AUTHOR=Gao Jian-xin , Li Ping , Du Xin-jun , Han Zhong-hui , Xue Rui , Liang Bin , Wang Shuo 

TITLE=A Negative Regulator of Cellulose Biosynthesis, bcsR, Affects Biofilm Formation, and Adhesion/Invasion Ability of Cronobacter sakazakii

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01839

DOI=10.3389/fmicb.2017.01839

ISSN=1664-302X

ABSTRACT=<p><italic>Cronobacter sakazakii</italic> is an important foodborne pathogen that causes neonatal meningitis and sepsis, with high mortality in neonates. However, very little information is available regarding the pathogenesis of <italic>C. sakazakii</italic> at the genetic level. In our previous study, a cellulose biosynthesis-related gene (<italic>bcsR</italic>) was shown to be involved in <italic>C. sakazakii</italic> adhesion/invasion into epithelial cells. In this study, the detailed functions of this gene were investigated using a gene knockout technique. A <italic>bcsR</italic> knockout mutant (Δ<italic>bcsR</italic>) of <italic>C. sakazakii</italic> ATCC BAA-894 showed decreased adhesion/invasion (3.9-fold) in human epithelial cell line HCT-8. Biofilm formation by the mutant was reduced to 50% of that exhibited by the wild-type (WT) strain. Raman spectrometry was used to detect variations in biofilm components caused by <italic>bcsR</italic> knockout, and certain components, including carotenoids, fatty acids, and amides, were significantly reduced. However, another biofilm component, cellulose, was increased in Δ<italic>bcsR</italic>, suggesting that <italic>bcsR</italic> negatively affects cellulose biosynthesis. This result was also verified via RT-PCR, which demonstrated up-regulation of five crucial cellulose synthesis genes (<italic>bcsA, B, C, E, Q</italic>) in Δ<italic>bcsR</italic>. Furthermore, the expression of other virulence or biofilm-related genes, including flagellar assembly genes (<italic>fliA, C, D</italic>) and toxicity-related genes (<italic>ompA, ompX, hfq</italic>), was studied. The expression of <italic>fliC</italic> and <italic>ompA</italic> in the Δ<italic>bcsR</italic> mutant was found to be remarkably reduced compared with that in the wild-type and the others were also affected excepted <italic>ompX</italic>. In summary, <italic>bcsR</italic> is a negative regulator of cellulose biosynthesis but positively regulates biofilm formation and the adhesion/invasion ability of <italic>C. sakazakii</italic>.</p>