Staphylococcus aureus nuclease is a useful secretion reporter for mycobacteria

A secretion reporter system based on Staphylococcus aureus nuclease (nuc) w as developed for use in mycobacteria. Fusion of secretion signals to the re porter cloned in a shuttle vector, pBPnuc1, resulted in halo formation arou nd colonies of Mycobacterium smegmatis and Mycobacterium tuberculosis grown on DNase agar plates containing Methyl Green indicator dye. This in-situ d etection system was used to identify secreted proteins by screening a pBPnu c1::H37Rv nuc gene fusion library in M. smegmatis. The clones identified in this screen all formed colony halos when present in M. tuberculosis grown on indicator media. The proteins corresponded to DesA2, a stearoyl-acyl car rier protein desaturase, PepA, a putative serine protease and the Apa antig en, which is the ATP-binding subunit of an ABC transport system. Of these p roteins, only PepA and Apa contained recognizable leader peptides. (C) 1999 Elsevier Science B.V. All rights reserved.