THE CYTOCHROME-C MATURATION OPERON IS INVOLVED IN MANGANESE OXIDATIONIN PSEUDOMONAS-PUTIDA GB-1

A Pseudomonas putida strain, strain GB-I, oxidizes Mn2+ to Mn ol;ide i n the early stationary growth phase. It also secretes a siderophore (i dentified as pyoverdine) when it is subjected to iron limitation, Afte r transposon (Tn5) mutagenesis several classes of mutants with differe nces in Mn2+ oxidation and/or secretion of the Mn2+-oxidizing activity were identified. Preliminary analysis of the Tn5 insertion site in on e of the nonoxidizing mutants suggested that a multicopper oxidase-rel ated enzyme is involved in Mn2+ oxidation. The insertion site in anoth er mutant was preliminarily identified as a gene involved in the gener al protein secretion pathway. Two mutants defective in Mn2+-oxidizing activity also secreted porphyrins into the medium and appeared to be d erepressed for pyoverdine production. These strains were chosen for de tailed analysis. Both mutants were shown to contain Tn5 insertions in the ccmF gene, which is part of the cytochrome c maturation operon. Th ey were cytochrome oxidase negative and did not contain c-type cytochr omes. Complementation with part of the ccm operon isolated from the wi ld type restored the phenotype of the parent strain, These results ind icate that a functional ccm operon is required for Mn2+ oxidation in P . putida GB-1, A possible relationship between porphyrin secretion res ulting from the ccm mutation and stimulation of pyoverdine production is discussed.