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Microcystis aeruginosa msoT1/msoA1 Locus Displays Features of a Type I Toxin-Antitoxin System

Matija Ruparčič1, Marko Dolinar1

  • 1Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia.

Toxins
|August 27, 2025
PubMed

Insights

Type I toxin-antitoxin systems were found in Cyanobacteria. The MsoT1 toxin inhibits cell growth, but its antitoxin MsoA1 neutralizes this effect, identifying a novel system.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Type I toxin-antitoxin (TA) systems are crucial for bacterial genetic stability.
  • These systems, comprising a toxin and an antitoxin, are well-documented in Proteobacteria, Firmicutes, and Tenericutes.
  • Their presence in Cyanobacteria remained unexplored.

Purpose of the Study:

  • To investigate the potential presence of type I TA systems in Cyanobacteria.
  • To identify and characterize novel type I TA systems in *Microcystis aeruginosa*.

Main Methods:

  • Bioinformatic analysis of the *Microcystis aeruginosa* PCC 7806SL genome.
  • Experimental characterization of putative type I TA loci in *Escherichia coli*.
  • Confirmation of gene expression and functional interaction between toxin and antitoxin.

Main Results:

  • Ten putative type I TA loci were identified in the *M. aeruginosa* genome.
  • Two toxins, BH695_0320 and MsoT1, exhibited inhibitory effects on *E. coli* cell growth.
  • The MsoT1/MsoA1 system demonstrated toxin-antitoxin activity, with MsoA1 neutralizing MsoT1's toxicity.

Conclusions:

  • The MsoT1/MsoA1 system represents a novel type I TA system.
  • This discovery marks the first identification of a type I TA system in the Cyanobacteria phylum.
  • These findings expand the known diversity of TA systems in prokaryotes.
Keywords:
Microcystis aeruginosabacterial toxinscyanobacterianovel toxin–antitoxin systemstype I toxin–antitoxin systems

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