Discovering the regulatory mechanisms involved in bacterial cellulose biosynthesis

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Extracellular cellulose, an unbranched polymer of --1,4-linked glucopyranose residues, is a crucial component of the biofilm structure of many plant and human pathogens facilitating their attachment to surfaces and providing protection against environmental stressors. Despite the obvious importance of cellulose as a microbial survival strategy, the mechanisms by which environmental signals regulate the synthesis of this important biopolymer are unknown. Acetic acid bacteria (AAB) are ubiquitous in acidic, sugary and alcohol-rich environments. These gram-negative bacteria are important for many biotechnological applications including the synthesis of bacterial cellulose (BC). BC synthesized by AAB consists of an ultrafine network of nanofibres that contribute to its highly crystalline structure and tensile strength making it important for many industrial applications such as paper, pharmaceuticals, wound dressings and tissue scaffolds. AAB can be isolated from fruits and flowers, however, the role cellulose plays in this plant-microbe interaction is not known. The long-range goal of this research program is to elucidate the multiple levels of regulatory control that affect not only the synthesis but also the physicochemical properties of cellulose. This knowledge is key to understanding the role bacterial cellulose plays in microbe-plant interactions and how the cellulose properties affect bacterial survival in the environment. The knowledge gained from this research program will be fundamental in engineering cellulosic materials with unique properties for diverse industrial applications and will be an important step towards finding regulatory targets for the control of cellulosic biofilms. To build on our recent work in this area and to further elucidate the regulatory circuits that control cellulose-mediated plant-microbe interactions, the specific objectives for this granting period will be to 1) characterize the functional role of FixK, a Crp/Fnr transcriptional regulator, in BC biosynthesis; 2) characterize the role phytohomones play in BC regulation; and 3) identify key phytohormone-responsive regulators of BC biosynthesis. This research program will provide interdisciplinary training to highly qualified personnel in the areas of microbiology, molecular biology, genetics, proteomics, transcriptomics, bioinformatics, biochemistry and material science.