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A Fast and Reliable Pipeline for Bacterial Transcriptome Analysis Case study: Serine-dependent Gene Regulation in Streptococcus pneumoniae
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Identification and Characterization of Negative Regulators of Rgg1518 Quorum Sensing in Streptococcus pneumoniae
Duoyi Hu1, Irina Laczkovich2, Michael J Federle3,4
1Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
Journal of Bacteriology
|June 21, 2023
Summary
Streptococcus pneumoniae uses quorum sensing (QS) for communication. We found that PepO enzyme degrades SHP1518, inhibiting Rgg/SHP1518 QS signaling, revealing a key mechanism in pneumococcal virulence regulation.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Streptococcus pneumoniae causes significant human diseases, including pneumonia, meningitis, and otitis media.
- Quorum sensing (QS) is a critical intercellular communication mechanism in S. pneumoniae, regulating gene expression and virulence.
- The Rgg/SHP1518 QS system is one of several identified in S. pneumoniae, but its regulatory network and fitness contributions require further elucidation.
Purpose of the Study:
- To investigate the regulatory activities of Rgg paralogs in the D39 genome.
- To understand the convergent regulation of the spd_1513-1517 operon.
- To identify upstream regulators of the Rgg/SHP1518 QS system.
Main Methods:
- Transcriptomic analysis of six QS regulator mutants.
- Transposon mutagenesis screening to identify upstream regulators.
- Enzyme activity assays and site-directed mutagenesis to characterize PepO function.
Main Results:
- At least four QS regulators influence the expression of the spd_1513-1517 operon, controlled by Rgg/SHP1518.
- Transposon insertions in pepO and spxB mutants led to increased Rgg1518-dependent transcription.
- Pneumococcal PepO was identified as a metalloendopeptidase that degrades SHP1518, inhibiting Rgg/SHP1518 QS activation, with a critical role for a glutamic acid residue in its catalytic domain.
Conclusions:
- Multiple Rgg regulators converge on controlling the Rgg/SHP1518 QS system.
- PepO acts as a negative regulator of Rgg/SHP1518 QS by degrading its signaling molecule.
- This study elucidates a novel mechanism of QS regulation in S. pneumoniae, highlighting PepO's role in controlling virulence factor expression.
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