AUTHOR=Yuan Lingyue , Li Xuan , Du Ling , Su Kewen , Zhang Jiaxue , Liu Pin , He Qiang , Zhang Zhongshuang , Peng Dan , Shen Lifei , Qiu Jingfu , Li Yingli 

TITLE=RcsAB and Fur Coregulate the Iron-Acquisition System via entC in Klebsiella pneumoniae NTUH-K2044 in Response to Iron Availability

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.00282

DOI=10.3389/fcimb.2020.00282

ISSN=2235-2988

ABSTRACT=<p>The iron acquisition system is an essential virulence factor for human infection and is under tight regulatory control in a variety of pathogens. Ferric-uptake regulator (Fur) is one of Fe<sup>2+</sup>-responsive transcription factor that maintains iron homeostasis, and the regulator of capsule synthesis (Rcs) is known to regulate exopolysaccharide biosynthesis. We speculate the Rcs may involve in iron-acquisition given the identified regulator box in the upstream of <italic>entC</italic> that participated in the biosynthesis of enterobactin. To study the coregulation by RcsAB and Fur of <italic>entC</italic>, we measured the β-galactosidase activity and relative mRNA expression of <italic>entC</italic> in WT and mutant strains. The RcsAB- and Fur-protected regions were identified by an electrophoretic mobility shift assay (EMSA) and a DNase I footprinting assay. A regulatory cascade was identified with which Fur repressed <italic>rcsA</italic> expression and reduced RcsAB and <italic>entC</italic> expression. Our study demonstrated that <italic>entC</italic> was coregulated by two different transcriptional regulators, namely, RcsAB and Fur, in response to iron availability in <italic>Klebsiella pneumoniae</italic>.</p>