RHS-elements function as type II toxin-antitoxin modules that regulate intra-macrophage replication of Salmonella...

Area of Science:

• Bacteriology
• Microbial Genetics
• Molecular Biology

Background:

• Rhs elements are widespread bacterial toxin-delivery systems under strong positive selection.
• The precise biological roles of Rhs toxins in bacteria remain largely uncharacterized.
• Salmonella Typhimurium possesses both full-length and orphan rhs genes.

Purpose of the Study:

• To investigate the function of Rhs toxin-antitoxin pairs in Salmonella Typhimurium.
• To determine how Rhs toxins influence bacterial proliferation within host macrophages.
• To elucidate the role of internal Rhs toxin expression in bacterial adaptation.

Main Methods:

• Genetic manipulation of Salmonella Typhimurium to create Rhs toxin mutants.
• In vitro culture of Salmonella Typhimurium within macrophage models.
• Quantification of bacterial proliferation and growth rates.

Main Results:

• Rhs toxin-antitoxin pairs function as type-II toxin-antitoxin loci.
• Mutant Salmonella Typhimurium lacking Rhs toxins exhibit twofold increased proliferation within macrophages.
• Enhanced proliferation is attributed to an increased bacterial growth rate.

Conclusions:

• Rhs toxins, beyond delivery, act as internal toxin-antitoxin systems regulating bacterial growth.
• These systems are crucial for Salmonella Typhimurium adaptation and proliferation in the stressful intracellular macrophage environment.
• Internal Rhs toxin-antitoxin expression provides a growth advantage, contributing to the strong positive selection of rhs loci.