Genetics, Mechanism and Regulation of Cellulose Synthesis inA. Tumefaciens

本文建议继续对产瘤杆菌合成纤维素的机理进行研究。在以前的研究中，纤维素合成所需的两个操作子被鉴定和测序。在同样的研究中，还开发了一种体外纤维素合成系统。利用这种体外纤维素合成系统和细胞（纤维素合成）基因的突变细胞，可以确定每个细胞基因产物在纤维素形成中的作用。通过相同的体外纤维素合成系统和突变体收集，发现了可能的纤维素合成中间体。这些中间体的化学结构将被确定。此外，在植物细胞或植物提取物存在的情况下，A. tummefaciens的纤维素合成增加。将对这一规定的机制进行审查。纤维素是由植物和一些细菌和真菌制造的，是地球上最丰富的生物生产材料之一。它是一种相对简单的分子，由-1,4-葡萄糖分子的线性链组成。然而，纤维素合成的详细机理尚不清楚。现在还不知道是否所有的生物都使用类似的途径来制造纤维素，或者是否不同的生物群体使用不同的途径。对纤维素合成的调控也知之甚少。在本研究项目中，将对农杆菌合成纤维素的机制和调控进行研究。使用细菌研究纤维素合成的优点是细菌相对简单，并且通常可以更容易地确定所需的基因以及在复杂的生物合成途径中相同基因产物的个体作用。在早期的一项研究中，确定了这种细菌形成纤维素的基因。现在，随着突变细胞的收集和无细胞纤维素合成系统的发展，人们希望能够确定纤维素合成的每个基因的功能，纤维素形成途径中的化学步骤将被确定，并且可以进行实验来开始理解微生物途径是如何调节纤维素形成的。＊＊＊

9405844 Matthysse It was propose to continue our investigation of the mechanisms of cellulose synthesis by A. tumefaciens. In previous research, two operons required for cellulose synthesis were identified and sequenced. In the same studies, an in vitro cellulose synthesis system was also developed. With this in vitro cellulose synthesis system together with mutant cells in the cel (cellulose synthesis) genes, the role of each one of the cel gene products in cellulose formation may be determined. By using the same in vitro cellulose synthesis system and mutant collection, putative intermediates in cellulose synthesis were found. The chemical structure of these intermediates will be determined. In addition, cellulose synthesis in A. tumefaciens is increased in the present of plant cells or plant extracts. The mechanism of this regulation will be examined. %%% Cellulose, which is made by plants and by some bacteria and fungi, is one of the most abundant biologically produced materials on earth. It is a relatively simple molecule consisting of a linear chain of beta-1,4-glucose molecules. However, the detailed mechanism of cellulose synthesis is not well understood. It is not now known whether all organisms which make cellulose use similar pathways, or whether there are different pathways used by different groups of organisms. The regulation of cellulose synthesis is also poorly understood. In this research project, the mechanism and regulation of cellulose synthesis by a bacterium called Agrobacterium tumefaciens will be examined. The advantages of using a bacterium to study cellulose synthesis are that the bacteria are relatively simple and often allow more easily for the determination of genes required and the individual role(s) of the same gene products in a complex biosynthetic pathway. In an earlier study, the genes for cellulose formation by this bacterium were determined. Now with a collection of mutant cells and the development of a cell-fre e cellulose synthesis system, it is hoped that the function of each one of the genes of cellulose synthesis can be determined, that the chemical steps in the pathway for cellulose formation will be identified, and that experiments can be undertaken to begin to understand how the microbial pathway is regulated for cellulose formation. ***