Authors
Cote, J., Chatterjee, P., Garcia, M., Tao, R., Mathijssen, A. J., Pohlschroder, M.
Abstract
Quorum sensing (QS) enables microorganisms--including bacteria, eukaryotes, and viruses--to coordinate collective behaviors in response to population density. Despite their ecological and evolutionary significance, QS mechanisms in Archaea remain poorly characterized. The halophilic archaeon Haloferax volcanii provides a model for archaeal QS, transitioning from motile rods to non-motile disks in a density-dependent response to a secreted disk-forming signal (DFS). To identify components of the DFS regulatory network, we screened for spontaneous mutants that retained motility in DFS-containing soft-agar medium. One candidate, HVO_1357, encodes a predicted response regulator located adjacent to a histidine kinase (HVO_1356) and a second response regulator (HVO_1358), consistent with an extended two-component regulatory system (TCS). Based on our results, these genes encode quorum-sensing associated regulators (Qar), therefore, we propose rename them qarA (HVO_1357), qarB (HVO_1356), and qarC(HVO_1358). Deletion of qarA enabled cells to swim on DFS-containing soft-agar plates and conferred hypermotility on standard soft-agar media; however, these phenotypes were not due to changes in motility-related parameters, but a reduced sensitivity to DFS for induction of the non-motile, disk-shaped state. In contrast, {Delta}qarB and {Delta}qarC strains were non-motile and exhibited premature disk formation during normal growth. Suppressor mutations that restored motility to {Delta}qarB and {Delta}qarC mapped exclusively to qarA, suggesting QarA is the central regulator of this system. Transcriptomic analyses revealed that qarA deletion leads to upregulation of genes involved in motility and rod-shape formation. Together, these findings reveal qarABC as a DFS-responsive regulatory module and represent the first TCS in archaea shown to control QS-dependent behavior.
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bioRxiv
The authors list and abstract were imported from bioRxiv on 12 Nov 2025.
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