Dataset Information

Simultaneous Presence of Insertion Sequence Excision Enhancer and Insertion Sequence IS629 Correlates with Increased Diversity and Virulence in Shiga Toxin-Producing Escherichia coli.

ABSTRACT: Although new serotypes of enterohemorrhagic Escherichia coli (EHEC) emerge constantly, the mechanisms by which these new pathogens arise and the reasons emerging serotypes tend to carry more virulence genes than other E. coli are not understood. An insertion sequence (IS) excision enhancer (IEE) was discovered in EHEC O157:H7 that promoted the excision of IS3 family members and generating various genomic deletions. One IS3 family member, IS629, actively transposes and proliferates in EHEC O157:H7 and enterotoxigenic E. coli (ETEC) O139 and O149. The simultaneous presence of the IEE and IS629 (and other IS3 family members) may be part of a system promoting not only adaptation and genome diversification in E. coli O157:H7 but also contributing to the development of pathogenicity among predominant serotypes. Prevalence comparisons of these elements in 461 strains, representing 72 different serotypes and 5 preassigned seropathotypes (SPT) A to E, showed that the presence of these two elements simultaneously was serotype specific and associated with highly pathogenic serotypes (O157 and top non-O157 Shiga toxin-producing Escherichia coli [STEC]) implicated in outbreaks and sporadic cases of human illness (SPT A and B). Serotypes lacking one or both elements were less likely to have been isolated from clinical cases. Our comparisons of IEE sequences showed sequence variations that could be divided into at least three clusters. Interestingly, the IEE sequences from O157 and the top 10 non-O157 STEC serotypes fell into clusters I and II, while less commonly isolated serotypes O5 and O174 fell into cluster III. These results suggest that IS629 and IEE elements may be acting synergistically to promote genome plasticity and genetic diversity among STEC strains, enhancing their abilities to adapt to hostile environments and rapidly take up virulence factors.

SUBMITTER: Toro M

PROVIDER: S-EPMC4609730 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Simultaneous Presence of Insertion Sequence Excision Enhancer and Insertion Sequence IS629 Correlates with Increased Diversity and Virulence in Shiga Toxin-Producing Escherichia coli.

Toro M M Rump L V LV Cao G G Meng J J Brown E W EW Gonzalez-Escalona N N

Journal of clinical microbiology 20150819 11

Although new serotypes of enterohemorrhagic Escherichia coli (EHEC) emerge constantly, the mechanisms by which these new pathogens arise and the reasons emerging serotypes tend to carry more virulence genes than other E. coli are not understood. An insertion sequence (IS) excision enhancer (IEE) was discovered in EHEC O157:H7 that promoted the excision of IS3 family members and generating various genomic deletions. One IS3 family member, IS629, actively transposes and proliferates in EHEC O157:H ...[more]

PMID: 26292302

Similar Datasets

Project description:Lactose utilization is one of the general biochemical characteristics of Escherichia coli, and the lac operon is responsible for this phenotype, which can be detected on lactose-containing media, such as MacConkey agar, after 24 h of incubation. However, some Shiga toxin-producing E. coli (STEC) O121:H19 strains exhibit an unusual phenotype called delayed lactose utilization (DLU), in which lactose utilization can be detected after 48 h of cultivation but not after only 24 h of cultivation. Insertion of an insertion sequence (IS), IS600, into the lacZ gene appears to be responsible for the DLU phenotype, and exposure to lactose has been reported to be necessary to observe this phenotype, but the mechanism underlying these phenomena remains to be elucidated. Here, we performed detailed analyses of the lactose utilization abilities of a set of O121:H19 strains and their mutants and found that IS-excision enhancer (IEE)-mediated excision of IS600 reactivates the lacZ gene and that the selective proliferation of IS-cured subclones in lactose-supplemented culture medium is responsible for the expression of the DLU phenotype. In addition, we analyzed the patterns of IS insertion into the lacZ and iee genes in the global O121:H19 population and revealed that while there are O121:H19 strains or lineage/sublineages that contain the IS insertion into iee or intact lacZ and thus do not show the DLU phenotype, most currently circulating O121:H19 strains contain IS600-inserted lacZ and intact iee and thus exhibit this phenotype. IMPORTANCE Insertion sequences (ISs) can modulate gene expression by gene inactivation or activation. While phenotypic changes due to IS insertion/transposition are frequently observed, gene reactivation by precise or simple IS excision rarely occurs. In this study, we show that IS600 is excised from the lacZ gene by IS-excision enhancer (IEE) during the cultivation of Shiga toxin-producing Escherichia coli (STEC) O121:H19 strains that show an unusual phenotype called delayed lactose utilization (DLU). This excision rescued their lactose utilization defect, and the subsequent selective proliferation of IS-cured subclones in lactose-containing medium resulted in the expression of the DLU phenotype. As we also show that most currently circulating O121:H19 strains exhibit this phenotype, this study not only provides information helpful for the isolation and identification of O121:H19 STEC but also offers novel insights into the roles of IS and IEE in the generation of phenotypic variation in bacterial populations.

Dataset Information

Simultaneous Presence of Insertion Sequence Excision Enhancer and Insertion Sequence IS629 Correlates with Increased Diversity and Virulence in Shiga Toxin-Producing Escherichia coli.

Publications

Simultaneous Presence of Insertion Sequence Excision Enhancer and Insertion Sequence IS629 Correlates with Increased Diversity and Virulence in Shiga Toxin-Producing Escherichia coli.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets