Robles, V. | Search bioRxiv

bioRxiv2026

Interspecies synergism and antagonism induce differential and potentially exploitable susceptibility to various classes of antibiotics in a wound-like polymicrobial community

Chronic wounds are persistent and difficult to treat. Often this is because they are colonized by polymicrobial communities which contribute to changes in antimicrobial susceptibilities, making these infections harder to effectively clear. We explored the role a community can play in individual members survival when challenged by antibiotics, specifically looking at a community consisting of Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Acinetobacter baumannii. Our data shows that communities can contribute to both increases and decreases in susceptibilities depending on the species and the antibiotic. The changes in susceptibilities can be due to interspecies cooperation or competition, with identifiable mechanisms. We also demonstrated that current antimicrobial susceptibility testing (AST) methods used in hospitals, which focus on determining the minimum inhibitory concentration (MIC) via determination of visible turbidity breakpoints, are not able to truly indicate the clearance of bacteria, as species can persist in higher antibiotic concentrations after visible turbidity is gone. To combat decreases in antibiotic susceptibilities contributed to by the community, we used our data from individual antibiotics to determine a potentially effective antibiotic combination, similar to combinatorial therapy used in hospitals to treat recalcitrant infections. Our data proved useful, as the combination of gentamicin and cephalexin was able to overcome polymicrobial synergism and clear the desired bacteria. This demonstrates that it is possible to determine effective antibiotic treatments for polymicrobial infections, whether they be combinatorial in nature or not. One simply must account for the role of the community in order to prescribe the most effective treatment.

microbiology↗

bioRxiv2023

Drivers of plant diversity, community composition, functional traits and soil processes along an alpine gradient in the central Chilean Andes

High alpine regions are threatened but understudied ecosystems that harbor diverse endemic species, making them an important biome in which to test the role of environmental factors in driving functional trait-mediated community assembly processes. In a high mountain system in the central Chilean Andes, we tested hypotheses about the drivers of plant community diversity, functional composition and soil processes along an elevation gradient. We surveyed vegetation and spectroscopic reflectance (400-2400 nm) to quantify taxonomic, phylogenetic, functional, and spectral diversity at five sites from 2400 m to 3500 m elevation. We characterized soil attributes and processes by measuring water content, carbon and nitrogen, and net nitrogen mineralization rates. At high elevation, colder temperatures led to a reduction in available soil nitrogen, while at warmer, lower elevations, soil moisture was lower. Metrics of taxonomic, functional, and spectral alpha diversity peaked at mid-elevations, while phylogenetic species richness was highest at low elevation. Leaf nitrogen followed global patterns of increasing leaf nitrogen with colder temperatures, a pattern consistent at the community level as well as within individual species. The increase in leaf nitrogen, coupled with shifts in taxonomic and functional diversity associated with turnover in lineages, indicate that the ability to acquire and retain nitrogen in colder temperatures may be important in plant community assembly in this range. Such environmental filters have important implications for forecasting shifts in alpine plant communities under a warming climate.

ecology↗