Abstract
Acinetobacter baumannii is known for its virulence in severely ill, hospitalized patients and for exhibiting multidrug resistance. A. baumannii infection treatment poses a serious problem in clinical environments. The outer membrane protein A (OmpA) of the Acinetobacter genus is involved in bacterial virulence. Regulatory factors of OmpA in the post-transcriptional stage have been previously identified. However, the regulatory factors that act before the transcriptional stage remain unclear. We investigated the A1S_0316 gene that encodes a putative transcription factor for OmpA expression in A. baumannii. A1S_0316 was purified and examined using size-exclusion chromatography, which revealed that it forms an oligomer. The binding affinity of A1S_0316 to the OmpA promoter region was also examined. We compared the binding affinity to the OmpA promotor region between A1S_0316 and the AbH-NS protein. A1S_0316 showed higher binding affinity to the OmpA promotor region than did H-NS. We examined the regulatory effect of these proteins on OmpA expression in A. baumannii using real-time qPCR and various in vitro tools. Our results indicated that A1S_0316 acts as an anti-repressor on the promotor region of the OmpA gene by inhibiting the binding of the AbH-NS protein. This study was the first demonstration of the transcriptional regulation of OmpA expression.
Highlights
Acinetobacter is a genus of strictly aerobic, Gram-negative coccobacillus that is part of the gammaproteobacteria class
A. baumannii exhibits resistance to many classes of antibiotics, including chloramphenicol, aminoglycosides, and fluoroquinolones [3]. It is one of the bacteria in the ESKAPE group of pathogens (i.e., Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), which are the major cause of nosocomial infections because of their strong antibiotic resistance [4]
To identify transcriptional factors that bound to the outer membrane protein A (OmpA) promoter region, the bacterial lysate was added to a DynabeadsTM M-280 Streptavidin-fused DNA mixture
Summary
Acinetobacter is a genus of strictly aerobic, Gram-negative coccobacillus that is part of the gammaproteobacteria class. A. baumannii exhibits resistance to many classes of antibiotics, including chloramphenicol, aminoglycosides, and fluoroquinolones [3] It is one of the bacteria in the ESKAPE group of pathogens (i.e., Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), which are the major cause of nosocomial infections because of their strong antibiotic resistance [4]. As the bacterial growth rate slows down, Hfq and MicA bind to the RBS, inhibiting the attachment of the ribosome complex to the OmpA mRNA [9]. This exposes the ss region, leading to RNA decay via RNase activity and the downregulation of OmpA [6]. We examined the possible pre-transcriptional regulators that interact with the promoter region of AbOmpA
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