AUTHOR=Zhou Luoxiong , Wang Lihong , Tian Ping , Bao Tingting , Li Lianbin , Zhao Xin 

TITLE=The LiaFSR and BsrXRS Systems Contribute to Bile Salt Resistance in Enterococcus faecium Isolates

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01048

DOI=10.3389/fmicb.2019.01048

ISSN=1664-302X

ABSTRACT=<p>Two-component systems (TCSs) are dominant regulating components in bacteria for responding to environmental stimuli. However, little information is available on how TCSs in <italic>Enterococcus faecium</italic> respond to bile salts – an important environmental stimulus for intestinal bacteria. In this study, the gene expression of 2 TCSs, BsrXRS and LiaFSR, was positively correlated with survival rates of different <italic>E. faecium</italic> isolates during exposure to ox gall. Moreover, gene disruptions of <italic>bsrR</italic>, <italic>bsrS</italic>, <italic>liaS</italic>, and <italic>liaR</italic> significantly reduced the survival rates of <italic>E. faecium</italic> in the presence of ox gall. Finally, EMSA results indicated that BsrR functioned as a transcription regulator for expression of its own gene as well as lipoate-protein ligase A (<italic>lplA</italic>). Additional 27 potential target genes by BsrR were revealed through <italic>in silico</italic> analyses. These findings suggest that BsrXRS and LiaFSR systems play important roles in bile salt resistance in <italic>E. faecium</italic>.</p>