Regulation of pneumococcal epigenetic and colony phases by multiple two-component regulatory systems

PLoS Pathog. 2020 Mar 18;16(3):e1008417. doi: 10.1371/journal.ppat.1008417. eCollection 2020 Mar.

Abstract

Streptococcus pneumoniae is well known for phase variation between opaque (O) and transparent (T) colonies within clonal populations. While the O variant is specialized in invasive infection (with a thicker capsule and higher resistance to host clearance), the T counterpart possesses a relatively thinner capsule and thereby higher airway adherence and colonization. Our previous study found that phase variation is caused by reversible switches of the "opaque ON-or-OFF" methylomes or methylation patterns of pneumococcal genome, which is dominantly driven by the PsrA-catalyzed inversions of the DNA methyltransferase hsdS genes. This study revealed that switch frequency between the O and T variants is regulated by five transcriptional response regulators (rr) of the two-component systems (TCSs). The mutants of rr06, rr08, rr09, rr11 and rr14 produced significantly fewer O and more T colonies. Further mutagenesis revealed that RR06, RR08, RR09 and RR11 enrich the O variant by modulating the directions of the PsrA-catalyzed inversion reactions. In contrast, the impact of RR14 (RitR) on phase variation is independent of PsrA. Consistently, SMRT sequencing uncovered significantly diminished "opaque ON" methylome in the mutants of rr06, rr08, rr09 and rr11 but not that of rr14. Lastly, the phosphorylated form of RR11 was shown to activate the transcription of comW and two sugar utilization systems that are necessary for maintenance of the "opaque ON" genotype and phenotype. This work has thus uncovered multiple novel mechanisms that balance pneumococcal epigenetic status and physiology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins* / genetics
  • Bacterial Proteins* / metabolism
  • DNA Methylation*
  • DNA Restriction-Modification Enzymes* / genetics
  • DNA Restriction-Modification Enzymes* / metabolism
  • DNA, Bacterial* / genetics
  • DNA, Bacterial* / metabolism
  • Epigenesis, Genetic*
  • Gene Expression Regulation, Bacterial*
  • Genome, Bacterial*
  • Streptococcus pneumoniae* / genetics
  • Streptococcus pneumoniae* / metabolism

Substances

  • Bacterial Proteins
  • DNA Restriction-Modification Enzymes
  • DNA, Bacterial
  • HSDS protein, Bacteria

Grants and funding

This work was supported by grants from National Natural Science Foundation of China (numbers 31530082, 31820103001, 81671972 and 31728002). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.