Chromogenic method for rapid isolation of recA-like mutants of gram-negative bacteria.

We have devised a rapid and widely applicable color test for detecting recA-like mutants of gram-negative bacteria. The technique depends on decreased expression of an Escherichia coli recA-lacZ fusion in recA mutants and uses a broad-host-range plasmid to transfer the fusion gene into new species. We describe the isolation of a recA-like mutant of Pseudomonas syringae by this technique.