Pneumococcal galactose catabolism is controlled by multiple regulators acting on pyruvate formate lyase

Firas A Y Al-Bayati,Hasan F H Kahya,Andreas Damianou,Sulman Shafeeq,Hasan Yesilkaya,Peter W Andrew,Oscar P Kuipers

doi:10.1038/srep43587

Firas A Y Al-Bayati, Hasan F H Kahya + Show 5 more

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https://doi.org/10.1038/srep43587

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Abstract

Catabolism of galactose by Streptococcus pneumoniae alters the microbe’s metabolism from homolactic to mixed acid fermentation, and this shift is linked to the microbe’s virulence. However, the genetic basis of this switch is unknown. Pyruvate formate lyase (PFL) is a crucial enzyme for mixed acid fermentation. Functional PFL requires the activities of two enzymes: pyruvate formate lyase activating enzyme (coded by pflA) and pyruvate formate lyase (coded by pflB). To understand the genetic basis of mixed acid fermentation, transcriptional regulation of pflA and pflB was studied. By microarray analysis of ΔpflB, differential regulation of several transcriptional regulators were identified, and CcpA, and GlnR’s role in active PFL synthesis was studied in detail as these regulators directly interact with the putative promoters of both pflA and pflB, their mutation attenuated pneumococcal growth, and their expression was induced on host-derived sugars, indicating that these regulators have a role in sugar metabolism, and multiple regulators are involved in active PFL synthesis. We also found that the influence of each regulator on pflA and pflB expression was distinct in terms of activation and repression, and environmental condition. These results show that active PFL synthesis is finely tuned, and feed-back inhibition and activation are involved.

Highlights

The notable gene classes with differential expression were consistent with pyruvate formate lyase (PFL)’s role in galactose metabolism, pyruvate dissimilation, and catabolic and anabolic reactions, and included those coding for galactose hydrolysis and sugar uptake (n = 27), genes implicated in cell shape (n = 6), and fatty acid biosynthesis and acetate dissimilation (n = 13)
Pyruvate formate lyase is a key enzyme for pyruvate dissimilation in S. pneumoniae
Very little was known about the transcriptional regulation of genes involved in active PFL synthesis

Summary

Introduction

(PFL)[2,9]. The formation of acetyl-CoA gives the possibility of formation of an additional ATP via the action of acetate kinase or regeneration of two molecules of NAD+ with the formation of ethanol. We show that utilization of galactose leads to the generation of mixed acids, and that pyruvate formate lyase (PFL), converting pyruvate to formate and acetyl-CoA, is the key enzyme for mixed acid fermentation[2]. Mutation of either pflB, which codes for PFL, or pflA, which codes for the pyruvate formate lyase activating enzyme (PFL-AE), being responsible for posttranslational activation of inactive PFL, results in abrogation of mixed acid fermentation on galactose, and interestingly leads to a decrease in pneumococcal virulence[2]. We gathered evidence showing that some of these regulators are induced by galactose, their control over pflA and pflB is influenced by sodium formate, they exert regulatory influence on each other, and are required for pneumococcal colonization and virulence

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