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BISCEm (https://www.unilim.fr/biscem/), acronyme de Biologie Intégrative Santé Chimie Environnement, est une plateforme technologique créée par l’Institut de recherche GEIST en 2017. La plateforme regroupe des équipements de pointe permettant la réalisation d’analyses moléculaires, cellulaires et tissulaires et d’expériences sur des animaux, dans le strict respect de la règlementation en vigueur et du bien-être animal. La réalisation des prestations, la formation à l’utilisation des équipements, les conseils dans la conception des expériences et dans l’interprétation des résutats, la veille technologique et la gestion de la plateforme sont assurés par une équipe d’une vingtaine d’agents hautement qualifiés. La plateforme est ouverte à toutes les structures de recherche, publiques ou privées.

The viral load of the ubiquitous and nonpathogenic torque teno virus (TTV) is associated with the grade of immunosuppression of its host. The development of next-generation sequencing (NGS) allowed to describe the human virome of the blood compartment in transplanted patients, and showed that TTV is the most important part of the virome. This study is a descriptive retrospective pilot study of sequencing plasma samples from 15 matched donors and recipients. After sample processing, nucleic acids were amplified by rolling circle amplification and submitted to NGS by ion proton sequencing technology. Results were analyzed after mapping of reads on the 29 TTV reference genomes and de novo assembling of the reads with MIRA software. The number of TTV species present in donors and recipients was, on average, 12 in donors and 33 in recipients. TTV species predominantly present in donors were TTV-13 and TTV-18; and in recipients were TTV-P15-2, TTV-27, TTV-HD14a, and TTV-22. We highlighted a significant variability in abundance and composition in sequential samples from recipients. Temporal evolution of TTV populations was clearly observed in recipients, but no preferential transmission of a species from donor to recipient was evidenced. Diversity and population expansion were observed in kidney recipients. Further study of TTV species could help assess the potential impact of each species of this virus.

International audience; Class 1 integrons are widespread genetic elements responsible for dissemination of antibiotic resistance among Gram-negative bacteria. Integrons allow bacteria to capture and express gene cassettes (GCs) via an integrase (IntI1) and a promoter (Pc) contained in the integron functional platform. GCs are transcribed from Pc, of which 13 variants of different strengths have been described, or, occasionally, from both Pc and a second promoter (P2). The intI1 promoter (PintI1) is repressed by LexA, which is the transcriptional repressor of the global regulatory SOS response network. Moreover, PintI1 lies face to face with Pc and overlaps P2, both configurations being propitious to transcriptional interference (TI). In this study, we analyzed possible transcriptional interference by quantifying transcripts produced from Pc, P2, and PintI1. We found that the Pc promoter interferes with the level of intI1 transcription but that this effect depends on the Pc variant: the strong Pc variant prevents intI1 expression, in contrast to the other variants. Although P2 formation results in LexA binding site disruption and thus prevents SOS regulation of intI1 expression, P2 does not interfere with PintI1. These findings reveal a tight relationship between GC and integrase expression.

Emilie Guerin, Guillaume Cambray, Sandra Da Re, Didier Mazel, Marie-Cecile Ploy E. Guerin, S. Da Re : Universite de Limoges, EA3175 ; Inserm, equipe Avenir Inserm, faculte de medecine, Limoges, France. G. Cambray, D. Mazel : Institut Pasteur, unite Plasticite du genome bacterien, Paris, 28, rue du Docteur Roux, 75015 Paris, France. M.C. Ploy : Universite de Limoges, EA3175, Equipe Avenir Inserm, Limoges, France. marie-cecile.ploy@unilim.fr NOUVELLE

International audience; The qnr genes are plasmid-borne fluoroquinolone-resistance determinants widespread in Enterobacteriaceae. Three families of qnr determinants (qnrA, B and S) have been described, but little is known about their expression and regulation. Two new determinants, qnrC and qnrD, have been found recently. Here, we describe the characterization of the qnrB2 promoter and the identification of a LexA-binding site in the promoter region of all qnrB alleles. LexA is the central regulator of the SOS response to DNA damage. We show that qnrB2 expression is regulated through the SOS response in a LexA/RecA-dependent manner, and that it can be induced by the quinolone ciprofloxacin, a known inducer of the SOS system. This is the first description of direct SOS-dependent regulation of an antibiotic-resistance mechanism in response to the antibiotic itself.

International audience; Integrons are found in the genome of hundreds of environmental bacteria but are mainly known for their role in the capture and spread of antibiotic resistance determinants among Gram-negative pathogens. We report a direct link between this system and the ubiquitous SOS response. We found that LexA controlled expression of most integron integrases and consequently regulated cassette recombination. This regulatory coupling enhanced the potential for cassette swapping and capture in cells under stress, while minimizing cassette rearrangements or loss in constant environments. This finding exposes integrons as integrated adaptive systems and has implications for antibiotic treatment policies.