A proteomic and transcriptional view of acidogenic and solventogenic steady-state cells of Clostridium acetobutylicum in a chemostat culture

SysMO is a European transnational funding and research initiative on "Systems Biology of Microorganisms".

The goal pursued by SysMO was to record and describe the dynamic molecular processes going on in unicellular microorganisms in a comprehensive way and to present these processes in the form of computerized mathematical models.

Systems biology will raise biomedical and biotechnological research to a new quality level and contribute markedly to progress in understanding. Pooling European research ...

Systems Biology of Clostridium acetobutylicum - a possible answer to dwindling crude oil reserves

Comparison of the transcriptome at steady state in acidogenesis and at steady state in solventogenesis.

Investigation of all steady state pH-values between pH 5.7 and 4.5 (pH 5.5, 5.3, 5.1, 4.9, 4.7).

Measurements of acetone, butanol, acetate, butyrate and ethanol taken during dynamic shift (pH 5.8, 5.5, 5.3, 5.1, 4.9, 4.7, 4.5) and at steady state (pH 5.7, 5.5, 5.3, 5.1, 4.9, 4.7, 4.5).

Monitoring of end products ethanol, acetone, butanol, acetate and butyrate during master fermentation of Clostridium acetobutylicum at the steady state pH values 5.5, 5.3, 5.1, 4.9 and 4.7.

Micro array analysis of steady-state growing cells of Clostridium acetobutylicum at pH 5.7 (acidogenesis) in comparison to pH 4.5 (solventogenesis).

Monitoring of end products in mM of ethanol, acetone, butanol, acetate and butyrate during master fermentation of Clostridium acetobutylicum at the steady state pH values 5.7 (acidogenesis) and 4.5 (solventogenesis).

Micro array analyses of all mRNA levels of cells growing at steady state pH values 5.7, 5.5, 5.3, 5.1, 4.9, 4.7 compared to the same reference steady-state pH 4.5.

All spots and identified proteins of Clostridium acetobutylicum growing at steady-state pH 5.7 (acidogenesis) and pH 4.5 (solventogenesis), respectively, using 2D PAGE and Maldi-TOF analysis. The focus were cytosolic proteins with an isoelectric point bewteen 4 and 7 as well as a molecular weight of 180-10 kDa.

Representation of all prepared 2D PAGE analyses of cytosolic proteins of Clostridium acetobutylicum growing continuously at pH 5.5, 5.3, 5.1, 4.9 and 4.7.

This model assumes a phenotypic switch between an acid- and solvent-forming population caused by the changing pH levels. The two phenotypes differ in their transcriptomic, proteomic, and ,thus, their metabolomic profile. Because the growth rates of these phenotypes depends on the extracellular pH, the initiation of the pH-shift results in a significant decline of the acidogenic population. Simultaneously, the solvent-forming population rises and establishes an new steady state.

The model is build ...

The acetone-butanol-ethanol (ABE) fermentation of Clostridium acetobutylicum attracts new attention because it provides a potential alternative for the synthesis of value added chemicals to petroleum and other fossil reserves. This fermentative metabolic process comprises two distinct metabolic states that differ in their product spectrum. Growing on starch or sugars the predominant fermentation products are acetate and butyrate during acidogenesis (high pH). In contrast, C. acetobutylicum produces ...

This presentation given at the 5th International Beilstein Symposium presents the development of a model for the pH-induced shift in C. acetobutylicum. Starting from experimental information, the model construction and underlying assumptions are explained. Furthermore, the required additions to the metabolic and genetic network caused by the used experimentals setup are established.

The established metabolic and genetic model is compared to dynamic shift experiments starting at acidogenesis and ...