Homology among extra-cryptic DNA bands and the typical plasmids in Brazilian Yersinia pestis strains

Abstract

Yersinia pestis, the etiologic agent of plague, harbors three well-characterized plasmids: pFra (90-110kb), pYV (70 kb) and pPst (9.5 kb). Furthermore, some extra-cryptic DNA bands have been observed in a number of wild strains from several foci of the world. Additional bands have also been reported in Brazilian strains. Looking for any relationship among these cryptic DNA bands and the three-prototypical plasmids, we analyzed twelve strains displaying different plasmid content. The DNA bands were hybridized by southern blot with probes directed at the genes caf1, lcrV and pla located respectively on the plasmids pFra, pYV and pPst. The probes were constructed by PCR amplification and labeled with digoxigenin. The Pla probe hybridized with its target (pPst) and with bands of about 35 kb suggesting some homology among them. The Caf1 probe hybridized with the target (pFra) as well as with higher bands. The LcrV also hybridized with the target (pYV) and both with the bands higher than pFra and the bands between pFra and pYV. These results suggest that the large-cryptic bands could represent some rearrangement, open circular or linearized forms of the pFra and pYV plasmids.

Subtyping Brazilian Yersinia pestis strains by pulsed-field gel electrophoresis

“…Leal-Balbino et al (2004 and Leal et al (2000) observed spontaneous alterations in the genome (plasmid and chromosomal) of Brazilian Y. pestis as a result of prolonged storage and handling in the laboratory. The stability of the PFGE profiles was investigated by the analysis of serial subcultures of three strains.…”

“…Pigmentation segment deletion and plasmid deletions in Brazilian strains have been reported (Almeida et al, 1994;Leal et al, 2000;Leal-Balbino et al, 2006). Moreover, Guiyoule et al (1994) found a pigmentation deletion in vitro, which gave a new PFGE type, although they did not suggest that all new PFGE types were due to this deletion.…”

“…These cultures are deposited in the Yersinia spp Collection (Fiocruz -CYP) maintained by the National Service for Reference in Plague from the Centro de Pesquisas Aggeu Magalhães, FIOCRUZ-PE (SRP/FIOCRUZ-PE), Recife, PE, Brazil (Rocha et al, 2009). The strains appeared to be homogenous regardless of their origin concerning their plasmid content (Leal et al, , 2000, outer membrane protein profile (Abath et al, 1989), and RAPD and PCR -ribotyping analysis (Leal NC and Sobreira MBS, unpublished results). Currently, studies on the molecular epidemiology of Y. pestis have been hampered due to the great similarity of isolates (Vogler et al, 2011).…”

Genetic diversity of Yersinia pestis in Brazil

“…Alternatively, the strains could be inaccurate representatives of the original isolates, and these differences could be due to handling procedures during the prolonged storage of the strains in the laboratory since their isolation (Revazishvili et al, 2008;Vogler et al, 2011). Leal et al (2000) and Leal-Balbino et al (2004, 2006 observed spontaneous changes in the genome (both plasmid and chromosomal) of Brazilian Y. pestis following prolonged storage and laboratory handling. However, analysis of the 12 VNTR loci in the three parental strains and their derived cultures did not reveal changes in the studied regions, confirming their stability as previously observed (Adair et al, 2000;Keim et al, 2000).…”

Transmission of Yersinia pestis cultures with different plasmid content from Xenopsylla cheopis to Calomys callosus

“…pestis strains lacking plasmids or carrying additional cryptic plasmids have also been found in nature (Filippov et al 1990;Balakhonov et al 1991). In a later study, Leal et al (2000) showed that a 30 kb atypical DNA band is probably a larger form of pPst and that a >90 kb DNA band could comprise open circular or linearized form of the pFra and pYV plasmids. In a later study, Leal et al (2000) showed that a 30 kb atypical DNA band is probably a larger form of pPst and that a >90 kb DNA band could comprise open circular or linearized form of the pFra and pYV plasmids.…”