Transcriptomic analysis of Clostridium thermocellumATCC 27405 cellulose fermentation

BMC Microbiology

Research Article

Catherine K McKeown¹  Miguel Rodriguez²  Jonathan R Mielenz²  Steven D Brown²  Babu Raman³ 

[1] Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, 37831, Oak Ridge, TN, USA;Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, 37831, Oak Ridge, TN, USA;BioEnergy Science Center (BESC), Oak Ridge National Laboratory, One Bethel Valley Road, 37831, Oak Ridge, TN, USA;Biosciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, 37831, Oak Ridge, TN, USA;BioEnergy Science Center (BESC), Oak Ridge National Laboratory, One Bethel Valley Road, 37831, Oak Ridge, TN, USA;Bioprocess R&D, Dow AgroSciences, 9330 Zionsville Road, 46268, Indianapolis, IN, USA;

关键词: Avicel;    Differentially Express;    Crystalline Cellulose;    Clostridium Thermocellum;    Sugar Binding Protein;   

DOI  :  10.1186/1471-2180-11-134

 received in 2010-07-13, accepted in 2011-06-14,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe ability of Clostridium thermocellum ATCC 27405 wild-type strain to hydrolyze cellulose and ferment the degradation products directly to ethanol and other metabolic byproducts makes it an attractive candidate for consolidated bioprocessing of cellulosic biomass to biofuels. In this study, whole-genome microarrays were used to investigate the expression of C. thermocellum mRNA during growth on crystalline cellulose in controlled replicate batch fermentations.ResultsA time-series analysis of gene expression revealed changes in transcript levels of ~40% of genes (~1300 out of 3198 ORFs encoded in the genome) during transition from early-exponential to late-stationary phase. K-means clustering of genes with statistically significant changes in transcript levels identified six distinct clusters of temporal expression. Broadly, genes involved in energy production, translation, glycolysis and amino acid, nucleotide and coenzyme metabolism displayed a decreasing trend in gene expression as cells entered stationary phase. In comparison, genes involved in cell structure and motility, chemotaxis, signal transduction and transcription showed an increasing trend in gene expression. Hierarchical clustering of cellulosome-related genes highlighted temporal changes in composition of this multi-enzyme complex during batch growth on crystalline cellulose, with increased expression of several genes encoding hydrolytic enzymes involved in degradation of non-cellulosic substrates in stationary phase.ConclusionsOverall, the results suggest that under low substrate availability, growth slows due to decreased metabolic potential and C. thermocellum alters its gene expression to (i) modulate the composition of cellulosomes that are released into the environment with an increased proportion of enzymes than can efficiently degrade plant polysaccharides other than cellulose, (ii) enhance signal transduction and chemotaxis mechanisms perhaps to sense the oligosaccharide hydrolysis products, and nutrient gradients generated through the action of cell-free cellulosomes and, (iii) increase cellular motility for potentially orienting the cells' movement towards positive environmental signals leading to nutrient sources. Such a coordinated cellular strategy would increase its chances of survival in natural ecosystems where feast and famine conditions are frequently encountered.

【 授权许可】

Unknown   
© Raman et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.