Pernot, J. | bioRxiv Science

bioRxiv2025

RACLET: the Ramp Above Critical Level Endurance Test to evaluate critical force in isometric task.

The Ramp Above Critical Level Endurance Test (RACLET) is a novel submaximal test designed to evaluate the parameters of the critical force model without strenuous exercise. This study aimed to validate the RACLET in healthy and pathological populations and to assess its reliability, concurrent validity, and predictive capacity. Sixteen healthy volunteers and ten patients with respiratory pathologies participated in this study. The RACLET consisted of a decreasing ramp force starting at 60% and ending at 15% of the maximum force for a total duration of 425 s with brief regular maximal voluntary contractions. The goodness of fit for the RACLET model on the maximal contraction force was excellent in both populations (median r2{approx} 0.95). In patients, RACLET parameters demonstrated excellent reliability (ICC > 0.90). The concurrent validity of the critical force estimate compared with the all-out method was high (error: -0.3{+/-}7.4%). The models predictive capacity for time-to-exhaustion and fatigue during constant-intensity exercise was excellent (r2 = 0.910 and 0.907, respectively). The RACLET provides a reliable and valid estimate of critical force model parameters opening up numerous practical applications in vulnerable populations, individualised physical activity programs, and longitudinal monitoring. The feasibility and performance of the test make it a promising tool for assessing muscle function in various contexts.

biophysics↗

bioRxiv2025

Fighting Aspergillus infection using biocontrol bacteria: A proof-of-concept of environmental interference in a translational setting

Aspergillus fungi are opportunistic pathogens that affect millions of people worldwide. Aspergilli produce organic acids to optimize the environmental pH and match the needs of their enzymatic machinery. In this study, we tested the hypothesis that this also occurs during infection. By producing oxalic acid (OA), Aspergillus would manipulate pH during lung infection and thus, interfering with this process could control the pathogen. To test this hypothesis, we assessed in silico the potential for OA production in a wide range of Aspergilli. A genetic marker for AO production was detected in most of the species including prevalent human pathogens. We tested OA production in vitro in four strains of A. niger and A. fumigatus, but only one of the A. niger strains produced OA consistently. For this fungal strain, oxalotrophic bacteria were able to control fungal growth via OA consumption. To translate this observation into a pre-clinical system, increasingly complex experiments were performed. In 3D-cell cultures, A. niger also secreted OA and modified pH and free Ca2+. Co-inoculation of the oxalotrophic bacterium inhibited the development of the fungus. However, biocontrol could not be replicated in Galleria mellonella, which is often used as an infection model. In contrast, the bacterium improved disease score and the absence of oxalate crystals in the lungs in the mouse model. This biocontrol interaction between oxalotrophic bacteria and A. niger represents a paradigm shift in the fight against opportunistic fungal pathogens, where the goal is to render the host environment less permissive to pathogen development One Sentence SummaryDemonstration of biocontrol as a therapeutic concept to combat Aspergillus niger with oxalotrophic bacteria in an animal infection model

microbiology↗