Maltose-Dependent Transcriptional Regulation of the mal Regulon by MalR in Streptococcus pneumoniae.

Muhammad Afzal,Sulman Shafeeq,Oscar P Kuipers,Irfan Manzoor,Willem Van Schaik

doi:10.1371/journal.pone.0127579

Muhammad Afzal, Sulman Shafeeq + Show 3 more

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https://doi.org/10.1371/journal.pone.0127579

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Abstract

The maltose regulon (mal regulon) has previously been shown to consist of the mal gene cluster (malMP, malXCD and malAR operons) in Streptococcus pneumoniae. In this study, we have further elucidated the complete mal regulon in S. pneumoniae D39 using microarray analyses and β-galactosidase assays. In addition to the mal gene cluster, the complete mal regulon of S. pneumoniae D39 consists of a pullulanase (PulA), a glucosidase (DexB), a glucokinase (RokB), a PTS component (PtsG) and an amylase (AmyA2). Our microarray studies and β-galactosidase assays further showed that the LacI-family transcriptional regulator MalR represses the expression of the mal regulon in the absence of maltose. Furthermore, the role of the pleiotropic transcriptional regulator CcpA in the regulation of the mal regulon in the presence of maltose was explored. Our microarray analysis with a ΔccpA strain showed that CcpA only represses the expression of the malXCD operon and the pulA gene in the presence of maltose. Hence, we extend the mal regulon now consisting of pulA, dexB, rokB, ptsG and amyA2 in addition to malMP, malXCD and malAR operons.

Highlights

Streptococcus pneumoniae is a Gram-positive, alpha-hemolytic, facultative anaerobic member of the genus Streptococcus and a significant human pathogen [1]
The studies on maltose regulation in S. pneumoniae have so far shown only the mal gene cluster as a part of the mal regulon, whereas in this study we have explored the maltose-mediated gene regulation through microarray studies and β-galactosidase assays, and identified the complete mal regulon regulated by the transcriptional repressor MalR in S. pneumoniae
M17 broth [19] supplemented with 0.5% (w/v) glucose was used for growing S. pneumoniae D39 [20] in tubes or on blood agar plates supplemented with 1% (v/v) defibrinated sheep blood in micro-aerophilic conditions at 37°C

Summary

Introduction

Streptococcus pneumoniae is a Gram-positive, alpha-hemolytic, facultative anaerobic member of the genus Streptococcus and a significant human pathogen [1]. It is present in the nasopharynx asymptomatically and may spread to various parts of the human body to cause numerous diseases including pneumonia, meningitis, septicemia and otitis media [2,3]. For successful survival and pathogenesis, it needs to acclimatize itself to changing nutritional circumstances inside the human body and make use of the available resources Among these resources, carbohydrates are of utmost utility for pneumococcus, as it uses them as a carbon source for growth and survival [4]. Regulatory mechanisms of different sugars and carbon sources have been studied in S. pneumoniae [5,6,7,8,9,10,11].

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