When Ole Schmöker peered into the molecular machinery of a little-known bacterium called Simkania negevensis, he found something striking: the pathogen was taking cues from its human host before deciding how aggressively to attack. The discovery, published in Nature Communications, reveals for the first time that bacteria can calibrate their virulence in real time based on the metabolic state of the cells they infect—a finding that could reshape how we understand and fight infections.
Simkania negevensis, a cousin of the well-known Chlamydia, can cause respiratory and pulmonary infections. Like many bacterial pathogens, it deploys specialized proteins called virulence factors to manipulate human cells, remodeling them to favor bacterial reproduction. But the Greifswald team found something unusual about one of these proteins, called SnCE1: it doesn't just act on host cells—it listens to them.
The key messenger is a molecule called Acetyl-CoA, which serves as a primary energy currency in human cells. When Acetyl-CoA levels are high, indicating the host cell is metabolically active, SnCE1 becomes more chemically modified and changes its behavior. It can both strip regulatory molecules called SUMO from host proteins and alter itself by attaching acetyl groups to certain amino acids. Remarkably, both reactions are catalyzed by the same active site on the enzyme—a dual function scientists had never documented before.
This self-modification determines whether SnCE1 stays active and where it travels within the cell. Sometimes it relocates to the mitochondria, the cell's powerhouses, and triggers their fragmentation. Exactly why the bacteria need this mitochondrial disruption remains unclear, but the pattern is unmistakable: the pathogen is dynamically adjusting its strategy based on what it finds inside the cell.
The implications extend beyond basic biology. Antimicrobial resistance is placing growing strain on hospitals worldwide, with doctors increasingly forced to switch medications or extend treatments when standard antibiotics fail. By uncovering how bacteria sense and respond to their environment inside human tissue, the Greifswald team—working across the Faculty of Mathematics and Natural Sciences, University Medicine Greifswald, and partner universities in Würzburg and Cologne—has identified a mechanism that could eventually open new therapeutic avenues.
"Our results show how important the chemical modification of proteins is for adjusting bacterial virulence factors to the host cell's metabolism," said lead author Ole Schmöker. Professor Michael Lammers, who supervised the research, noted that understanding these interactions could help scientists develop treatments that disrupt the pathogen's ability to calibrate its attack. In a world where drug-resistant infections are becoming more common, knowing exactly how bacteria fine-tune their infections gives researchers a fresh target to aim for.