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Decoding biomass-sensing regulons of Clostridium thermocellum alternative sigma factors
2017-11-16 | 编辑: | 【 】| | 供稿部门:
    

Lecture: 

Decoding biomass-sensing regulons of Clostridium thermocellum alternative sigma factors 

Lecturer: 

Dr. Iván Muñoz-Gutiérrez, Department of Biomolecular Sciences, The Weizmann Institute of Science, Israel 

Time: 

10:30 am, Nov 22, 2017, Wednesday  

Location: 

214 Meeting Room, Administrative building 

Introduction of Lecturer:  

Iván Muñoz performed his bachelor's degree in biochemical engineering at the Morelia Institute of Technology, Morelia, México. During his bachelor's studies, Ivan was fascinated with the world of enzymes and the use of these biocatalysts in biotechnology. This fascination motivated him to perform his Master's and PhD's studies in the Department of Cellular Bioengineering and Biocatalysis at the Biotechnology Institute of the National Autonomous University of Mexico. During his master's studies, he worked with inulinases (beta-fructosidases). These enzymes have important applications in the food industry; specifically, in Mexico, in the production of tequila and oligosaccharides with prebiotic potential from Agave plants. Subsequently, he decided to move into the biofuels area, and, during his PhD research, Ivan worked with the cell surface display of beta-glucosidases on an ethanologenic Escherichia coli strain. The main objective was to engineer E. coli with the ability to ferment cellobiose into ethanol in one step for the development of the consolidated bioprocessing concept. During the preparation of his PhD thesis, Ivan discovered the cellulosome in the literature and fell in love with it. Hence, he decided to join the lab of Prof. Raphael Lamed as a Postdoctoral Fellow in the Department of Molecular Microbiology and Biotechnology of Tel Aviv University. In Lamed's lab, Ivan started to work on the understanding of the biomass-sensing regulatory systems of cellulosome-producing bacteria – research that he is currently continuing as a Postdoctoral Fellow under the supervision of Prof. Edward A. Bayer in the Department of Biomolecular Sciences at the Weizmann Institute of Science, Rehovot, Israel. 

Major Research Interests:  

General: Enzymology, microbiology, metabolic engineering, fermentation, biomass degradation and biomass-to-biofuels processing, molecular biology, genetic regulation. 

Specific: Genetic regulation of genes encoding saccharolytic enzymes and cellulosomal components; polysaccharide-sensing systems of cellulolytic clostridia; transcriptional regulation by alternative sigma factors in cellulolytic clostridia; production of biocommodities from cellulosic wastes that can replace petroleum-derived products. 

Abstract: 

Clostridium thermocellum is a thermophile capable of converting cellulosic wastes into fermentation products such as ethanol. This bacterium secretes a multi-enzyme system called the cellulosome which consists of a nonhydrolytic scaffoldin subunit that integrates various catalytic subunits, such as cellulases, hemicellulases and pectin-degrading enzymes. The enzymatic composition of the cellulosome is regulated to suit the type of polysaccharide(s) present in the environment. 

During the course of our efforts to gain knowledge about the biomass-sensing mechanisms in C. thermocellum, our research groups discovered a collection of eight alternative s factors that are related to the Bacillus subtilis sI factor. Six of these alternative sI factors have cognate membrane-associated anti-σ factors (RsgI) that contain C-terminal sensory elements localized on the cell surface which comprise carbohydrate-binding modules (RsgI-CBM), glycoside hydrolase modules (RsgI-GH10) or other sugar-binding elements, such as the PA14 motifs. These RsgI-borne sensory elements can bind to different plant-derived polysaccharides, thereby suggesting that this set of σI/RsgIs comprises polysaccharide-sensing systems. 

During the last several years, our research group has focused on demonstrating that individual C. thermocellum sI factors regulate specific cellulosomal genes. We discovered that sI6 and sI3 are implicated in the regulation of genes encoding xylanolytic and pectinolytic enzymes, respectively. Interestingly, both, sI6 and sI3, are able to activate the sI-dependent promoter of the cipA gene, which encodes the major scaffoldin of the cellulosome. Our data support our hypothesis that several crucial cellulosomal genes are regulated by alternative s factors, and their genetic manipulation may have important future biotechnological impact. 

 
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