AUTHOR=Liu Xiaolin , Zhang Kaiye , Liu Yanan , Zou Desheng , Wang Dandan , Xie Zhihong 

TITLE=Effects of Calcium and Signal Sensing Systems on Azorhizobium caulinodans Biofilm Formation and Host Colonization

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.563367

DOI=10.3389/fmicb.2020.563367

ISSN=1664-302X

ABSTRACT=<p>Biofilm formation is important for establishing plants-microbe associations. The role of calcium on biofilm formation has been studied in many bacteria except rhizobia. In this study, we investigated the role of calcium for biofilm formation in <italic>Azorhizobium caulindans</italic>, which forms nodules in the stem and root of its host plant <italic>Sesbania rostrata</italic>. We found that calcium is essential for <italic>A. caulindans</italic> biofilm formation, in addition to the presence of extracellular matrix components, eDNA and proteins. Also, calcium-mediated biofilm formation was tested with chemotaxis, motility, cyclic di-GMP synthesis, and quorum sensing mutants. Finally, calcium was found to promote <italic>S. rostrata</italic> root colonization of <italic>A. caulinodans</italic>. In total, these results show that calcium is essential for <italic>A. caulindans</italic> biofilm formation, and it affects the interaction between <italic>A. caulinodans</italic> and host plant.</p>