Regulated patterns of bacterial movements based on their secreted cellulose nanofibers interacting interfacially with ordered chitin templates.

Gluconacetobacter xylinus, a gram-negative bacterium that synthesizes and extrudes a cellulose nanofiber in SH media moves in random manners, resulting in 3D-network structure of the secreted nanofibers termed a pellicle. In this study, the bacterial movement was successfully regulated to be in a waving manner when cultured on ordered templates made of chitin. Interestingly, by addition of more cellulose into the chitin ordered templates, the waving pattern was getting close to a linear or straight manner. Real time video analysis and other visualization techniques clarified that the regulation of the moving manners was due to the interfacial interaction between the secreted nanofibers and the template surfaces. Furthermore, the changing of the pattern due to the cellulose content in the ordered templates appeared to depend on the magnitude of the interaction between the template and nanofibers. This regulated autonomous deposition of the fibers will build patterned 3D-structure with unique properties on the surface of the templates, leading to a novel type of nanotechnology using biological systems with biomolecular nano-templates to design 3D-structures.

Novel tool for characterization of noncrystalline regions in cellulose: a FTIR deuteration monitoring and generalized two-dimensional correlation spectroscopy.

Our previous results indicated that noncrystalline regions in a regenerated cellulose film comprised at least three domains engaged in different manners of molecular assembly [Kondo et al. In Cellulose Derivatives; Heinze, T. J., Glasser, W. G., Eds.; ACS Symposium Series 688; American Chemical Society: Washington, DC, 1998; Chapter 12]. In this article, we attempt to characterize each of the three noncrystalline domains in the film. The method used was a FTIR monitoring of deuteration from hydroxyl (OH) groups to OD, leading to the two-dimensional (2D) correlation analysis. The time-scan spectra in the OH-OD exchanging reaction were transformed into two kinds of 2D correlation spectra, the synchronous and the asynchronous spectra. Of the two, some cross-peaks were found in the latter spectrum. This suggests that the asynchronous 2D correlation spectrum could differentiate the contribution of OH groups due to different frequencies of hydrogen bonds in each domain. Here we will show the validity of this 2D correlation method as a powerful tool to predict hydrogen-bonding networks of the noncrystalline domains in cellulose.

Biodirected epitaxial nanodeposition of polymers on oriented macromolecular templates.

Biodirected epitaxial nanodeposition of polymers was achieved on a template with an oriented molecular surface. Acetobacter xylinum synthesized a ribbon of cellulose I microfibrils onto a fixed, nematic ordered substrate of glucan chains with unique surface characteristics. The substrate directed the orientation of the motion due to the inverse force of the secretion during biosynthesis, and the microfibrils were aligned along the orientation of the molecular template. Using real-time video analysis, the patterns and rates of deposition were elucidated. Field emission scanning electron microscopy revealed that a strong molecular interaction allowed for the deposition of nascent biosynthesized 3.5-nm cellulose microfibrils with inter-microfibrillar spacings of 7-8 nm on the surface of the template. The cellulose was deposited parallel to the molecular orientation of the template. Directed cellulose synthesis and ordered movement of cells were observed only by using a nematic ordered substrate made from cellulose, and not from ordered crystalline cellulose substrates or ordered cellulose-related synthetic polymers such as polyvinyl alcohol. This unique relationship between directed biosynthesis and the ordered fabrication from the nano to the micro scales could lead to new methodologies for the design of functional materials with desired nanostructures.