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Open Access Research article

Expression of mucoid induction factor MucE is dependent upon the alternate sigma factor AlgU in Pseudomonas aeruginosa

Yeshi Yin13, F Heath Damron17, T Ryan Withers1, Christopher L Pritchett56, Xin Wang3, Michael J Schurr5 and Hongwei D Yu124*

Author Affiliations

1 Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine at Marshall University, Huntington, WV 25755, USA

2 Department of Pediatrics, Joan C. Edwards School of Medicine at Marshall University, Huntington, WV 25755, USA

3 Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, No. 198, Shiqiao Road, Hangzhou 310021, China

4 Progenesis Technologies, LLC, 1111 Veterans Memorial Blvd, Huntington, WV 25701, USA

5 Department of Microbiology, School of Medicine, University of Colorado, Aurora, Colorado 80045, USA

6 Department of Health Sciences, East Tennessee State University, Johnson City, TN 37615, USA

7 Division of Infectious Diseases and International Health, University of Virginia, Box 800419, MR-6, Charlottesville, VA 22908, USA

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BMC Microbiology 2013, 13:232  doi:10.1186/1471-2180-13-232

Published: 18 October 2013

Abstract

Background

Alginate overproduction in P. aeruginosa, also referred to as mucoidy, is a poor prognostic marker for patients with cystic fibrosis (CF). We previously reported the construction of a unique mucoid strain which overexpresses a small envelope protein MucE leading to activation of the protease AlgW. AlgW then degrades the anti-sigma factor MucA thus releasing the alternative sigma factor AlgU/T (σ22) to initiate transcription of the alginate biosynthetic operon.

Results

In the current study, we mapped the mucE transcriptional start site, and determined that PmucE activity was dependent on AlgU. Additionally, the presence of triclosan and sodium dodecyl sulfate was shown to cause an increase in PmucE activity. It was observed that mucE-mediated mucoidy in CF isolates was dependent on both the size of MucA and the genotype of algU. We also performed shotgun proteomic analysis with cell lysates from the strains PAO1, VE2 (PAO1 with constitutive expression of mucE) and VE2ΔalgU (VE2 with in-frame deletion of algU). As a result, we identified nine algU-dependent and two algU-independent proteins that were affected by overexpression of MucE.

Conclusions

Our data indicates there is a positive feedback regulation between MucE and AlgU. Furthermore, it seems likely that MucE may be part of the signal transduction system that senses certain types of cell wall stress to P. aeruginosa.

Keywords:
Pseudomonas aeruginosa; Alginate; Mucoidy; AlgU/T; MucE; Sigma factor