Transcriptional Analysis of Clostridium beijerinckii NCIMB 8052 and the Hyper-Butanol-Producing Mutant BA101 during the Shift from Acidogenesis to Solventogenesis

Abstract

Clostridium beijerinckii is an anaerobic bacterium used for the fermentative production of acetone and butanol. The recent availability of genomic sequence information for C. beijerinckii NCIMB 8052 has allowed for an examination of gene expression during the shift from acidogenesis to solventogenesis over the time course of a batch fermentation using a ca. 500-gene set DNA microarray. The microarray was constructed using a collection of genes which are orthologs of members of gene families previously found to be important to the physiology of C. acetobutylicum ATCC 824. Similar to the onset of solventogenesis in C. acetobutylicum 824, the onset of solventogenesis in C. beijerinckii 8052 was concurrent with the initiation of sporulation. However, forespores and endospores developed more rapidly in C. beijerinckii 8052 than in C. acetobutylicum 824, consistent with the accelerated expression of the sigE-and sigG-regulated genes in C. beijerinckii 8052. The comparison of gene expression patterns and morphological changes in C. beijerinckii 8052 and the hyperbutanol-producing C. beijerinckii strain BA101 indicated that BA101 was less efficient in sporulation and phosphotransferase system-mediated sugar transport than 8052 but that it exhibited elevated expression of several primary metabolic genes and chemotaxis/motility genes.The gram-positive, spore-forming, anaerobic clostridia constitute a diverse group of species with industrial, agricultural, and medical relevance. Clostridium acetobutylicum and C. beijerinckii are among the prominent solventogenic species capable of acetone and butanol formation via fermentation (8,15). Butanol is widely used as an industrial chemical. Butanol also exhibits a range of physical properties, including high energy content, water immiscibility, low vapor pressure, and octaneenhancing power, which provide it with potential as a liquid fuel (17). Developing fermentation processes based on the solventogenic clostridia offers the prospect of butanol production from agricultural feedstocks as an alternative to the petrochemical route (8). Much of past efforts has been focused on C. acetobutylicum ATCC 824 (1,16,23). However, the functional characterization of genes and metabolic pathways remains to be undertaken. Recently, genome sequencing of C. beijerinckii NCIMB 8052 was completed by the Joint Genome Institute of the Department of Energy. This accomplishment opens up the exciting possibility of investigating the molecular mechanism of solventogenesis on a genome scale. The objective of this study involves using DNA microarray analysis to examine gene expression in relation to physiological changes associated with C. beijerinckii solvent production and cell growth and differentiation. The comparison of gene expression patterns in the C. beijerinckii 8052 parental strain and the C. beijerinckii BA101 hyper-butanol-producing mutant strain (3, 11) will provide insights toward engineering genetically modified C. beijerinckii strains with improved butanol yields, titers, and productivity...

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