Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Regulation of c-di-AMP levels during osmotic stress in bacteria. (#346)

Huong Pham 1 , Nguyen Nhiep 1 , Thu Vu 1 , Esteban Marcellin 1 , Raquel Lo 1 , Nidhi Bansal 1 , Liang Zhao-Xun 2 , Mark Turner 1
  1. The University of Queensland, ST LUCIA, QLD, Australia
  2. School of Biological Sciences, Nanyang Technological University, Singapore

Nucleotide signalling pathways in bacteria are key regulators of cellular responses under external stimuli. Cyclic di-adenosine monophosphate (c-di-AMP) is one of recently discovered messengers in a broad range of bacteria that regulates numerous important cellular processes, however, signals that trigger its accumulation or depletion are poorly understood.  Levels of c-di-AMP have been found to inversely correlate with bacterial osmoresistance due to inhibition of potassium and compatible solute uptake systems. In this study, a genetic screen revealed several gain-of-function suppressor mutations in a Kup family potassium transporter that restored osmoresistance in a high c-di-AMP phosphodiesterase Lactococcus lactis mutant. Surprisingly these mutations led to significantly elevated c-di-AMP levels. Constitutive potassium uptake was found to trigger c-di-AMP accumulation, possibly in response to increased turgor pressure. In agreement with this, c-di-AMP levels in resting and energised Lactococcus, Lactobacillus, Staphylococcus and Listeria were found to be rapidly responsive to external osmolarity changes. These results demonstrate a feedback loop exists whereby c-di-AMP regulates osmoresistance and is in turn modulated by cellular osmotic perturbations in bacteria.