cells Article Interplay between Sublethal Aminoglycosides and Quorum Sensing: Consequences on Survival in V. cholerae André Carvalho 1,2,† , Evelyne Krin 1,† , Chloé Korlowski 1 , Didier Mazel 1, * and Zeynep Baharoglu 1, *   Citation: Carvalho, A.; Krin, E.; Korlowski, C.; Mazel, D.; Baharoglu, Z. Interplay between Sublethal Aminoglycosides and Quorum Sensing: Consequences on Survival in V. cholerae. Cells 2021, 10, 3227. https://doi.org/10.3390/cells10113227 Academic Editor: Mahmoud Huleihel Received: 1 October 2021 Accepted: 16 November 2021 Published: 18 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Unité Plasticité du Génome Bactérien, Institut Pasteur, UMR3525 CNRS, 75015 Paris, France; andre-filipe.paulino-carvalho@pasteur.fr (A.C.); evelyne.krin@pasteur.fr (E.K.); chloe.korlowski@gmail.com (C.K.) 2 Collège Doctoral, Sorbonne Université, 75005 Paris, France * Correspondence: didier.mazel@pasteur.fr (D.M.); zeynep.baharoglu@pasteur.fr (Z.B.) † Authors contributed equally. Abstract: Antibiotics are well known drugs which, when present above certain concentrations, are able to inhibit the growth of certain bacteria. However, a growing body of evidence shows that even when present at lower doses (subMIC, for sub-minimal inhibitory concentration), unable to inhibit or affect microbial growth, antibiotics work as signaling molecules, affect gene expression and trigger important bacterial stress responses. However, how subMIC antibiotic signaling interplays with other well-known signaling networks in bacteria (and the consequences of such interplay) is not well understood. In this work, through transcriptomic and genetic approaches, we have explored how quorum-sensing (QS) proficiency of V. cholerae affects this pathogen’s response to subMIC doses of the aminoglycoside tobramycin (TOB). We show that the transcriptomic signature of V. cholerae in response to subMIC TOB depends highly on the presence of QS master regulator HapR. In parallel, we show that subMIC doses of TOB are able to negatively interfere with the AI-2/LuxS QS network of V. cholerae, which seems critical for survival to aminoglycoside treatment and TOB-mediated induction of SOS response in this species. This interplay between QS and aminoglycosides suggests that targeting QS signaling may be a strategy to enhance aminoglycoside efficacy in V. cholerae. Keywords: quorum sensing; aminoglycosides; SOS response; Vibrio cholerae; bacterial signaling; antibiotic tolerance 1. Introduction Many bacterial species secrete small diffusible signaling molecules to synchronize mul- ticellular behaviors which allow them to adapt and survive in natural environments [1,2]. The most studied intercellular communication mechanism is quorum-sensing (QS), which monitors local population density [3,4]. QS is achieved via the production and detection of extracellular small molecules called autoinducers. At low cell density, autoinducers diffuse away, but at high cell density their concentration increases and triggers synchronization of gene expression in bacterial populations. Gram-negative bacteria are able to produce and detect several classes of autoinducers. Autoinducer 1 (AI-1) is a species-specific signaling molecule, while autoinducer 2 (AI-2), which is produced by Gram-negative and Gram- positive bacteria, is able to mediate both intra and interspecies QS communication [5,6]. Vibrio cholerae, the causative agent of cholera disease, produces both autoinducers. AI-1, called cholera AI-1 (CAI-1), is produced by the CqsA protein and sensed by CqsS, while AI-2 is produced by LuxS and sensed by LuxQ, via LuxP periplasmic protein. The QS regulatory network of V. cholerae relies on a well described phosphorylation cascade (Figure 1). At low cell density, CqsS and LuxPQ work as kinases and phosphorylate LuxU which will then transfer the phosphate to the regulator LuxO. Phosphorylated LuxO will then trigger the expression of four small RNAs (qrr1–4) which in turn allow for translation of AphA (master regulator of low cell density), while inhibiting that of Cells 2021, 10, 3227. https://doi.org/10.3390/cells10113227 https://www.mdpi.com/journal/cells