Genomics of Aerobic Cellulose Utilization Systems in Actinobacteria

Cellulose degrading enzymes have important functions in the biotechnology industry, including the production of biofuels from lignocellulosic biomass. Anaerobes including Clostridium species organize cellulases and other glycosyl hydrolases into large complexes known as cellulosomes. In contrast, aerobic actinobacteria utilize systems comprised of independently acting enzymes, often with carbohydrate binding domains. Numerous actinobacterial genomes have become available through the Genomic Encyclopedia of Bacteria and Archaea (GEBA) project. We identified putative cellulose-degrading enzymes belonging to families GH5, GH6, GH8, GH9, GH12, GH48, and GH51 in the genomes of eleven members of the actinobacteria. The eleven organisms were tested in several assays for cellulose degradation, and eight of the organisms showed evidence of cellulase activity. The three with the highest cellulase activity were Actinosynnema mirum, Cellulomonas flavigena, and Xylanimonas cellulosilytica. Cellobiose is known to induce cellulolytic enzymes in the model organism Thermobifida fusca, but only Nocardiopsis dassonvillei showed higher cellulolytic activity in the presence of cellobiose. In T. fusca, cellulases and a putative cellobiose ABC transporter are regulated by the transcriptional regulator CelR. Nine organisms appear to use the CelR site or a closely related binding site to regulate an ABC transporter. In some, CelR also regulates cellulases, while cellulases are controlled by different regulatory sites in three organisms. Mining of genome data for cellulose degradative enzymes followed by experimental verification successfully identified several actinobacteria species which were not previously known to degrade cellulose as cellulolytic organisms

Three-dimensional diffusion weighted imaging of the acute cerebral ischemia rat using 3D MP-RAGE MRI

The purpose of this study was to examine the potential of diffusion-weighted (DW) three-dimensional (3D) MP-RAGE sequence for cerebral ischemia of a rat brain in vivo. The prototype of a DW-3D-MP-RAGE (3D-DWI) sequence was implemented at 2.0T animal experiment MR imager. The advantage of 3D imaging are that you obtain thinner and more slices with better profiles, and better signal-to-noise ratio for an equivalent slice thickness. Since 3D imaging is preferable for obtaining contiguous thin-slice MR images, image data with 3D imaging are expected to volume estimate of imaging area. Three-dimensional calculated absolute apparent diffusion coefficient (ADC) maps were compared with coronal stained (triphenyltetrazolium chloride: TTC) brain sections. From rat experimental results, the region of cerebral ischemia with 3D-DWI and the region of stained brain sections were well in agreement. This technique enables three-dimensional image display of a cerebral ischemia area, and makes it possible to measure the volume of a precise cerebral ischemia area in vivo.Date of Conference: Oct. 30 2010-Nov. 6 201