Various mutants (lip) of Pseudomonas aeruginosa PA0 2302 that lacked extracellular lipase activity were isolated. They were selected on a calcium-triolein agar. The phenotypic characteristics of two of these mutants suggested that they were defective in the gene coding for lipase: both lip mutants produced no lipase in liquid-and on solid medium. They were nonpleiotropic with regard to various other exoproducts. None of the mutants released any putatively cell-bound lipase after treatment of

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... ls with Triton X-100 or alginate. The electrophoretic protein-and LPS-profiles of outer membranes derived from lip mutants and the parental strain were identical. The lip locus was mapped on the chromosome of P. aeruginosa PA0 1 by FP5-and R68.45-mediated crossings and by transduction with phage G 101. The lip locus was cotransduced with pyrF only (60%) indicating a map position at about 57 min. The lipase gene was cloned on a 3.1 kb SalI fragment using vector pKT248. The newly constructed plasmid was able to complement the lipase deficiency of the two lip mutants of P . aeruginosa.