Transcription of the pst Operon of Clostridium acetobutylicum Is Dependent on Phosphate Concentration and pH

Abstract

The pst operon of Clostridium acetobutylicum ATCC 824 comprises five genes, pstS, pstC, pstA, pstB, and phoU, and shows a gene architecture identical to that of Escherichia coli. Deduced proteins are predicted to represent a high-affinity phosphate-specific ABC (ATP-binding cassette) transport system (Pst) and a protein homologous to PhoU, a negative phosphate regulon regulator. We analyzed the expression patterns of the pst operon in P i -limited chemostat cultures during acid production at pH 5.8 or solvent production at pH 4.5 and in response to P i pulses. Specific mRNA transcripts were found only when external P i concentrations had dropped below 0.2 mM. Two specific transcripts were detected, a 4.7-kb polycistronic mRNA spanning the whole operon and a quantitatively dominating 1.2-kb mRNA representing the first gene, pstS. The mRNA levels clearly differed depending on the external pH. The amounts of the full-length mRNA detected were about two times higher at pH 5.8 than at pH 4.5. The level of pstS mRNA increased by a factor of at least 8 at pH 5.8 compared to pH 4.5 results. Primer extension experiments revealed only one putative transcription start point 80 nucleotides upstream of pstS. Thus, additional regulatory sites are proposed in the promoter region, integrating two different extracellular signals, namely, depletion of inorganic phosphate and the pH of the environment. After phosphate pulses were applied to a phosphate-limited chemostat we observed faster phosphate consumption at pH 5.8 than at pH 4.5, although higher optical densities were recorded at pH 4.5.

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

“…It is part of a predicted operon, which also includes phoU (GSU1095), pstA (GSU1097), pstC (GSU1098) and pstS (GSU1099). pstA, pstC and pstS were also upregulated and are annotated to have a role in phosphate uptake, whereas phoU is predicted to regulate the expression of the pst genes (Table 2), consistent with similar operon organization of related genes in other microorganisms (Nakata et al, 1984;Nikata et al, 1996;VanBogelen et al, 1996;Bardin and Finan, 1998;Aguena et al, 2002;Fischer et al, 2006). The pst-pho operon was previously shown to be the most strongly up-regulated operon under phosphatelimiting conditions in S. meliloti (Krol and Becker, 2004) and Acidothiobacillus ferroxidans (Vera et al, 2003;Krol and Becker, 2004).…”

“…In other microorganisms, such as Bacillus subtilis, Clostridium acetobutylicum, Escherichia coli or Pseudomonas aeruginosa, phosphate-limiting conditions are associated with increased expression of genes in the pst-pho operon, which encode genes associated with a high-affinity phosphate uptake system (Nakata et al, 1984;Nikata et al, 1996;VanBogelen et al, 1996;Aguena et al, 2002;Allenby et al, 2004;Fischer et al, 2006). All of the available Geobacter species genomes contain at least one copy of the pstpho operon, suggesting that organisms in this genus share this high-affinity uptake system.…”

Increased productivity of Clostridium acetobutylicum fermentation of acetone, butanol, and ethanol by pervaporation through supported ionic liquid membrane

“…acetobutylicum ATCC 824 (laboratory collection; Prof. Hubert Bahl, University of Rostock) was grown under anaerobic phosphate-limited conditions in a Biostat B 1.5-l fermenter system (BBI, Melsungen, Germany) at 37°C, pH 4.5, and 200 rpm with 4 (wt%) glucose in the minimal medium (Bahl et al 1982a, b) of the supplying vessel (Fischer et al 2006). For the generation of a continuing butan-1-ol surplus, a sterile solution of butan-1-ol (analytical grade; Sigma Aldrich, Germany) was injected into the supplying vessel up to concentrations of 5, 10, 15, and 18 g/l.…”

“…Optical density (OD-bacteria quantity) at 600 nm and phosphate concentration were measured in accordance with previous description by Fischer et al (2006). The OD was determined in a spectrophotometer (Spekol 1100 photometer; Analytic Jena, Jena, Germany) using a plastic cuvette with a light path of 1 cm.…”

“…Due to the oil crisis of the seventies, an emerging scarcity of the oil resources, and an associated increase of the oil prices, the clostridial ABEfermentation received attention again (Dürre 2005a, b). A lot of work was done for better understanding of the molecular mechanisms of the solvent production (Qureshi and Maddox 2005;Fischer et al 2006;Cornillot et al 1997;Dürre 2005a, b) as well as the optimization of it (Dürre 2005a, b). Therefore, it could be shown that the growth of C. acetobutylicum in a chemostat culture with an excess of glucose, a pH below 5, and a limitation of phosphate led to the highest glucose consumption and product concentration over a long period of time (Bahl et al 1982a, b;Bahl and Gottschalk 1984).…”