Affiliation:
1. Department of Biochemistry and Molecular Biology, University of Texas Medical Branch Galveston, Galveston, Texas, USA
Abstract
ABSTRACT
Bacteria are capable of withstanding large changes in osmolality and cytoplasmic pH, unlike eukaryotes that tightly regulate their pH and cellular composition. Previous studies on the bacterial acid stress response described a rapid, brief acidification, followed by immediate recovery. More recent experiments with better pH probes have imaged single living cells, and we now appreciate that following acid stress, bacteria maintain an acidic cytoplasm for as long as the stress remains. This acidification enables pathogens to sense a host environment and turn on their virulence programs, for example, enabling survival and replication within acidic vacuoles. Single-cell analysis identified an intracellular pH threshold of ~6.5. Acid stress reduces the internal pH below this threshold, triggering the assembly of a type III secretion system in
Salmonella
and the secretion of virulence factors in the host. These pathways are significant because preventing intracellular acidification of
Salmonella
renders it avirulent, suggesting that acid stress pathways represent a potential therapeutic target. Although we refer to the acid stress response as singular, it is actually a complex response that involves numerous two-component signaling systems, several amino acid decarboxylation systems, as well as cellular buffering systems and electron transport chain components, among others. In a recent paper in the
Journal of Bacteriology
, M. G. Gorelik, H. Yakhnin, A. Pannuri, A. C. Walker, C. Pourciau, D. Czyz, T. Romeo, and P. Babitzke (J Bacteriol 206:e00354-23, 2024,
https://doi.org/10.1128/jb.00354-23
) describe a new connection linking the carbon storage regulator CsrA to the acid stress response, highlighting new additional layers of complexity.
Publisher
American Society for Microbiology