Tandem GGDEF–EAL Domain Proteins Pleiotropically Modulate c-di-GMP Metabolism Enrolled in Bacterial Cellulose Biosynthesis

Cyclic diguanosine monophosphate (c-di-GMP) is a crucial secondary messenger that regulates bacterial cellulose (BC) synthesis. It is synthesized by diguanylate cyclase (DGC) containing a Gly-Gly-Asp/Glu-Glu-Phe (GGDEF) domain and degraded by phosphodiesterase (PDE) with a Glu-Ala-Leu (EAL) domain. In this work, a systematic analysis of ten GGDEF–EAL tandem domain proteins from Komagataeibacter xylinus CGMCC 2955 assessed their c-di-GMP metabolic functions and effects on BC titer and structure. Of these, five proteins exhibited DGC activity, and five exhibited PDE activity in vitro. GE03 was identified as a bifunctional protein. Most mutant strains deficient in GGDEF-EAL protein showed changes in BC metabolism, motility, and c-di-GMP levels. The combined knockout of identified PDE proteins increased the BC titer by 48.1% compared to the wild type. Overall, our findings advance our understanding of c-di-GMP signaling and its role in BC synthesis, introducing novel concepts and effective strategies for enhancing industrial BC production.