Minimalistic mycoplasmas harbor different functional toxin-antitoxin systems

Area of Science:

• Microbiology
• Bacterial Genetics
• Molecular Biology

Background:

• Mycoplasmas are small bacteria causing chronic diseases and contributing to antimicrobial resistance.
• Virulence factors in mycoplasmas, particularly those promoting persistence, are poorly understood.
• Toxin-antitoxin (TA) systems are known bacterial persistence factors, but their presence in mycoplasmas is largely uncharacterized.

Purpose of the Study:

• To investigate the presence and function of candidate toxin-antitoxin (TA) systems in Mycoplasma mycoides subsp. capri.
• To assess the role of TA systems in mycoplasma persistence and explore their potential applications.
• To confirm the functionality of TA systems in other mycoplasma species.

Main Methods:

• Genome sequencing of 14 M. mycoides subsp. capri strains to identify TA systems.
• Transcriptomic and proteomic analyses to study TA system expression.
• Functional validation of candidate TA systems using heterologous expression in M. capricolum subsp. capricolum.
• Investigation of TA system homologs in other mycoplasma phylogenetic groups.

Main Results:

• Confirmed the presence of at least one TA system in all sequenced M. mycoides subsp. capri genomes, including novel AAA-ATPase/subtilisin-like protease and AbiE/Fic-RelB pairs.
• Identified signatures of horizontal gene transfer associated with TA systems in several mycoplasma species.
• Demonstrated the functionality of three candidate TA systems in M. capricolum subsp. capri, confirming their role in neutralization and persistence.
• Confirmed functional TA system homologs in Hominis and Pneumoniae mycoplasma groups.
• Showcased the potential of M. mycoides subsp. capri toxins, especially the subtilisin-like serine protease, for developing a mycoplasma kill switch.

Conclusions:

• Toxin-antitoxin systems are prevalent in Mycoplasma mycoides subsp. capri and likely contribute to bacterial persistence.
• Horizontal gene transfer plays a role in the distribution of TA systems among mycoplasma species.
• The identified TA systems are functional and can be validated in related mycoplasma hosts.
• Mycoplasma TA systems, particularly specific toxins, offer promising avenues for biotechnological applications like kill switches.