5 Conclusions
Intracellular accumulation of c-di-GMP in Z. mobilis through biosynthesis and degradation catalyzed by enzymes with DGC and PDE activities activates the biosynthesis of cellulose fibrils for the bacterial cells to self-flocculate with significant advantages in industrial production. Compared to the overexpression of proteins with DGC activity for synthesizing more c-di-GMP from GTP, deactivation of PDE activity to compromise c-di-GMP degradation is preferred for intracellular accumulation of the signal molecule, since this strategy would exert less perturbation on intracellular processes involved with or regulated by GTP. This study provides insights into the regulation of c-di-GMP on the morphological shift in Z. mobilis from unicellular cells to multicellular flocs, as well as guidelines for engineering unicellular strains from this species and other bacteria with the self-flocculating phenotype through rational design. Moreover, this study provides a basis for exploring the mechanism underlying c-di-GMP metabolism in Z. mobilis and its regulation of other intracellular processes.