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CRISPR1 analysis of naturalized surface water and fecal Escherichia coli suggests common origin.

ABSTRACT: Clustered regularly interspaced short palindromic repeats (CRISPRs) are part of an acquired bacterial immune system that functions as a barrier to exogenous genetic elements. Since naturalized Escherichia coli are likely to encounter different genetic elements in aquatic environments compared to enteric strains, we hypothesized that such differences would be reflected within the hypervariable CRISPR alleles of these two populations. Comparison of CRISPR1 alleles from naturalized and fecal phylogroup B1 E. coli strains revealed that the alleles could be categorized into four major distinct groups (designated G6-G9), and all four allele groups were found among naturalized strains and fecal strains. The distribution of CRIPSR G6 and G8 alleles was similar among strains of both ecotypes, while naturalized strains tended to have CRISPR G7 alleles rather than G9 alleles. Since CRISPR G7 alleles were not specific to naturalized strains, they, however, would not be useful as a marker for identifying naturalized strains. Notably, CRISPR alleles from naturalized and fecal strains also had similar spacer repertoires. This indicates a shared history of encounter with mobile genetic elements and suggests that the two populations were derived from common ancestors.

SUBMITTER: Tymensen LD

PROVIDER: S-EPMC4906003 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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CRISPR1 analysis of naturalized surface water and fecal Escherichia coli suggests common origin.

Tymensen Lisa D LD

MicrobiologyOpen 20160322 3

Clustered regularly interspaced short palindromic repeats (CRISPRs) are part of an acquired bacterial immune system that functions as a barrier to exogenous genetic elements. Since naturalized Escherichia coli are likely to encounter different genetic elements in aquatic environments compared to enteric strains, we hypothesized that such differences would be reflected within the hypervariable CRISPR alleles of these two populations. Comparison of CRISPR1 alleles from naturalized and fecal phylog ...[more]

PMID: 27004771

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Project description:The model prokaryote Escherichia coli can exist as a either a commensal or a pathogen in the gut of diverse mammalian hosts. These associations, coupled with its ease of cultivation and genetic variability, have made E. coli a popular indicator organism for tracking the origin of fecal water contamination. Source tracking accuracy is predicated on the assumption that E. coli isolates recovered from contaminated water present a genetic signature characteristic of the host from which they originated. In this study, we compared the accuracy with which E. coli isolated from humans, bear, cattle and deer could be identified by standard fingerprinting methods used for library-based microbial source tracking (repetitive element PCR and pulsed-field gel electrophoresis) in relation to microarray-based analysis of genome content. Our results show that patterns of gene presence or absence were more useful for distinguishing E. coli isolates from different sources than traditional fingerprinting methods, particularly in the case of human strains. Host-associated differences in genome composition included the presence or absence of mobile IS1 elements as well as genes encoding the ferric dicitrate iron transporter (fec), E. coli common pilus (ECP), type 1 fimbriae and the CRISPR associated cas proteins. Many of these differences occurred in regions of the E. coli chromosome previously shown to be M-bM-^@M-^\hot spotsM-bM-^@M-^] for the integration of horizontally-acquired DNA. PCR primers designed to amplify the IS1 and fec loci confirmed array results and demonstrated the ease with which gene presence/absence data can be converted into a diagnostic assay. The data presented here suggest that, despite the high level of genetic diversity observed among isolates by PFGE, human-derived strains may constitute a distinct ecotype distinguished by multiple potential library-independent source tracking markers. Twelve isolates of E. coli ( 3 from bear, 3 from cattle, 3 from deer and 3 from humans) were isolated from feces and/or raw sewage. Genome content for each strain was assessed in duplicate using comparative genome hybridization with E. coli K12 MG1655 as the reference for a total of 24 arrays.

Dataset Information

CRISPR1 analysis of naturalized surface water and fecal Escherichia coli suggests common origin.

Publications

CRISPR1 analysis of naturalized surface water and fecal Escherichia coli suggests common origin.

Similar Datasets

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