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Impact of plfB delation on the transcriptome of Streptococcus pneumoniae D39

ABSTRACT: Galactose is an important sugar for in vivo survival and virulence of important human pathogen Streptococcus pneumoniae, and pyruvate formate lyase (PFL) activity is crucial for galactose metabolism. Thus, the regulation of genes important for active PFL synthesis, pflA and pflB, was investigated. We identified six transcriptional regulators differentially expressed in ΔpflB and hypothesised that they are important for pflA or pflB regulation. Among these, CcpA, MerR2 and GntR family transcriptional regulators were directly involved in the regulation of pflA, pflB or both. It was found that CcpA is the transcriptional activator of pflB, and is the repressor of pflA on galactose. CcpA’s interaction with pflB did not require HPr-[Ser-P] but is enhanced by sodium formate, produced by the activity of PFL. The MerR2 is a repressor of both pflA and pflB, and sodium formate decreases MerR2 affinity for pflB promoter. In addition, MerR2 mediates ccpA expression mainly on glucose and to lesser degree on galactose, and MerR2 and CcpA interact for regulation of pflB. It was shown that both CcpA and MerR2 are required for pneumococcal colonisation and virulence. We also found that GntR represses pflB expression but its expression is not induced by any of the tested sugars, suggesting sugar independent regulation of pflB.

ORGANISM(S): Streptococcus pneumoniae D39

PROVIDER: GSE67668 | GEO | 2017/01/26

SECONDARY ACCESSION(S): PRJNA280604

REPOSITORIES: GEO

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Project description:Cytosolic acetyl-coenzyme A is a precursor for many biotechnologically relevant compounds produced by Saccharomyces cerevisiae. In this yeast, cytosolic acetyl-CoA synthesis and growth strictly depend on expression of either the Acs1 or Acs2 isoenzyme of acetyl-CoA synthetase (ACS). Since hydrolysis of ATP to AMP and pyrophosphate in the ACS reaction constrains maximum yields of acetyl-CoA-derived products, this study explores replacement of ACS by two ATP-independent pathways for acetyl-CoA synthesis. After evaluating expression of different bacterial genes encoding acetylating acetaldehyde dehydrogenase (A-ALD) and pyruvate-formate lyase (PFL), acs1M-NM-^T acs2M-NM-^T S. cerevisiae strains were constructed in which A-ALD or PFL successfully replaced ACS. In A-ALD-dependent strains, aerobic growth rates of up to 0.27 h-1 were observed, while anaerobic growth rates of PFL-dependent S. cerevisiae (0.21 h-1) were stoichiometrically coupled to formate production. In glucose-limited chemostat cultures, intracellular metabolite analysis did not reveal major differences between A-ALD-dependent and reference strains. However, biomass yields on glucose of A-ALD- and PFL-dependent strains were lower than those of the reference strain. Transcriptome analysis suggested that reduced biomass yields were caused by acetaldehyde and formate in A-ALD- and PFL-dependent strains, respectively. Transcript profiles also indicated that a previously proposed role of Acs2 in histone acetylation is probably linked to cytosolic acetyl-CoA levels rather than to direct involvement of Acs2 in histone acetylation. While, for the first time, demonstrating that yeast ACS can be fully replaced by alternative reactions, this study demonstrates that further modifications are needed to achieve optimal in vivo efficiencies of the supply of acetyl-CoA as product precursor. To investigate the impact of introduced changes in native pathway of cytosolic acetyl-CoA formation in S. cerevisiae, a DNA microarray-based transcriptome analysis was performed on aerobic or anaerobic, glucose-limited chemostat cultures.

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Impact of plfB delation on the transcriptome of Streptococcus pneumoniae D39

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