Single-molecule investigations of single-chain cellulose biosynthesis

Cellulose biosynthesis in sessile bacterial colonies originates in the membrane -integrated bacterial cellulose synthase (Bcs) AB complex. We utilize optical tweezers to measure single-strand cellulose biosynthesis by BcsAB from Rhodobacter sphaeroides. Synthesis depends on uridine diphosphate glucose, Mg2+, and cyclic diguanosine monophosphate, with the last displaying a retention time of similar to 80 min. Below a stall force of 12.7 pN, biosynthesis is relatively insensitive to force and proceeds at a rate of one glucose addition every 2.5 s at room temperature, increasing to two additions per second at 37 degrees. At low forces, conformational hopping is observed. Single-strand cellu-lose stretching unveiled a persistence length of 6.2 nm, an axial stiffness of 40.7 pN, and an ability for complexes to maintain a tight grip, with forces nearing 100 pN. Stretching experiments exhibited hysteresis, suggesting that cellulose microstructure underpinning robust biofilms begins to form during synthesis. Cellohexaose spontane-ously binds to nascent single cellulose strands, impacting polymer mechanical proper-ties and increasing BcsAB activity.

Automated summary

Cellulose biosynthesis in bacterial colonies depends on the membrane-integrated bacterial cellulose synthase AB complex. The synthesis process is influenced by various substances and the complex has a strong gripping ability. Stretching experiments revealed the formation of cellulose microstructure during synthesis and the impact of cellohexaose on enzyme activity and polymer mechanical properties.