Acinetobacter baumannii represses type VI secretion system through a manganese-dependent small RNA-mediated...

Area of Science:

• Bacterial molecular biology
• Microbial pathogenesis
• Gene regulation

Background:

• The Type VI Secretion System (T6SS) is crucial for bacterial competition and host cell manipulation by Gram-negative bacteria.
• Acinetobacter baumannii utilizes T6SS, often leading to the loss of the pAB3 plasmid and its associated antibiotic resistance.
• The regulatory mechanisms governing T6SS in A. baumannii are not fully understood.

Purpose of the Study:

• To elucidate the regulatory network controlling the T6SS in Acinetobacter baumannii.
• To identify the role of small RNAs in T6SS regulation.
• To investigate the influence of manganese (Mn2+) on T6SS activity.

Main Methods:

• Identification and characterization of the small RNA AbsR28.
• Analysis of Mn2+ uptake via the MumT transporter.
• Investigation of AbsR28-mediated post-transcriptional regulation of the tssM mRNA.
• Assessment of RNase E's role in mRNA degradation and T6SS repression.

Main Results:

• AbsR28 acts as a manganese (Mn2+)-dependent regulator of T6SS.
• Intracellular Mn2+ abundance promotes AbsR28 binding to tssM mRNA, leading to its degradation by RNase E.
• This process results in the repression of T6SS and maintains the integrity of the pAB3 plasmid.

Conclusions:

• AbsR28 mediates a novel crosstalk between Mn2+ homeostasis and T6SS regulation in A. baumannii.
• This sRNA-based mechanism allows bacteria to retain antibiotic resistance by inactivating T6SS.
• The findings provide insights into bacterial adaptation strategies during infection.