Biology subjects

Kelbrick, M.

Publications and source records attributed to Kelbrick, M..

3 recordsLinked to original sources

bioRxiv2026

Fungicide drives de novo evolution of multidrug resistance in the plant growth promoting rhizobacterium, Pseudomonas fluorescens

Plant growth-promoting rhizobacteria (PGPR) are key members of soil microbial communities, supporting nutrient cycling, plant health, and productivity. In agricultural soils, these beneficial bacteria are often exposed to multiple stressors simultaneously, including fungicides, antibiotics, and rising temperatures. Despite their ecological importance, little is known about how PGPR respond evolutionarily to such combined stressors. Here, we investigated how the model PGPR Pseudomonas fluorescens SBW25 evolves resistance to the fungicide formulation Fubol Gold (metalaxyl-M + mancozeb), under ambient or warming soil conditions. Using a 16-week experimental evolution in soil microcosms with a fully factorial design (fungicide {+/-} warming), we assessed the evolution of fungicide resistance via phenotypic assays and whole-genome sequencing. Fungicide exposure rapidly selected for increased fungicide resistance, detectable as early as week 4, and co-selected for multidrug resistance, likely through mutations in a mexS ortholog that cause efflux pump overexpression. Warming did not alter the evolution of fungicide resistance; however, populations subjected to both fungicide and warming stress went extinct more rapidly, indicating that population evolutionary rescue was less effective under dual stress. Our findings show that fungicides alone can drive multidrug resistance in beneficial soil bacteria, suggesting that strategies to tackle AMR in agriculture should also consider non-antibiotic drivers of resistance.

microbiology↗

bioRxiv2026

Fungicide and warming interact to reduce soil ecosystem functioning

Soil microbial communities are essential to the functioning of their ecosystems, providing vital services such as plant growth promotion and bioremediation. However, intensively managed environments such as agricultural soils are increasingly challenged with multiple harsh environmental stressors from the compounding effects of climate change and conventional agricultural practices. Understanding how soil communities will respond to environmental stress along multiple axes is key for predicting how environmental change will impact terrestrial soil ecosystems. We combine experimental evolution with community phenotyping, 16s rRNA metabarcoding, fungicide resistance assays and plant experiments, to show that fungicide and warming temperatures together drive a synergistic reduction in soil community respiration rates, metabolic capacity and plant growth promotion (Hordeum vulgare), which would have been missed by looking at stressor effects independently. Dual stressors caused widespread loss of metabolic activity, particularly for carbohydrates and carboxylic acids, highlighting impairment of community function. Fungicide-evolved soil isolates had a 16-fold increase in fungicide resistance, but only in the absence of warming - suggesting that the dual stressor treatment constrained fungicide adaptation. Together, our findings suggest that the number of stressors (rather than the nuances of individual stressors) may be key for predicting soil microbial community responses to environmental change across multiple axes.

ecology↗

bioRxiv2023

Spatial refuges and nutrient acquisition predict the outcome of evolutionary rescue in evolving microbial populations

Microbial populations are often exposed to environmental stressors that impact their survival and evolution. Eco-evolutionary theory suggests microbial populations may be able to survive a stressor through "spatial refuges" - i.e., areas of low or reduced stress such as within biofilms. However, spatial refuges reduce a populations access to nutrients, so may be detrimental depending on the severity of the stressor they are sheltering from. Using predictions from a general mathematical model, and the experimental evolution of the bacterium Pseudomonas fluorescens SBW25 under salinity stress and varying opportunities to form spatial refuges (i.e., agitated or non-agitated culture conditions), we show that spatial refuges can rescue a population from stressors only when nutrient levels are high. In the surviving high-salinity evolved populations (i.e., non-agitated culture conditions and high-nutrients), clones had an increased salinity resistance, indicating that spatial refuges can facilitate evolutionary rescue. Though whole genome resequencing did not reveal a single specific mutation associated with salt resistance, we found that clones evolved under control conditions (lower salt, high-nutrients, and no agitation) acquired mutations in a putative chemotaxis gene and showed increased motility. This indicates that spatial refuges under high salinity may also constrain adaptations to other environmental factors. Together, our combination of theory, laboratory experiment, and genome re-sequencing demonstrate the value and limits of spatial refuges in alleviating environmental stress within microbial populations.

microbiology↗