Investigating the molecular mechanisms of bacterial adaptations to pressure

Abstract

May2025School of ScienceAll organisms must carefully regulate stress response pathways and the rate at which they grow and divide, and hence their size. The vast majority of microbes on Earth live in the deep biosphere, which is comprised of areas with high hydrostatic or lithostatic pressure. The molecular mechanisms underlying the adaptations of these organisms to survive in these extreme environments remain elusive. Despite this, there is great biological significance in understanding how cell growth/division and stress response pathway regulation are altered in these organisms, especially given the role of pressure in food sterilization. In this work, we investigated a pressure-adapted strain of E. coli from the perspective of both stress response and cell size, two essential properties of life. First, we determined that even pressure-adapted organisms are stressed by pressure but distinctly compared to non-adapted organisms. In particular, we demonstrated that the upregulation of the molecular chaperone, GroEL, was favored over that of the DnaK chaperone in response to pressure shock in the pressure-adapted strain, whereas the opposite was true for the non-adapted strain. We interpret this differential regulation as a consequence of the distinct functions of these two proteins. Our results also suggest that the alternative sigma factor RpoE and its anti-sigma factors may work in concert as pressure sensors. Second, we showed that the small cell size phenotype of the pressure-adapted strain is the result of the slow growth of the strain rather than an increase in the accumulation of cell division machinery. Slow growth may result from mutations in GlnA, which is implicated in the activation of the nitrogen starvation response, as well as in the RpoB subunit of RNA Polymerase. We also performed the first ever live cell imaging of FtsZ under pressure, demonstrating that the division ring formed by FtsZ is disrupted under pressure in vivo. Taken together, our results expand upon our understanding of how microbes can adapt to live in high pressure environments and survive pressure shocks.Ph