A collaboration between Dr. Mark Mandel and Dr. Andrew Mehle of the Department of Medical Microbiology & Immunology (MMI) has uncovered a novel type of bacterial RNA-binding protein, revealing an unusual mechanism of bacterial gene regulation.

In their recent paper, “RtmR is a membrane-embedded RRM family RNA-binding protein,” the researchers characterized RtmR, a protein found in the marine bacterium Vibrio fischeri. RtmR has two particularly unusual features: it is embedded in the bacterial cell membrane, an uncommon arrangement for an RNA-binding protein, and it contains an RNA recognition motif (RRM), a protein domain more commonly found in eukaryotes. The team demonstrated that RtmR binds RNA and regulates the expression of genes involved in biofilm formation, an important process in the establishment of the beneficial symbiosis between V. fischeri and the Hawaiian bobtail squid.

This discovery brings together the complementary expertise of two MMI research groups. Dr. Mandel’s laboratory focuses on bacterial signal transduction and the molecular mechanisms underlying interactions between animals and their natural microbial partners. His research uses the V. fischeri–Hawaiian bobtail squid symbiosis to understand how bacteria communicate with and selectively colonize animal hosts. Through bacterial genetics and imaging, his group investigates how these partners establish a specific and reproducible relationship.

Dr. Mehle’s laboratory specializes in RNA-binding factors, particularly those involved in viral infection. His research focuses on influenza virus polymerase, a central component of viral replication that interacts with viral RNA and proteins to direct the production and replication of the viral genome. His group investigates how these interactions influence viral replication, pathogenicity, and transmission between species.

By combining expertise in bacterial signaling and RNA-binding proteins, the Mandel and Mehle laboratories were uniquely positioned to characterize this unusual bacterial protein. Their findings expand our understanding of bacterial RNA regulation and highlight the value of interdisciplinary collaboration within MMI in advancing discoveries at the intersection of microbiology and molecular biology.