Porphyromonas gingivalis (
P.g.) is a key pathogen involved in periodontal diseases. The aim of this study was to investigate the prevalence and phylogenetic origin of the lipoprotein-gene
ragB in its most virulent variant,
ragB-1 (co-transcribed with
ragA-1 as locus
rag-1),
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Porphyromonas gingivalis (
P.g.) is a key pathogen involved in periodontal diseases. The aim of this study was to investigate the prevalence and phylogenetic origin of the lipoprotein-gene
ragB in its most virulent variant,
ragB-1 (co-transcribed with
ragA-1 as locus
rag-1), in different
P.g. strains collected worldwide. A total of 138
P.g. strains were analyzed for the presence of
ragB-1 by pooled analysis and subsequently individual PCRs. Sequencing a core fragment of
ragB-1 of the individual strains made it possible to carry out a phylogenetic classification using sequence alignment. In total, 22 of the 138
P.g. strains tested positive for
ragB-1, corresponding to a prevalence of 16%. The fragment investigated was highly conserved, with variations in the base sequence detected in only three strains (OMI 1072, OMI 1081, and OMI 1074). In two strains, namely OMI 1072 (original name: I-433) and OMI 1081 (original name: I-372), which originate from monkeys, two amino-acid alterations were apparent. Since
ragB-1 has also been found in animal strains, it may be concluded that
rag-1 was transferred from animals to humans and that this originally virulent variant was weakened by mutations over time so that new, less virulent, adapted commensal versions of
rag (
rag-2,
-3,
and -4), with
P.g. as the host, evolved.
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