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Title: Enhanced uptake of potassium or glycine betaine or export of cyclic-di-AMP restores osmoresistance in a high cyclic-di-AMP Lactococcus lactis mutant
Authors: Pham, Huong Thi
Nhiep, Nguyen Thi Hanh
Vu, Thu Ngoc Minh
Huynh, TuAnh Ngoc
Zhu, Yan
Huynh, Anh Le Diep
Chakrabortti, Alolika
Marcellin, Esteban
Lo, Raquel
Howard, Christopher B.
Bansal, Nidhi
Liang, Zhao-Xun
Turner, Mark S.
Woodward, Joshua J.
Keywords: Lactococcus Mutant
DRNTU::Science::Biological sciences
Issue Date: 2018
Source: Pham, H. T., Nhiep, N. T. H., Vu, T. N. M., Huynh, T. N., Zhu, Y., Huynh, A. L. D., . . . Turner, M. S. (2018). Enhanced uptake of potassium or glycine betaine or export of cyclic-di-AMP restores osmoresistance in a high cyclic-di-AMP Lactococcus lactis mutant. PLOS Genetics, 14(8), e1007574-. doi:10.1371/journal.pgen.1007574
Series/Report no.: PLOS Genetics
Abstract: The broadly conserved bacterial signalling molecule cyclic-di-adenosine monophosphate (c-di-AMP) controls osmoresistance via its regulation of potassium (K+) and compatible solute uptake. High levels of c-di-AMP resulting from inactivation of c-di-AMP phosphodiesterase activity leads to poor growth of bacteria under high osmotic conditions. To better understand how bacteria can adjust in response to excessive c-di-AMP levels and to identify signals that feed into the c-di-AMP network, we characterised genes identified in a screen for osmoresistant suppressor mutants of the high c-di-AMP Lactococcus ΔgdpP strain. Mutations were identified which increased the uptake of osmoprotectants, including gain-of-function mutations in a Kup family K+ importer (KupB) and inactivation of the glycine betaine transporter transcriptional repressor BusR. The KupB mutations increased the intracellular K+ level while BusR inactivation increased the glycine betaine level. In addition, BusR was found to directly bind c-di-AMP and repress expression of the glycine betaine transporter in response to elevated c-di-AMP. Interestingly, overactive KupB activity or loss of BusR triggered c-di-AMP accumulation, suggesting turgor pressure changes act as a signal for this second messenger. In another group of suppressors, overexpression of an operon encoding an EmrB family multidrug resistance protein allowed cells to lower their intracellular level of c-di-AMP through active export. Lastly evidence is provided that c-di-AMP levels in several bacteria are rapidly responsive to environmental osmolarity changes. Taken together, this work provides evidence for a model in which high c-di-AMP containing cells are dehydrated due to lower K+ and compatible solute levels and that this osmoregulation system is able to sense and respond to cellular water stress.
ISSN: 1553-7390
DOI: 10.1371/journal.pgen.1007574
Schools: School of Biological Sciences 
Rights: © 2018 Pham et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SBS Journal Articles

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