AUTHOR=Ling Jun , Zhu Runjie , Laborda Pedro , Jiang Tianping , Jia Yifan , Zhao Yangyang , Liu Fengquan 

TITLE=LbDSF, the Lysobacter brunescens Quorum-Sensing System Diffusible Signaling Factor, Regulates Anti- Xanthomonas XSAC Biosynthesis, Colony Morphology, and Surface Motility

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01230

DOI=10.3389/fmicb.2019.01230

ISSN=1664-302X

ABSTRACT=<p><italic>Lysobacter</italic> species are emerging as novel sources of antibiotics, but the regulation of these antibiotics has not been thoroughly elucidated to date. In this work, we identified a small diffusible signaling factor (DSF) molecule (<italic>Lb</italic>DSF) that regulates the biosynthesis of a novel <italic>Xanthomonas</italic>-specific antibiotic compound (XSAC) in <italic>Lysobacter brunescens</italic> OH23. <italic>Lb</italic>DSF was isolated from the culture broth of <italic>L. brunescens</italic> OH23, and the chemical structure of the molecule was determined by NMR and MS. The <italic>Lb</italic>DSF compound induced GUS expression in a reporter strain of <italic>Xanthomonas campestris</italic> pv. <italic>campestris</italic> FE58, which contained the <italic>gus</italic> gene under the control of a DSF-inducible <italic>engXCA</italic> promoter. <italic>Lb</italic>DSF production was found to be linked to the enoyl-CoA hydratase RpfF and dependent on the two-component regulatory system RpfC (hybrid sensor histidine kinase)/RpfG (response regulator), and <italic>Lb</italic>DSF production was increased 6.72 times in the Δ<italic>rpfC</italic> compared to wild-type OH23. <italic>Lb</italic>DSF-regulated XSAC production was dramatically decreased in Δ<italic>rpfF</italic>, Δ<italic>rpfC</italic>, and Δ<italic>rpfG</italic>. Additionally, a significant reduction in surface motility and a number of changes in colony morphology was observed in the Δ<italic>rpfF</italic>, Δ<italic>rpfC</italic>, and Δ<italic>rpfG</italic> compared to the wild-type OH23. The exogenous <italic>Lb</italic>DSF significantly increased XSAC production in wild-type OH23 and recovered the XSAC biosynthetic ability in Δ<italic>rpfF</italic>. Taken together, these results showed that <italic>Lb</italic>DSF is a fatty-acid-derived DSF that positively regulates XSAC biosynthesis, cell morphology, and surface motility. Moreover, the RpfC/RpfG quorum-sensing signal transduction pathway mediates XSAC biosynthesis. These findings may facilitate antibiotic production through genetic engineering in <italic>Lysobacter</italic> spp.</p>