The IS6770 Insertion Sequence Modifies the Transcription Pattern of the kup gene, Encoding the Potassium Symporter, in Enterococcus faecalis JH2-2 under Low pH Conditions

TABORRA, ME; ACCIARRI, G; BLANCATO, VS; MAGNI, C

Rosario

Congreso; LIX Reunión Anual de SAIB; 2023

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Enterococcus faecalis is a phylogenetically and industrially relevant microorganism associated withLactic Acid Bacteria. Some strains of this bacterium are employed as probiotics in commercialapplications, while others serve as the principal component in starter cultures for regional cheeseproduction. However, over the last decade, this species has emerged as an opportunistic multiresistantpathogen, raising concerns about its impact on human health. E. faecalis is adapted to tolerate multipleand different environmental stress conditions. The coordination protons, sodium and potassium of thehomeostasis not only allows the generation of metabolic energy that guarantees the transport ofnutrients but also is essential for the response to stress. Recently, we identified multiple potassiumtransporter systems in E. faecalis, including the Ktr systems (KtrAB and KtrAD), Kup, KimA and Kdpcomplex (KdpFABC). In this study, we observed a modification in the promoter region of the kup gene,which code for the Kup protein in the JH2-2 strain. This chance occurred because of a complete copy ofan IS30 family insertion sequence, specifically IS6770, was inserted. To analyze the influence of IS6770 onthe expression of the kup gene, we conducted a mapping of the promoter region of this gene in the E.faecalis JH2-2 and a V19 strain (V583-derived clinical strain), employing fluorescence gene reporters. Inaddition, a transcriptional analysis of the kup gene was executed in the E. faecalis V583-derived strain(a strain free of IS30-related insertion element), to determine the transcriptional start site of this gene.Finally, the expression of the kup gene was assessed through RT-qPCR under different pH-stressconditions. A strong induction of the kup gene was observed at initial pH 5.0 in the E. faecalisV583-derived strain. Nonetheless, in the E. faecalis JH2-2 strain, this activation was not observed, as thepresence of IS6770 impeded the transcription process. In conclusion, the identification of alterations inthe kup gene promoter region in E. faecalis JH2-2 due to the presence of IS6770 highlights the potentialimplications for gene expression regulation, which may be linked to the observed differences inbehavior between strains.