Sundar, G. | bioRxiv Science

bioRxiv2022

Efflux pump gene amplifications bypass necessity of multiple target mutations for resistance against dual-targeting antibiotic

The rise of antimicrobial resistance has motivated the development of antibiotics that have multiple cellular targets, to theoretically reduce the frequency of resistance evolution, but adaptive trajectories and genetic determinants of resistance against such antibiotics are understudied. Here we investigate these in methicillin resistant Staphylococcus aureus (MRSA) using experimental evolution of ten independent populations in the presence of delafloxacin (DLX), a novel fluoroquinolone that targets both DNA gyrase and topoisomerase IV. We show that coding sequence mutations and genomic amplifications of the gene encoding a poorly characterized efflux pump, SdrM, lead to the evolution of high DLX resistance, circumventing the requirement for mutations in the target enzymes. Almost all of our evolved populations had one of two SdrM coding sequence mutations, which led to moderate DLX resistance. Additionally, these populations had 13 distinct genomic amplifications, each containing sdrM and two adjacent genes encoding efflux pumps, which resulted in up to 100-fold higher DLX resistance. While increased sdrM expression provided the selective advantage of the amplification in the DLX evolution, the adjacent efflux pumps hitchhiking in the genomic amplification contributed to cross-resistance against the aminoglycoside streptomycin. Finally, lack of sdrM necessitated mutations in both DNA gyrase and topoisomerase IV to evolve DLX resistance, and the presence of sdrM thus increased the frequency of resistance evolution. Our study highlights that instead of reduced rates of resistance, evolution of resistance to antibiotics with multiple cellular targets can involve alternate high-frequency evolutionary paths such as genomic amplifications of efflux pumps, that may cause unexpected alterations of the fitness landscape, including antibiotic cross-resistance.

microbiology↗

bioRxiv2020

Embodied virtual reality for the study of real-world motor learning

Motor-learning literature focuses on simple laboratory-tasks due to their controlled manner and the ease to apply manipulations to induce learning and adaptation. Recently, we introduced a billiards paradigm and demonstrated the feasibility of real-world-neuroscience using wearables for naturalistic full-body motion-tracking and mobile-brain-imaging. Here we developed an embodied virtual-reality (VR) environment to our real-world billiards paradigm, which allows to control the visual feedback for this complex real-world task, while maintaining sense of embodiment. The setup was validated by comparing real-world ball trajectories with the trajectories of the virtual balls, calculated by the physics engine. We then ran our learning protocol in the embodied VR. Subjects played billiard shots when they held the physical cue and hit a physical ball on the table while seeing it all in VR. We found comparable learning trends in the embodied VR to those we previously reported in the physical real-world task. Embodied VR can be used for learning real-world tasks in a highly controlled environment which enables applying visual manipulations, common in laboratory-tasks and rehabilitation, to a real-world full-body task. Embodied VR enables to manipulate feedback and apply perturbations to isolate and assess interactions between specific motor-learning components, thus enabling addressing the current questions of motor-learning in real-world tasks. Such a setup can be used for rehabilitation, where VR is gaining popularity but the transfer to the real-world is currently limited, presumably, due to the lack of embodiment.

neuroscience↗