Biology subjects

Brauer, V.

Publications and source records attributed to Brauer, V..

3 recordsLinked to original sources

bioRxiv2024

Multiple stressor effects on organic carbon degradation and microbial community composition in urban river sediments in a mesocosm experiment

Microorganisms in river sediments are the primarily responsible organisms for the turnover of dissolved organic carbon (DOC) in these systems and therefore are key players for river ecosystem functioning. Rivers are increasingly threatened by multiple stressors such as salinization and temperature rise, but little is known about how microbial DOC-degradation responds to these stressors and whether this function recovers after stressor release. Here, we investigated the direct and indirect effects of salinity and temperature increase and decrease on microbial communities and their ability to degrade DOC in river sediments using the outdoor experimental mesocosm system ExStream. Composition of sediment microbial communities was determined at the end of acclimatization, stressor, and recovery phase using 16S rRNA gene sequencing. At the same time points, DOC degradation rates were quantified in additional microcosm incubations based on isotopic changes of CO2 with the help of reverse stable isotope labelling. Our results showed that raising the salinity by 154.1 mg Cl- L-1 and temperature by 3.5 {degrees}C did not affect DOC degradation during the stressor phase but significantly increased DOC degradation in the recovery phase after stressors were released. Likewise, microbial community composition stayed constant during acclimation and stressor phase, but became more diverse in the recovery phase. The results indicate that microbial community composition and functioning were resistant towards both stressors, but responded to stressor release due to indirect effects of stressor increase and release on the riverine food web. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/602289v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1074eccorg.highwire.dtl.DTLVardef@c634a1org.highwire.dtl.DTLVardef@a96182org.highwire.dtl.DTLVardef@40ae8e_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Functional characterization of clinical isolates of the opportunistic fungal pathogen Aspergillus nidulans

Aspergillus nidulans is an opportunistic fungal pathogen in patients with immunodeficiency and virulence of A. nidulans isolates has mainly been studied in the context of the chronic granulomatous disease (CGD), with characterization of clinical isolates obtained from non-CGD patients remaining elusive. This study therefore carried out a detailed biological characterization of two A. nidulans clinical isolates (CIs), obtained from a patient with breast carcinoma and pneumonia and from a patient with cystic fibrosis that underwent lung transplantation, and compared them to the reference, non-clinical A4 strain. Both CIs presented increased growth in comparison to the reference strain in the presence of physiologically-relevant carbon sources. Metabolomic analyses showed that the three strains are metabolically very different from each other in these carbon sources. Furthermore, the CIs were highly susceptible to cell wall perturbing agents but not to other physiologically-relevant stresses. Genome analyses identified several frame-shift variants in genes encoding cell wall integrity (CWI) signalling components. Significant differences in CWI signalling were confirmed by western blotting among the three strains. In vivo virulence studies using several different models revealed that strain MO80069 had significantly higher virulence in hosts with impaired neutrophil function when compared to the other strains. In summary, this study presents detailed biological characterization of two A. nidulans sensu stricto clinical isolates. Just like in A. fumigatus, strain heterogeneity exists in A. nidulans clinical strains that can define virulence traits. Further studies are required to fully characterize A. nidulans strain-specific virulence traits and pathogenicity. ImportanceImmunocompromised patients are susceptible to infections with opportunistic filamentous fungi from the genus Aspergillus. Although A. fumigatus is the main etiological agent of Aspergillus spp.-related infections, other species, such as A. nidulans are prevalent in a condition-specific manner. A. nidulans is a predominant infective agent in patients suffering from chronic granulomatous disease (CGD). A. nidulans isolates have mainly been studied in the context of CGD, although infection with A. nidulans also occurs in non-CGD patients. This study carried out a detailed biological characterization of two non-CGD A. nidulans clinical isolates and compared it to a reference strain. Phenotypic, metabolomic and genomic analyses highlight fundamental differences in carbon source utilization, stress responses and maintenance of cell wall integrity among the strains. One clinical strain had increased virulence in models with impaired neutrophil function. Just as in A. fumigatus, strain heterogeneity exists in A. nidulans clinical strains that can define virulence traits.

microbiology↗

bioRxiv2017

Trade-off shapes diversity in eco-evolutionary dynamics

We introduce an Interaction and Trade-off based Eco-Evolutionary Model (ITEEM), in which species are competing for resources in a well-mixed system, and their evolution in interaction trait space is subject to a life-history trade-off between replication rate and competitive ability. We demonstrate that the strength of the trade-off has a fundamental impact on eco-evolutionary dynamics, as it imposes four phases of diversity, including a sharp phase transition. Despite its minimalism, ITEEM produces without further ad hoc features a remarkable range of observed patterns of eco-evolutionary dynamics. Most notably we find self-organization towards structured communities with high and sustainable diversity, in which competing species form interaction cycles similar to rock-paper-scissors games.

bioinformatics↗