HEME-O AND HEME-A PUTATIVE CYTOCHROME BO IN A MUTANT OF BACILLUS-CEREUS IMPAIRED IN THE SYNTHESIS OF HEME-A

In a spontaneous mutant (PYM1) of Bacillus cel eus impaired in the syn thesis of haem Al no haem-A-containing cytochromes were detected spect roscopically. The haem A deficiency was compensated by high levels of haem O and a GO-reactive cytochrome o in membranes; no other oxidases were detected. In contrast, the wild-type strain had considerable amou nts of haem A and negligible levels of haem O. The mutant PYM1 exhibit ed normal colony morphology. growth, and sporulation in nonfermentable media, whereas on fermentable media, the mutant overproduced acid, wh ich led to poor growth and inhibition of sporulation. External control of the pH of the medium in fermentable media allowed close-to-normal growth and massive sporulation of the mutant. The presence of membrane -bound cytochrome caa(3)-OII and aa(3)-II subunits in strain PYM1 was confirmed by Western blots and haem C staining (COLI subunit). Western blotting also revealed that in contrast to the wild-type - strain PYM 1 contained the membrane-bound subunits caa(3)-COI and aa(3)-I, but in low amounts. The effect of several respiratory inhibitors on the resp iratory system of strain PYM1 suggested that the terminal oxidase is h ighly resistant to KCN and CO and that a c-type cytochrome might be in volved in the electron transfer sequence to the putative cytochrome bo .