AUTHOR=Zhou Shuqin , Zhuang Yijing , Zhu Xiaojuan , Yao Fen , Li Haiyan , Li Huifang , Zou Xiaoguang , Wu Jianhua , Zhou Huifang , Nuer Gulibaier , Huang Yuanchun , Li Shao , Peng Qing 

TITLE=YhjX Regulates the Growth of Escherichia coli in the Presence of a Subinhibitory Concentration of Gentamicin and Mediates the Adaptive Resistance to Gentamicin

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01180

DOI=10.3389/fmicb.2019.01180

ISSN=1664-302X

ABSTRACT=<p>The mechanisms of adaptive resistance of <italic>Escherichia coli</italic> to aminoglycosides remain unclear. Our RNA-Seq study found that expression of <italic>yhjX</italic> was markedly upregulated during initial exposure to subinhibitory concentrations of gentamicin. The expression of <italic>yhjX</italic> was then downregulated dramatically during a second exposure to gentamicin compared to the first exposure. <italic>YhjX</italic> encodes a putative transporter of the major facilitator superfamily, which is known to be the sole target of the YpdA/YpdB two-component system, the expression of which is highly and specifically induced by pyruvate. To investigate the effect of <italic>yhjX</italic> on the adaptive resistance of <italic>E. coli</italic>, in the present study, we constructed <italic>yhjX</italic> deletion and complemented strains of <italic>E. coli</italic> ATCC25922. Changes in extracellular pyruvate levels of wide-type and <italic>yhjX</italic> mutant were measured to determine whether YhjX functions as a pyruvate transporter. The results showed that <italic>yhjX</italic> deletion improved the growth of <italic>E. coli</italic> in medium containing subinhibitory concentrations of gentamicin. The <italic>yhjX</italic> deletion mutant did not exhibit adaptive resistance to subinhibitory concentrations of gentamicin. YhjX might not function as a pyruvate efflux pump in <italic>E. coli</italic> but was associated with the decrease following a sharp increase in the extracellular pyruvate level. Our findings indicate that <italic>yhjX</italic> regulates the growth of <italic>E. coli</italic> in the presence of a subinhibitory concentration of gentamicin and mediates the adaptive resistance to gentamicin.</p>