Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that can cause both acute and chronic infections in immunocompromised patients through wound, urethra, respiratory tract and cornea. P. aeruginosa can secrete several virulence factors such as the well-known elastase B that plays an important role in bacterial infection. However, the proteolytic processing of the secretome of P. aeruginosa remains largely unknown. In this study, we examined several physiology and pathogenesis proportion of P. aeruginosa B136-33, ΔpaaP, ΔlasA, ΔlasB and ΔprpL, such as growth rate, ability of substrate degradation, stimulation of the immune response, and bacterial adhesion to and penetration into epithelial cells. We also determined the secretome of P. aeruginosa wild type strain and protease mutant strains to understand how PaaP, LasA, LasB and PrpL modulate extracellular proteins. The result showed that ΔlasB and ΔprpL grew at a slower rate in low nutrition medium. The protease mutant ΔlasB displayed a decreased ability of biofilm formation and degradation of several substrates (eg, laminin, entactin, alpha-2-macroglobulin and Transferrin). Bacterial adhesion to and penetration into Int 407 cell were significantly decreased in ΔpaaP, ΔlasA, ΔlasB, and ΔprpL. In the aspect of immune response, macrophage secreted higher concentration of IL-6 after ΔlasB supernatant stimulated, and lower concentration of IL-6 after ΔprpL supernatant stimulated. According to the result of secretome analysis, protease mutant strain ΔpaaP, ΔlasA, ΔlasB, and ΔprpL displayed 3, 37, 60 and 38 secreted proteins, which were different from that of the wild type strain, respectively. The proteins associated with bacterial growth and regulating host immune proteins were significantly decreased in four mutant strains, such as immunomodulatory metalloproteinases, peptidases and enzymes involved in energy synthesis. Taken together, P. aeruginosa proteases are not only important role of virulence factors, but important role in proteolytic processing of the secretome and modulating host proteins. These findings can lead to comprehensive understanding of the role of P. aeruginosa proteases and providing information for searching targets to reduce P. aeruginosa infection.