AUTHOR=Zhu Yao lei , Hou Hong man , Zhang Gong liang , Wang Yi fang , Hao Hong shun 

TITLE=AHLs Regulate Biofilm Formation and Swimming Motility of Hafnia alvei H4

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01330

DOI=10.3389/fmicb.2019.01330

ISSN=1664-302X

ABSTRACT=<p>The aim of this study was to evaluate the role of <italic>N</italic>-acyl homoserine lactones (AHLs) in the regulation of swimming motility of <italic>Hafnia alvei</italic> H4 and its biofilm formation on 96-well plate, glass and stainless-steel surfaces. The <italic>luxI</italic> gene, which codes for an enzyme involved in AHL synthesis, was deleted to generate a <italic>luxI</italic> mutant (Δ<italic>luxI</italic>). The mutant produced no AHL, and the relative expression of the <italic>luxR</italic> gene was significantly (<italic>P</italic> &lt; 0.05) decreased. In addition, <italic>q</italic>RT-PCR analysis showed that the relative expression of the <italic>luxR</italic> gene in Δ<italic>luxI</italic> was stimulated by the presence of exogenous AHLs (C4-HSL, C6-HSL, and 3-o-C8-HSL) added at concentrations ranging from of 50–250 μg/ml. Among the three AHLs, C6-HSL had the strongest effect. The ability of Δ<italic>luxI</italic> to form biofilm on 96-well plate, glass and stainless-steel surfaces was significantly reduced (<italic>P</italic> &lt; 0.05) compared with the wild type (WT), but was increased when provided with 150 μg/ml C4-HSL, whereas C6-HSL and 3-o-C8-HSL had no effect. Scanning electron microscopy analysis of the biofilm revealed less bacteria adhering to the surface of stainless-steel and fewer filaments were found binding to the cells compared with the WT. Furthermore, Δ<italic>luxI</italic> also exhibited significant (<italic>P</italic> &lt; 0.05) decrease in the expression of biofilm- and swimming motility-related genes, <italic>flgA</italic>, <italic>motA</italic> and <italic>cheA</italic>, consistent with the results observed for biofilm formation and swimming motility. Taken together, the results suggested that in <italic>H. alvei</italic> H4, C4-HSL may act as an important molecular signal through regulating the ability of the cells to form biofilm, as well as through regulating the swimming motility of the cell, and this could provide a new way to control these phenotypes of <italic>H. alvei</italic> in food processing.</p>