Prevalence, nucleotide sequence and expression studies of two proteins of a 5.6 kb, Class III, Bacteroides plasmid frequently found in clinical isolates from European countries

In order to gain information on the significance and functions of small molecular weight plasmids (usually regarded as cryptic) of Bacteroides isolates, we screened 178 European clinical Bacteroides isolates for plasmids and determined the nucleotide sequence of a 5.6 kb plasmid. The previously observed frequent plasmid types (Classes I–III; 2.7, 4.2 and 5.6 kb, respectively) were found to exhibit different distributions in five European countries as concerns plasmid type, geographical location, taxonomy and time course. The Class I plasmids displayed markedly different distribution properties from those of the Class II and III plasmids. The nucleotide sequence of a representative of the most frequent Class III plasmids, pBFP35, originating from Hungary, was determined (5594 bp) and analyzed. A total of eight open reading frames (ORFs) were annotated, of which four proved to participate unequivocally in such plasmid maintenance functions as replication (repAP35), mobilization (mobAP35) and stability (mazEP35 and mazFP35). Four additional ORFs (orf1–4) were identified. Orf1 was predicted to code a lipoprotein. In expression studies in an Escherichia coli host, Orf1 behaved as a periplasmic protein.