AUTHOR=Cai Wentong , Cai Xuwang , Yang Yongwu , Yan Shigan , Zhang Haibin 

TITLE=Transcriptional Control of Dual Transporters Involved in α-Ketoglutarate Utilization Reveals Their Distinct Roles in Uropathogenic Escherichia coli

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00275

DOI=10.3389/fmicb.2017.00275

ISSN=1664-302X

ABSTRACT=<p>Uropathogenic <italic>Escherichia coli</italic> (UPEC) are the primary causative agents of urinary tract infections. Some UPEC isolates are able to infect renal proximal tubule cells, and can potentially cause pyelonephritis. We have previously shown that to fulfill their physiological roles renal proximal tubule cells accumulate high concentrations of α-ketoglutarate (KG) and that gene cluster <italic>c5032</italic>–<italic>c5039</italic> contribute to anaerobic utilization of KG by UPEC str. CFT073, thereby promoting its <italic>in vivo</italic> fitness. Given the importance of utilizing KG for UPEC, this study is designed to investigate the roles of two transporters KgtP and C5038 in KG utilization, their transcriptional regulation, and their contributions to UPEC fitness <italic>in vivo</italic>. Our phylogenetic analyses support that <italic>kgtP</italic> is a widely conserved locus in commensal and pathogenic <italic>E. coli</italic>, while UPEC-associated <italic>c5038</italic> was acquired through horizontal gene transfer. Global anaerobic transcriptional regulators Fumarate and nitrate reduction (FNR) and ArcA induced <italic>c5038</italic> expression in anaerobiosis, and C5038 played a major role in anaerobic growth on KG. KgtP was required for aerobic growth on KG, and its expression was repressed by FNR and ArcA under anaerobic conditions. Analyses of FNR and ArcA binding sites and results of EMS assays suggest that FNR and ArcA likely inhibit <italic>kgtP</italic> expression through binding to the –35 region of <italic>kgtP</italic> promoter and occluding the occupancy of RNA polymerases. Gene <italic>c5038</italic> can be specifically induced by KG, whereas the expression of <italic>kgtP</italic> does not respond to KG, yet can be stimulated during growth on glycerol. In addition, <italic>c5038</italic> and <italic>kgtP</italic> expression were further shown to be controlled by different alternative sigma factors RpoN and RpoS, respectively. Furthermore, dual-strain competition assays in a murine model showed that <italic>c5038</italic> mutant but not <italic>kgtP</italic> mutant was outcompeted by the wild-type strain during the colonization of murine bladders and kidneys, highlighting the importance of C5038 under <italic>in vivo</italic> conditions. Therefore, different transcriptional regulation led to distinct roles played by C5038 and KgtP in KG utilization and fitness <italic>in vivo</italic>. This study thus potentially expanded our understanding of UPEC pathobiology.</p>