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Sigma's Non-specific Protease Activity Assay - Casein as a Substrate
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Implication of the σ

Ren-Hsuan Ku1, Li-Hua Li2,3, Yi-Fu Liu1

  • 1Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.

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|June 7, 2023
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Summary
This summary is machine-generated.

Loss of Stenotrophomonas maltophilia

Keywords:
OmpARpoNouter membrane proteinssigma factor

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Area of Science:

  • Bacterial outer membrane protein structure and function
  • Microbial stress response mechanisms
  • Genomic and transcriptomic analysis in bacteria

Background:

  • Outer membrane protein A (OmpA) is vital for bacterial cell envelope integrity.
  • A Stenotrophomonas maltophilia mutant lacking the OmpA C-terminal domain (KJΔOmpA299-356) shows reduced tolerance to oxidative stress.
  • The precise mechanism behind this decreased tolerance remains to be fully elucidated.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying the reduced menadione-mediated oxidative stress tolerance in the Stenotrophomonas maltophilia KJΔOmpA299-356 mutant.
  • To identify key genes and regulatory factors involved in the stress response pathway affected by OmpA C-terminal domain loss.
  • To elucidate the regulatory circuit connecting OmpA function, σ factor activity, and oxidative stress tolerance.

Main Methods:

  • Comparative transcriptome analysis of wild-type and KJΔOmpA299-356 Stenotrophomonas maltophilia strains.
  • Gene complementation assays to validate the role of specific genes (e.g., ompO) in stress tolerance.
  • Analysis of σ factor expression levels (rpoN, rpoP, rpoE) in response to OmpA mutation.
  • Construction and characterization of mutant strains for individual σ factors to assess their contribution to stress tolerance.

Main Results:

  • The ompO gene was significantly downregulated in the KJΔOmpA299-356 mutant, and its complementation restored menadione tolerance.
  • Expression of three σ factors, rpoN (downregulated), rpoP (upregulated), and rpoE (upregulated), was altered in the mutant.
  • Downregulation of rpoN and upregulation of rpoE were identified as key contributors to the decreased oxidative stress tolerance.
  • Loss of the OmpA C-terminal domain triggered an envelope stress response, leading to σE activation, which in turn reduced rpoN and ompO expression.

Conclusions:

  • The OmpA C-terminal domain is critical for maintaining oxidative stress tolerance in Stenotrophomonas maltophilia.
  • A regulatory circuit involving the ΔompA299-356 mutant, rpoE, and ompO mediates changes in oxidative stress tolerance.
  • Cross-regulation between rpoE and rpoN plays a significant role in the observed stress response phenotypes.
  • OmpA's interaction with the peptidoglycan layer is essential for envelope integrity and bacterial stress tolerance.