The cytochromes c-550 of Paracoccus denitrificans and Thiosphaera pantotropha: A need for re-evaluation of the history of Paracoccus cultures

The c-type cytochrome and protein profiles were compared for a number of cultures of Paracoccus dentrificans obtained from a range of culture collections. The cultures fell into two groups corresponding to the two original isolates of this bacterial species. One group, which included NCIMB 8944, ATCC 13543, ATCC 17741, ATCC 19367, Pd 1222 and DSM 413, were similar or identical to LMD 22.21. The second group, including DSM 65 and LMG 4218, were similar or identical to LMD 52.44. These groupings were not compatible with the recorded history of culture deposition. Mass spectrometry and amino acid sequence comparisons showed that the cytochrome c-550 of the LMD 52.43 culture group differed by 16% from that of the LMD 22.21 group, and yet was only 1% different from the cytochrome c-550 of Thiosphaera pantotropha. These results suggest that consideration should be given to creation of a new species of Paracoccus pantotropha, which would include Thiosphaera pantotropha and Paracoccus denitrificans LMD 52.44.