Transcription profiling by array to study the response of Clostridium acetobutylicum to iron limitation and inactivation of ferric uptake regulator (fur)
ABSTRACT: Clostridium acetobutylicum is a Gram-positive, endospore-forming bacterium that is considered as a strict anaerobe. It ferments sugars to the organic acids acetate and butyrate or shifts to formation of the solvents - ethanol, butanol and acetone. In most bacteria the major regulator of iron homeostasis is Fur (ferric uptake regulator). Analysis of the genome of Clostridium acetobutylicum has revealed three genes encoding Fur-like proteins. The amino acid sequece of one of them showed 70% similarity to the Fur protein of the closely related Bacillus subtilis. Thus, to gain insight into the role of Fur and the mechanisms for maintenance of iron homeostasis in this strict anaerobic organism, we determined its transcriptional profile in response to iron limitation and inactivation of fur.
Project description:Clostridium acetobutylicum is well-known for its butanol production. Butanol toxicity is a major drawback for the generation of high-butanol producing strains. Here, the transcriptional response a steady state, acidogenic (pH 6), phosphate-limited Clostridium acetobutylicum chemostat culture to different levels of n-butanol (0.25-1%) was investigated. For the butanol challenge experiments butanol (1-butanol) was added (a) to the supplying medium and (b) to the culture vessel to guarantee an immediate change in the butanol concentration. Addition of butanol to the culture was timed to match the supply of the new medium through the feedlines. The butanol concentration was increased stepwise in intervals of 66.6 h (5 volume changes) to moderate butanol concentrations of 0.25%, 0.5%, 0.75% and 1% (v/v).
Project description:In this study the transcriptional behavior of the natural solvent producing bacterium Clostridium acetobutylicum was investigated following n butanol stress using DNA microarray analysis. Therefore, a phosphate-limited chemostat culture was established and n-butanol stress (0.9%) was added to acidogenic cells at pH 5.7.
Project description:In this study the transcriptional behavior of the natural solvent producing bacterium Clostridium acetobutylicum was investigated following n-butanol stress using DNA microarray analysis. Therefore, a phosphate-limited chemostat culture was established and n-butanol stress (0.9%) was added to acidogenic cells at pH 5.7.
Project description:Clostridium acetobutylicum is characterized by its acetone-butanol (AB) fermentation which <br>can be reproducibly established under continuous grow conditions in a chemostat. <br>At pH 5.7 cells show typical acidogenic metabolism and mainly produce the acids <br>acetate and butyrate. After lowering and further control the external pH at 4.5 <br>the exponentially growing cells switch towards stable solvent production with the <br>dominating fermentation products acetone and butanol. <br>Here we present a comprehensive comparison of proteome and transcriptome <br>data of continuously growing cells of C. acetobutylicum in a chemostat culture <br>under phosphate limitation at pH 5.7 (acidogenesis) and pH 4.5 (solventogenesis).
Project description:Artificial electron carriers have been widely used to shift the solvent ratio towards butanol in acetone-butanol-ethanol (ABE) fermentation of solventogenic clostridia according to decreased hydrogen production. In this study, first insights on the molecular level were gained to explore the effect of methyl viologen addition to cultures of Clostridium acetobutylicum. Employing batch fermentation in mineral salts medium, the butanol:acetone ratio was successively increased from 2.3 to 12.4 on a 100 ml scale in serum bottles and from 1.4 to 16.5 on a 1,300 ml scale in bioreactors, respectively. The latter cultures were used for DNA microarray analyses to provide new information on the transcriptional changes referring to methyl viologen exposure and thus, exhibing gene expression patterns according to the manipulation of the cellular redox balance.
Project description:Clostridium acetobutylicum was grown in a batch-culture with minimal medium containing glucose and xylose as substrate. Diauxie growth was observed after glucose was consumed. Following the organism grows on xylose. Transcriptional analysis was done to pursue the cellular processes during the switch from growth on glucose to growth on xylose. We compared DNA-Microarray data from cells grown during the exponential phase on glucose (A), with cells growing during the start of diauxie growth lag (B), during the end of diauxie growth lag (C) and during exponential growth on xylose (D). We used cells grown in a continuous culture with glucose as substrate as common reference for the samples A-D.
Project description:MYB10 and MYB72 are two transcription factors expressed in Arabidopsis roots under iron deficiency. To understand the contribution of these factors, we analyzed gene expression in roots of wild-type (Col) and mutant (myb10myb72 double knockout) seedlings exposed to iron deficiency for 72 hours.
Project description:V. vulnificus is a marine bacteria that causes diseases in both mammals and fish. In both hosts, the iron concentration represents a key factor that greatly influences the virulence of this bacterium. To further define the gene repertoire that is regulated by iron concentration and Fur protein (the main transcriptional regulator in response to iron concentration) in V. vulnificus, we obtained a mutant in Fur and used DNA microarray technology to monitor the expression of the entire gene repertoire in response to iron. Global transcriptomic response was reconstructed by comparing the transcriptional profiles of the wild-type (R99) and Fur mutant strains in poor and rich iron conditions. To identify the genes that were under control of Fur, we compared the transcriptomic profile of the wild-type strain with the profile of a mutant strain in Fur protein; in contrast, to identify the genes that were under control of iron, we compared the transcriptomic profile of the wild-type strain grown in iron-rich conditions with the profile of the wild-type strain grown in iron-restricted conditions. For each one of the four samples, three replicates were performed, and RNA was sampled in the mid-log phase of growth (wild-type, 6h; Fur mutant, 6h; wild-type+iron, 5h; wild-type-iron,9h).