Luis Ortiz-Rodriguez

Stress-Driven Reprogramming of Bacterial Biomolecular Condensates

Abstract:

Bacteria must rapidly reorganize cellular resources to survive changing environments, yet how they dynamically control the fate of their mRNAs during these transitions remains poorly understood. In this talk, I will show how bacterial ribonucleoprotein bodies (BR-bodies), biomolecular condensates involved in RNA metabolism, undergo a physical and functional transformation that allows cells to switch between mRNA degradation and storage.

Using single-molecule and ensemble fluorescence microscopy together with biochemical and quantitative approaches, we find that BR-bodies are dynamic and liquid-like during exponential growth, where they facilitate efficient mRNA degradation. Upon entry into stationary phase, however, BR-bodies become more rigid, exhibiting reduced internal dynamics, increased molecular density, and prolonged residence of the endoribonuclease RNase E. This physical transition is accompanied by a functional switch: rather than serving primarily as sites of RNA degradation, stationary-phase BR-bodies retain mRNAs and act as reservoirs for transcripts that can be reused when favorable growth conditions return.

By perturbing cellular ATP levels and translation, we further identify the accumulation of ribosome-depleted mRNA as an important driver of BR-body rigidification, with time-dependent condensate maturation reinforcing this transition. Remarkably, nutrient replenishment reverses the process: stationary-phase BR-bodies disassemble and stored mRNAs become available for rapid translation during growth recovery.

Together, these results reveal that the material properties of a biomolecular condensate are directly coupled to its biological function. More broadly, they suggest that bacteria can reversibly tune the physical state of intracellular compartments to control whether cellular resources are consumed, protected, or redeployed in response to environmental change.

Speaker: Luis Ortiz-Rodriguez, UMD Department of Chemistry and Biochemistry

The Ortiz-Rodríguez Lab aims to understand how RNA molecules are organized, transported, translated, stored, and degraded inside living bacterial cells. Although the major steps of gene expression are well established, we still know surprisingly little about how individual mRNAs navigate the crowded and highly organized bacterial cytoplasm or how their spatial organization influences their fate. Our lab combines single-molecule tracking, super-resolution fluorescence microscopy, bacterial genetics, and quantitative biophysical analysis to directly observe these processes in living cells.

A major focus of our research is following individual mRNA molecules from their sites of transcription and determining how their motion and interactions change as they transition between translation, storage, and degradation. We are particularly interested in how bacterial biomolecular condensates, including BR-bodies, organize RNA metabolism and how their physical properties influence cellular responses to changing environmental conditions. By developing new imaging and analysis approaches that connect molecular dynamics with cellular function, the Ortiz-Rodríguez Lab seeks to uncover the physical principles that govern RNA organization and gene regulation in bacteria. Ultimately, our work will provide a quantitative framework for understanding how cells control the life cycle of RNA and how spatial organization contributes to bacterial physiology and adaptation.​

Luis Ortiz-Rodríguez is an Assistant Professor in the Department of Chemistry and Biochemistry at the University of Maryland, College Park. His research combines single-molecule fluorescence microscopy, quantitative imaging, and biophysical approaches to understand how bacteria spatially organize biochemical processes and adapt to environmental stress. A major focus of his laboratory is understanding the physical properties and biological functions of bacterial biomolecular condensates, as well as how the organization and dynamics of RNA, ribosomes, and other macromolecules influence cellular physiology. He earned his Ph.D. in Chemistry from Case Western Reserve University and completed postdoctoral training at the University of Michigan, where he studied bacterial condensates using super-resolution and single-particle tracking microscopy.

Host: Jeffery Klauda

Seminars start at 4:00 pm, and refreshments will be served at 3:45 pm. All seminars are held in the 2136 Physical Sciences Complex (#415) unless otherwise noted.