The type II secretion system (Xcp) of Pseudomonas putida is active and involved in the secretion of phosphatases

• Published in: Environmental microbiology Vol. 15; no. 10; pp. 2658 - 2671
• Main Authors: Putker, Florian, Tommassen-van Boxtel, Ria, Stork, Michiel, Rodríguez-Herva, José J., Koster, Margot, Tommassen, Jan
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.10.2013; Blackwell; Wiley Subscription Services, Inc
• Subjects: Animal, plant and microbial ecology; Bacterial Secretion Systems - genetics; Bacteriology; Biological and medical sciences; Cell Membrane - genetics; Cell Membrane - secretion; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; General aspects; Genes, Bacterial - genetics; Genomes; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Microbial ecology; Microbiology; Miscellaneous; Phosphates - metabolism; Phosphoric Monoester Hydrolases - genetics; Phosphoric Monoester Hydrolases - secretion; Protein Transport; Pseudomonas aeruginosa - genetics; Pseudomonas aeruginosa - metabolism; Pseudomonas putida; Pseudomonas putida - enzymology; Pseudomonas putida - genetics; Pseudomonadales; Bacteria; Pseudomonadaceae; Type II secretion system; Secretion; Pseudomonas putida
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.12115

Summary The genome of the Gram‐negative bacterium Pseudomonas putida harbours a complete set of xcp genes for a type II protein secretion system (T2SS). This study shows that expression of these genes is induced under inorganic phosphate (Pi) limitation and that the system enables the utilization of various organic phosphate sources. A phosphatase of the PhoX family, previously designated UxpB, was identified, which was produced under low Pi conditions and transported across the cell envelope in an Xcp‐dependent manner demonstrating that the xcp genes encode an active T2SS. The signal sequence of UxpB contains a twin‐arginine translocation (Tat) motif as well as a lipobox, and both processing by leader peptidase II and Tat dependency were experimentally confirmed. Two different tat gene clusters were detected in the P. putida genome, of which one, named tat‐1, is located adjacent to the uxpB and xcp genes. Both Tat systems appeared to be capable of transporting the UxpB protein. However, expression of the tat‐1 genes was strongly induced by low Pi levels, indicating a function of this system in survival during Pi starvation.