimulus-exposed corals were either undetectable (during the season of stimulus presence) or very weak (during stimulus absence), while corals from the stimulus-sheltered shore responded strongly to heat stress irrespective of the season. Hence, thermal resistance was overall greater in corals originating from the stimulus-exposed shore, but it was slightly diminished during the season of stimulus absence, emphasizing the relevance of stimulus recurrence in maintaining the resistance trait. We exemplify that the stimulus of fluctuating low temperature pulses successfully induced stress-hardening in corals. This suggests that priming stimuli do not necessarily need to transgress certain upper thermal thresholds, but can also touch on lower thresholds to be effective. Even more, we argue that cooling pulses might represent a safer stress-hardening regime, since warming-stress accumulation can be avoided. More research is required to obtain a better understanding of environmental priming, but current findings should encourage the development of artificial stress-hardening approaches to enhance coral resistance in reef restoration efforts.

ecology↗

bioRxiv2019

Natural selection towards wild-type in composite cross populations of winter wheat

Most of our crops are grown in monoculture with single genotypes grown over wide acreage. An alternative approach, where segregating populations are used as crops is an exciting possibility, but outcomes of natural selection upon this type of crop are not well understood. We tracked allelic frequency changes in evolving composite cross populations (CCPs) of wheat grown over ten generations under organic and conventional farming. At three generations, each population was genotyped with 19 SSR and 8 SNP markers. The latter were diagnostic for major functional genes. Gene diversity was constant at SSR markers but decreased over time for genic markers. Population differentiation between the four locations could not be detected, suggesting that organic vs. non-organic crop management did not drive allele frequency changes. However, we did see changes for genes controlling plant height and phenology in all populations independently and consistently. We interpret these changes as the result of a consistent natural selection towards wild-type. Independent selection for alleles that are associated with plant height suggests that competition for light was central, resulting in the predominance of stronger intraspecific competitors, and highlighting a potential trade-off between individual and population performance.

genetics↗