AUTHOR=Feng Zheng , El Hag Muhanad , Qin Tao , Du Yinping , Chen Sujuan , Peng Daxin 

TITLE=Residue L193P Mutant of RpoS Affects Its Activity During Biofilm Formation in Salmonella Pullorum

JOURNAL=Frontiers in Veterinary Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.571361

DOI=10.3389/fvets.2020.571361

ISSN=2297-1769

ABSTRACT=<p>The role of alternative sigma factor RpoS in regulating biofilm formation may differ in various <italic>Salmonella</italic> Pullorum strains. In this study, the biofilm-forming ability of two <italic>Salmonella</italic> Pullorum strains S6702 and S11923-3 were compared. The biofilm forming ability of S11923-3 was much stronger than that of S6702. After knocking out the <italic>rpoS</italic> gene, S11923-3Δ<italic>rpoS</italic> had significantly reduced biofilm while S6702Δ<italic>rpoS</italic> demonstrated similar biofilm compared with each parent strain. The analysis of RpoS sequences indicated two amino acid substitutions (L193P and R293C) between S6702 and S11923-3 RpoS. A complementation study confirmed that the expression of S11923-3 RpoS rather than S6702 RpoS could restore the biofilm-forming ability of Δ<italic>rpoS</italic> strains and the L193P mutation contributed to the restoration of the biofilm-forming ability. Further study indicated that RpoS with the L193P mutant had significantly improved expression level and binding activity to RNAP and <italic>csgD</italic> gene promoter, which increased the efficacy of the <italic>csgD</italic> gene promoter and biofilm-forming ability. Therefore, the L193P mutation of RpoS is critical for stronger biofilm formation of <italic>Salmonella</italic> Pullorum.</p>