Molecular organization of the xcp gene cluster in Pseudomonas putida:: absence of an xcpX (gspK) homologue

A DNA fragment containing rep (gsp) gene homologues, required for extracellular protein secretion by the general secretory pathway (GSP) in Various Gram-negative bacteria, was cloned from Pseudomonas putida (Pp) strain WCS358 and sequenced. The results presented here and those previously reported (de Groot, A., Krijger, J.-J., Filloux, A., Tommassen, J., 1996). Characterization of type II protein secretion (xcp) genes in the plant growth-stimulating Pseudomonas putida, strain WCS358 Mel. Gen. Genet. 250, 491-504) complete the sequence of the rep gene cluster of Pp. Unlike that of Pseudomonas aeruginosa (Pa), the rep gene cluster of Pp contains a gspN homologue. More surprisingly, in contrast to all known gsp gene clusters, the xcpX (gspK) homologue is not found. In addition, genes flanking the rep cluster of Pp are not related to those flanking the rep genes of Pa. Overall, the rep gene products of Pp are as much related to those of Pa as to gsp gene products of enterobacterial species, suggesting that the rep clusters of Pp and Pa have evolved separately. (C) 1999 Elsevier Science B.V. All rights reserved.