How enterobacteria perceive host environment: sensing osmotic upshift by the PhoQ/PhoP two-component system
Whether residing in or invading the host, enterobacteria have to deal with host-related stress conditions. These stress factors also serve as sensory cues, informing bacteria that they are present inside the host. Scientists at the Max Planck Institute for Terrestrial Microbiology in Marburg have found that the PhoQ/PhoP two-component system can sense osmotic upshift, a key stimulus associated with the host. Their work was published this week in the journal PNAS.
The PhoQ/PhoP two-component system plays an essential role in the response of enterobacteria to the environment of their mammalian hosts. Jing Yuan and colleagues could now show that PhoQ senses osmotic upshift, in addition to other host-associate stimuli such as low pH, magnesium limitation and antimicrobial peptides. Interestingly, the detection of osmotic upshift does not require the presence of the PhoQ periplasmic sensor domain, which is necessary for detection of most other previously established stimuli. Instead, the detection mechanism seems to rely on a conformational change within the transmembrane domain of PhoQ, induced by perturbation of physical properties of the cell membrane under hyperosmotic conditions. This proposed mechanism was further supported by molecular dynamics simulations.
The PhoQ-mediated osmosensing increases bacterial fitness under hyperosmotic conditions found inside the host, and it is likely to play an important role in the regulation of virulence.
Jing Yuan, Fan Jin, Timo Glatter and Victor Sourjik (2017) Osmosensing by the bacterial PhoQ/PhoP two-component system. Proc Natl Acad Sci USA. doi:10.1073/pnas.1717272114.