Physiological Roles of an Acinetobacter-specific σ Factor.

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Acinetobacter baumannii is a critical antibiotic-resistant pathogen.
• Extracytoplasmic function (ECF) sigma factors regulate stress responses in bacteria.
• The role of SigAb, an ECF sigma factor in A. baumannii, remains poorly understood.

Purpose of the Study:

• To characterize the SigAb regulon and its physiological role in A. baumannii.
• To investigate SigAb's involvement in metal stress response.
• To identify novel genes and regulatory mechanisms controlled by SigAb.

Main Methods:

• Promoter mutagenesis, motif scanning, and ChIP-seq to define the direct SigAb regulon.
• RNA-seq to identify the indirect SigAb regulon.
• CRISPRi and Tn-seq approaches to assess gene function and fitness.

Main Results:

• SigAb is a metal stress-responsive ECF sigma factor unique to Acinetobacter.
• The direct SigAb regulon includes sigAb, relA, and the small RNA sabS.
• SigAb controls metal resistance genes and is essential for A. baumannii fitness, with aabA and aabB exhibiting anti-SigAb activity.

Conclusions:

• SigAb plays a distinct role in Acinetobacter stress response and homeostasis, differing from RpoE.
• SigAb and its associated genes (sabS, aabA, aabB) are crucial for bacterial fitness.
• This research provides insights into A. baumannii's regulatory architecture and identifies potential therapeutic targets.