When they perceive a source of stress, bacteria spring into action, inducing changes in the expression of certain genes and their physiological properties to make them less vulnerable to the detected lethal substance. They also produce small ’alarmone’ proteins 3 on their surface in order to contact and activate random neighbouring bacteria. Unstressed bacteria can only change state in the presence of a sufficient amount of alarmones. Thus, only a source of stress perceived by sufficient bacteria can trigger propagation of this activation 4 .
The mechanism offers several advantages: it limits the unnecessary use of energy and enables a rapid and coordinated response in the population. Because activation is gradual, it creates diversity in the population over time, thus increasing the bacteria’s chances of survival.
These findings, published on 10 July in Nature Communications, were established using a dozen different families of antibiotics on populations of Streptococcus pneumoniae, the bacteria that causes pneumococcal infections.
2 Working at the Laboratoire de microbiologie et de génétique moléculaires (CNRS/ Université Toulouse III-Paul Sabatier) 4 This prevents the mechanism from being triggered when the source of stress only affects a single bacterial cell. Activation due to an internal source of stress that is unique to a cell, for example, does not trigger the mechanism.
Pneumococcal competence is a populational health sensor driving multilevel heterogeneity in response to antibiotics. Marc Prudhomme, Calum H. G. Johnston, Anne-Lise Soulet, Anne Boyeldieu, David De Lemos, Nathalie Campo and Patrice Polard. Nature communications, 10 July 2024.