Putative functions of EpsK in teichuronic acid synthesis and phosphate starvation in Bacillus licheniformis

Yiyuan Xu; Lijie Yang; Haiyan Wang; Xiaoyu Wei; Yanyan Shi; Dafeng Liang; Mingfeng Cao; Ning He

doi:10.1016/j.synbio.2022.04.001

Putative functions of EpsK in teichuronic acid synthesis and phosphate starvation in Bacillus licheniformis

Synth Syst Biotechnol. 2022 Apr 5;7(2):815-823. doi: 10.1016/j.synbio.2022.04.001. eCollection 2022 Jun.

Authors

Yiyuan Xu^{1

2}, Lijie Yang^{1

2}, Haiyan Wang^{1

2}, Xiaoyu Wei^{1

2}, Yanyan Shi^{1

2}, Dafeng Liang³, Mingfeng Cao^{1

2}, Ning He^{1

2}

Affiliations

¹ Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, PR China.
² The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China.
³ Institute of Bioengineering, Guangdong Academy of Sciences, Guangzhou, 510316, Guangdong, PR China.

Abstract

Extracellular polymeric substances (EPSs) are extracellular macromolecules in bacteria, which function in cell growth and show potential for mechanism study and biosynthesis application. However, the biosynthesis mechanism of EPS is still not clear. We herein chose Bacillus licheniformis CGMCC 2876 as a target strain to investigate the EPS biosynthesis. epsK, a member of eps cluster, the predicted polysaccharide synthesis cluster, was overexpressed and showed that the overexpression of epsK led to a 26.54% decrease in the production of EPS and resulted in slenderer cell shape. Transcriptome analysis combined with protein-protein interactions analysis and protein modeling revealed that epsK was likely responsible for the synthesis of teichuronic acid, a substitute cell wall component of teichoic acid when the strain was suffering phosphate limitation. Further cell cultivation showed that either phosphate limitation or the overexpression of teichuronic acid synthesis genes, tuaB and tuaE could similarly lead to EPS reduction. The enhanced production of teichuronic acid induced by epsK overexpression triggered the endogenous phosphate starvation, resulting in the decreased EPS synthesis and biomass, and the enhanced bacterial chemotaxis. This study presents an insight into the mechanism of EPS synthesis and offers the potential in controllable synthesis of target products.

Keywords: DEGs, Differentially expressed genes; EPS, Extracellular polymeric substance; Extracellular polymeric substance (EPS); PPIs, Protein-protein interactions; Phosphate starvation; Polysaccharides; QS, Quorum sensing; SEM, Scanning electron microscopy; Transcriptome; γ-PGA, γ-polyglutamic acid.