Under stress, bacterial RNA and proteins tell different stories
During infection, bacteria encounter rapidly changing and stressful environments inside the body. To understand how they adapt, researchers often measure messenger RNA (mRNA), which carries information from genes that can be translated into proteins. While mRNA levels are widely used to monitor bacterial responses, proteins carry out much of the work inside the cell and are influenced by…
During bacterial infection, researchers typically analyze messenger RNA (mRNA) to monitor how cells respond, as mRNA carries genetic information that translates into proteins. However, scientists have struggled to determine if mRNA levels accurately predict protein abundance, especially under stress. To address this, researchers examined three human pathogens—Salmonella enterica Typhimurium, Yersinia pseudotuberculosis, and Staphylococcus aureus—by subjecting them to 10 stress conditions common in infection environments.
While overall trends between mRNA and protein levels were similar across species, the relationship weakened significantly under high-stress conditions. Sena Gizem Süer, a doctoral student involved in the study, explained that bacteria rapidly alter their cellular plans in response to stress, changing messages faster than they can produce proteins.
Under osmotic stress, which occurs when dissolved substances disrupt a cell's water balance, there was a particularly weak match between mRNA and protein levels across all three bacteria. Computational analyses and lab experiments suggested that translation—the process by which ribosomes read mRNA to build proteins—slowed under osmotic stress in Yersinia and Salmonella, despite continued translation.
However, the exact cause of this slowdown remains unclear, with possible explanations including effects on the cell envelope and molecule transport. Kemal Avican, the senior author, emphasized the need to better understand the uncertainty in the mRNA-protein relationship, particularly under stress during infection. The team aims to extend their research to other stress conditions to ultimately predict bacterial protein levels during infection, a goal currently unachievable with proteomics alone.
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