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Live Cell Imaging of Bacillus subtilis and Streptococcus pneumoniae using Automated Time-lapse Microscopy
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Streptococcus pneumoniae synchronizes the states of cell wall peptidoglycan acetylation and genome methylation by

Xiu-Yuan Li1, Ping He1, Shaomeng Wang1

  • 1Center for Infection Biology, School of Basic Medical Sciences, Tsinghua University, Beijing, China.

Plos Pathogens
|August 5, 2025
PubMed

Insights

Bacterial N-acetylmuramic acid (NAM) O-acetylation acts as an extracellular signal, linking nutrient availability to bacterial lifestyle. This modification epigenetically controls Streptococcus pneumoniae colony phase via DNA methylation.

Area of Science:

  • Microbiology
  • Epigenetics
  • Bacterial Pathogenesis

Background:

  • Bacterial cell walls contain peptidoglycan (PG) with N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG).
  • NAM O-acetylation, a post-biosynthetic modification, enhances resistance to lysozyme but its functional significance remains unclear.
  • The extent of NAM O-acetylation varies with bacterial genetics and growth phase.

Purpose of the Study:

  • To investigate the functional role of NAM O-acetylation in Streptococcus pneumoniae.
  • To determine if NAM O-acetylation serves as an extracellular signal linking metabolism to bacterial phenotype.
  • To elucidate the mechanism by which NAM O-acetylation influences bacterial adaptation.

Main Methods:

  • Analysis of NAM O-acetylation levels in Streptococcus pneumoniae under varying nutrient conditions.
  • Investigation of the correlation between NAM O-acetylation and colony phase variation (opaque vs. transparent).
  • Assessment of DNA methyltransferase activity and genome methylation patterns (methylome) in relation to O-acetylation status.
  • Identification of bacterial proteins involved in mediating the O-acetylation-dependent epigenetic control.

Main Results:

  • NAM O-acetylation functions as an extracellular signal correlating with cellular acetyl-CoA levels and glucose availability.
  • O-acetylation controls reversible switching between opaque and transparent colony phases by modulating DNA methyltransferase gene inversion.
  • The presence of NAM O-acetylation leads to the HsdSA1 methylome and opaque colony phase, while its absence favors the HsdSA3 methylome and transparent phenotype.
  • Bacterial autolysin LytA and other proteins are essential for O-acetylation-mediated epigenetic regulation.

Conclusions:

  • Streptococcus pneumoniae utilizes NAM O-acetylation as an extracellular marker of cellular acetyl-CoA levels.
  • This modification epigenetically modulates bacterial metabolism and lifestyle in response to nutrient availability.
  • NAM O-acetylation synchronizes bacterial adaptation with environmental cues through epigenetic control of gene expression.

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