Homology with a repeated Yersinia pestis DNA sequence IS100 correlates with pesticin sensitivity in Yersinia pseudotuberculosis

Abstract

We have identified IS100 sequences in a specific subset of Yersinia pseudotuberculosis isolates that were also sensitive to the Y. pestis-produced bacteriocin, pesticin. In contrast, Y. pseudotuberculosis strains which did not contain IS100 sequences were not sensitive to pesticin. We propose that IS100 serves as a molecular marker that identifies a subset of Y. pseudotuberculosis isolates that have a particularly close evolutionary and/or ecological relationship with Y. pestis.Yersinia pestis, the causative agent of bubonic plague (1, 21), and Y. pseudotuberculosis are closely related at the genetic level, having more than 90% DNA homology overall (3,14,18). Despite this genetic similarity, these two species differ greatly in their means of transmission and disease presentation, indicating that important genotypic differences between the agents must also exist. Unlike plague, Y. pseudotuberculosis infection is rarely fatal and cannot be transmitted by fleas (32). Understanding the factors that differentiate Y. pestis from Y. pseudotuberculosis at the molecular and genetic levels may facilitate plague control efforts and provide insight into the evolution of pathogenic microorganisms.In previous studies, we identified two contiguous DNA fragments (probe fragments B and C) from the 9.5-kbp "pesticin plasmid," pKYP1, that hybridized with all Y. pestis isolates and a subset of Y. pseudotuberculosis strains that we tested (16). We were intrigued by the possibility that these DNA probes may identify a subset of Y. pseudotuberculosis isolates that are more closely related to Y. pestis than others and undertook a study to characterize further the nature of these cross-hybridizing DNA sequences. We now report that DNA probe fragments B and C encode IS100 and that the presence of this repeated sequence correlates with pesticin sensitivity in a clonal subset of Y. pseudotuberculosis isolates. In addition, we suggest that the distinctive and variable restriction fragment length polymorphism (RFLP) patterns observed with Y. pestis and Y. pseudotuberculosis make IS100 useful as a molecular epidemiological tool in investigating the spread of these organisms in the environment.Characterization of DNA probe fragment C. Initial experiments to define the boundaries and specificity of the crosshybridizing DNA sequences within fragment C were performed by colony blot hybridization analysis as described previously (16). Except as noted, Y. pestis and Y. pseudotuberculosis were collected during plague surveillance operations and were generously provided by T. Quan, Division of Viral and Vector-Borne Disease, Centers for Disease Control and Prevention (CDC), Fort Collins, Colo. All Y. pseudotuberculosis isolates were phenotypically Lcr ϩ when tested on magnesium-oxalate agar for calcium dependence (12,17). Yersinia species were grown at 28ЊC in brain heart infusion broth or on solid agar (Difco Laboratories, Detroit, Mich.). All of 27 Y. pestis and 12 (36%) of 33 Y. pseudotuberculosis isolates hybridized with the DNA probe fragment C....

Genome sequence of Yersinia pestis, the causative agent of plague

“…At least four different insertion sequences (IS) were found on the chromosome: 66 complete or partial copies of IS1541, 44 of IS100, 21 of IS285 and 9 of IS1661. Overall numbers of insertion sequence copies are around tenfold higher than in Y. pseudotuberculosis (IS1541, 7±13 copies 18 ; IS100, 0±6 copies 19 ). Fifty-eight pseudogenes were due to frameshift mutations (21 at homopolymeric tracts), 32 due to deletions, and the remainder due to in-frame stop codons.…”

Genome plasticity in Yersinia pestis The GenBank accession numbers for the sequences reported in this paper can be found in Table 1 T1 ; the GenBank accession number for DFR4 is AF426171.

“…It is becoming increasingly apparent that the acquisition of genes via lateral transfer is the basis of bacterial genome diversity (Ochman et al, 2000 ;Perna et al, 2001 (Achtman et al, 1999 ;McDonough & Hare, 1997 ;Lucier & Brubaker, 1992), as does the instability of the 102 kb pgm locus (Fetherston et al, 1992). The genome sequence of Y. pestis CO92 demonstrates the genetic flexibility of this strain (Parkhill et al, 2001).…”

“…They have been previously implicated in the strain variability of Y. pestis, namely by RFLP analysis of the IS100 location (Achtman et al, 1999 ;McDonough & Hare, 1997), and their presence contributes to the instability of the pgm locus (Buchrieser et al, 1998 ;Fetherston & Perry, 1994). In E. coli, the majority of insertion sequences are associated with lateral gene transfer, and they are frequently located at junctions of native and transferred DNA (Lawrence & Ochman, 1998).…”

“…These observations led to the proposal that Y. pestis is a recent, highly uniform clone of Y. pseudotuberculosis that arose between 1500 and 20 000 years ago (Achtman et al, 1999). Some genome plasticity was demonstrated by restriction fragment length polymorphism (RFLP) analysis of IS100 locations, enabling the construction of a phylogenetic tree in which the different biovars of Y. pestis are clustered together (Achtman et al, 1999 ;McDonough & Hare, 1997). Similarly, PFGE analysis of SpeI fragments of Y. pestis genomic DNA shows no variability within biovars, but some variation is seen between biovars (Lucier & Brubaker, 1992).…”

Current Trends in Plague Research: From Genomics to Virulence

“…19 Table 1 summarizes shared and unique properties of Y. pestis and Y. pseudotuberculosis that relate to virulence and physiologic differentiation. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]64 …”