Paz, B. | bioRxiv Science

bioRxiv2025

Showcasing the Rhizosphere of Medicago Polymorpha Ability to Produce Biofuels, Fix Nitrogen, and Demonstrate Similarities to Native Plant Species During a Drought Season

Acknowledging the impact of environmental change on microbial communities, provided the distinct rationale to the role of a plants capabilities within its underground network of life. Wildfires are associated with a significant decrease in microbial enzymatic activity within days, yet the long-term effects remain understudied. By focusing on microbial modifications, influenced by drought and shifts in community and functional profiles, this study contributes to understanding relationships in plant species. This study investigated the microbial composition and functional characteristics of the bacteria isolated from the rhizosphere of Medicago polymorpha during the wildfire season at Sage Hill. It aimed to assess alterations in microbial life post-drought, honing on Actinobacteria, Proteobacteria, and Firmicutes, the most abundant and climate-tolerant phyla. Key results showed bacterial isolates capable of cycling biofuels and nitrogen, surprisingly resembling native species more than invasive, and showing similarities to the past wet season than to the current arid one. Statistical analysis revealed significantly different bacterial abundances and identities compared to the plants present within the same season, highlighting Actinobacteria and Proteobacteria as highly responsive to climate changes. Further analysis showed greater similarities to native species despite Medicago polymorphas invasiveness. Over half of the microorganisms hydrolyzed their environment and produced biofuels. One-third generated siderophores and 60% demonstrated nitrogen fixation. The results emphasize the understanding of microbial shifts that occur in plant species, using the new soil site of Medicago polymorpha as a model of how arid ecosystems inform agricultural development. These findings support microbial resilience and provide strategic agriculture in drought-prone environments.

microbiology↗

bioRxiv2024

An opioid efficacy switch for reversible optical control of peripheral analgesia

The mu-opioid receptor (MOR) is a major target for the treatment of pain. However, opioids are prone to side effects which limit their effectiveness as analgesics and can lead to opioid use disorders or, even, lethal overdose. The systemic administration of opioid agonists makes it both very difficult to decipher their underlying circuit mechanisms of action and to limit drug action to specific receptor subpopulations to isolate therapeutic effects from adverse side effects. Here we design, synthesize, and characterize a reversibly photoswitchable morphinan agonist termed "azo-morphine-3" (AM-3) which interconverts from low to high efficacy in response to different wavelengths of light to enable optical control of MOR signaling. Cryo-EM structures of the low efficacy "trans" and high efficacy "cis" states of AM-3 bound to the MOR reveal distinct binding modes of the photoswitchable azobenzene moiety, each inducing unique structural dynamics, providing insight into the molecular basis of agonist efficacy. In mice, AM-3 drives reversible and repeatable optical control of anti-nociception with a reduced side effect profile owing to its restriction to the periphery and its ability to be locally activated at the site of pain.

pharmacology and toxicology↗