AUTHOR=Wang Ke-Chuan , Huang Chih-Hung , Ding Shih-Min , Chen Ching-Kuo , Fang Hsu-Wei , Huang Ming-Te , Fang Shiuh-Bin 

TITLE=Role of yqiC in the Pathogenicity of Salmonella and Innate Immune Responses of Human Intestinal Epithelium

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01614

DOI=10.3389/fmicb.2016.01614

ISSN=1664-302X

ABSTRACT=<p>The <italic>yqiC</italic> gene of <italic>Salmonella enterica</italic> serovar Typhimurium (<italic>S</italic>. Typhimurium) regulates bacterial growth at different temperatures and mice survival after infection. However, the role of <italic>yqiC</italic> in bacterial colonization and host immunity remains unknown. We infected human LS174T, Caco-2, HeLa, and THP-1 cells with <italic>S</italic>. Typhimurium wild-type SL1344, its <italic>yqiC</italic> mutant, and its complemented strain. Bacterial colonization and internalization in the four cell lines significantly reduced on <italic>yqiC</italic> depletion. Post-infection production of interleukin-8 and human β-defensin-3 in LS174T cells significantly reduced because of <italic>yqiC</italic> deleted in <italic>S</italic>. Typhimurium. The phenotype of <italic>yqi</italic>C mutant exhibited few and short flagella, fimbriae on the cell surface, enhanced biofilm formation, upregulated type-1 fimbriae expression, and reduced bacterial motility. Type-1 fimbriae, flagella, SPI-1, and SPI-2 gene expression was quantified using real-time PCR. The data show that deletion of <italic>yqiC</italic> upregulated <italic>fimA</italic> and <italic>fimZ</italic> expression and downregulated <italic>flhD, fliZ, invA</italic>, and <italic>sseB</italic> expression. Furthermore, thin-layer chromatography and high-performance liquid chromatography revealed the absence of menaquinone in the <italic>yqiC</italic> mutant, thus validating the importance of <italic>yqiC</italic> in the bacterial electron transport chain. Therefore, YqiC can negatively regulate FimZ for type-1 fimbriae expression and manipulate the functions of its downstream virulence factors including flagella, SPI-1, and SPI-2 effectors.</p>