Multimethod approach to understand the assembly of cellulose fibrils in the biosynthesis of bacterial cellulose
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The production of controlled bacterial cellulose structures for various applications requires a better understanding on the mechanism of cellulose biosynthesis as well as proper tools for structural characterization of the materials. In this work, bacterial celluloses synthesized by an Asaia bogorensis strain known to produce fine cellulose fibrils and a commonly used Komagataeibacter xylinus strain were characterized using a comprehensive set of methods covering multiple levels of the hierarchical structure. FT-IR spectroscopy and x-ray diffraction were used to analyse the crystal structure and crystallite dimensions, whereas scanning and transmission electron microscopy, atomic force microscopy, and small-angle x-ray and neutron scattering were employed to obtain information on the higher-level fibrillar structures. All methods yielded results consistent with the A. bogorensis cellulose fibrils being thinner than the K. xylinus fibrils on both the level of individual cellulose microfibrils and bundles or ribbons thereof, even though the exact values determined for the lateral fibril dimensions depended slightly on the method and sample preparation. Particularly, the width of microfibril bundles determined by the microscopy methods differed due to shrinkage and preferred orientation caused by drying, whereas the microfibril diameter remained unaffected. The results were used to understand the biological origin of the differences between the two bacterial celluloses.
KeywordsBacterial cellulose Structural characterization Cellulose biosynthesis Small-angle scattering
This study was funded by the Japan Society for the Promotion of Science (ID no. P15092), Emil Aaltonen Foundation, and the Core Research for Evolutional Science and Technology (CREST) – Japan Science and Technology Agency (JST) (grant no. JPMJCR13B2). The ILL (proposal no. TEST-2747) and ESRF (final numbers 02-01-882 and 02-01-883) are thanked for providing beamtime. The SEM observations and XRD measurements were done with the courtesy of Prof. Hiroyuki Yano at the Research Institute for Sustainable Humanosphere (RISH), Kyoto University. The TEM observations were carried out with the Analysis and Development system for Advanced Materials (ADAM) of RISH, Kyoto University. The AFM imaging was done at the AFM platform of the PSCM and Alain Panzarella from the ESRF/PSCM is thanked for experimental support. The SAXS experiments were performed on the French CRG beamline D2am at the ESRF and Dr. Isabelle Morfin from CNRS/University of Grenoble Alpes, LIPhy is thanked for providing assistance in using the beamline. This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 research and innovation programme under the SINE2020 project, grant agreement no. 654000.
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