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The cytoplasmic membrane protein CcmC is, together with other Ccm proteins, a component for the maturation of c-type cytochromes in Gram-negative bacteria. A Pseudomonas fluorescens ATCC 17400 ccmC mutant is cytochrome c-deficient and shows considerably reduced production of the two siderophores pyoverdine and quinolobactin, paralleled by a general inability to utilize various iron sources, with the exception of haem. The ccmC mutant accumulates in a 5-aminolevulinic acid-dependent synthesis a reddish, fluorescent pigment identified as protoporphyrin IX. As a consequence a visA phenotype similar to that of a ferrochelatase-deficient hemH mutant characterized by drastically reduced growth upon light exposure was observed for the ccmC mutant. The defect of iron-protoporphyrin formation was further demonstrated by the failure of ccmC cell-free proteinase K-treated extracts to stimulate the growth of a haem auxotrophic hemH indicator strain, compared to similarly prepared wild-type extracts. In addition, the ccmC mutant did not sustain hemH growth in cross-feeding experiments while the wild-type did. Significantly reduced resistance to oxidative stress mediated by haem-containing catalases was observed for the ccmC mutant. A double hemH ccmC mutant could not be obtained in the presence of external haem without the hemH gene in trans, indicating that the combination of the two mutations is lethal. It was concluded that CcmC, apart from its known function in cytochrome c biogenesis, plays a role in haem biosynthesis. A function in the regulatory co-ordination of iron acquisition via siderophores, iron insertion into porphyrin via ferrochelatase and iron--protoporphyrin export for cytochrome c formation is predicted.

The haem pigment of Porphyromonas gingivalis is composed of [micro]-oxo bishaem, [[Fe(III)PPIX].sub.2]O, but the nature of that generated by Prevotella species has not been established. Mossbauer, Raman and UV-visible spectrophotometry were used to characterize the haem pigment of Prevotella intermedia and Prevotella nigrescens. M6ssbauer and Raman spectroscopy revealed the major haem species to be monomeric iron protoporphyrin IX, Fe(III)PPIX.OH (haematin). The terminal growth pH of both species on blood agar was between 5.8 and 6.0, which favours the formation and maintenance of monomeric Fe(III)PPIX.OH. Incubation of Pr. nigrescens and Pr. intermedia with oxyhaemoglobin at pH 6.5 resulted in formation of aquomethaemoglobin which was degraded to generate Fe(III) PPIX.OH which in turn became cell-associated, whilst incubation at pH 7*5 resulted in formation of [[Fe(III)PPIX].sub.2]O. It is concluded that both Prevotella species degrade oxyhaemoglobin to form [[Fe(III)PPIX].sub.2]O as an intermediate, which is converted to Fe(III)PPIX.OH through a depression in pH. The low pH encourages cell-surface deposition of insoluble Fe(III)PPIX.OH which would act as a barrier against oxygen and reactive oxygen species, and also protect against [H.sub.2][O.sub.2] through its inherent catalase activity.

Research has been conducted on Burkholderia cepacia which isolates genomovar III. Results demonstrate that B. cepacia genomovar IIIa strains express outer-membrane proteins which bind and convert monomers into mu-oxo oligomeric form.