AUTHOR=Sun Hao , Song Yajun , Chen Fang , Zhou Changhong , Liu Peng , Fan Yu , Zheng Yangyang , Wan Xuehua , Feng Lu 

TITLE=An ArcA-Modulated Small RNA in Pathogenic Escherichia coli K1

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.574833

DOI=10.3389/fmicb.2020.574833

ISSN=1664-302X

ABSTRACT=<p><italic>Escherichia coli</italic> K1 is the leading cause of meningitis in newborns. Understanding the molecular basis of <italic>E. coli</italic> K1 pathogenicity will help develop treatment of meningitis and prevent neurological sequelae. <italic>E. coli</italic> K1 replicates in host blood and forms a high level of bacteremia to cause meningitis in human. However, the mechanisms that <italic>E. coli</italic> K1 employs to sense niche signals for survival in host blood are poorly understood. We identified one intergenic region in <italic>E. coli</italic> K1 genome that encodes a novel small RNA, sRNA-17. The expression of sRNA-17 was downregulated by ArcA in microaerophilic blood. The Δ<italic>sRNA-17</italic> strain grew better in blood than did the wild-type strain and enhanced invasion frequency in human brain microvascular endothelial cells. Transcriptome analyses revealed that sRNA-17 regulates tens of differentially expressed genes. These data indicate that ArcA downregulates the <italic>sRNA-17</italic> expression to benefit bacterial survival in blood and penetration of the blood–brain barrier. Our findings reveal a signaling mechanism in <italic>E. coli</italic> K1 for host adaptation.</p>