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Neisseria gonorrhoeae and humans perform an evolutionary LINE dance.

ABSTRACT: Horizontal gene transfer is an important mechanism for generating genetic diversity. As the number of sequenced genomes continues to increase, so do the examples of horizontal genetic exchange between both related and divergent organisms. Here we discuss the recent finding that certain strains of the human pathogen Neisseria gonorrhoeae have incorporated a small fragment of human DNA sequence into their genomes. The horizontally acquired sequence exhibits 98-100% nucleotide identity to a 685 bp portion of the highly repetitive retrotransposable element L1 and its presence in the gonococcal genome has been confirmed by multiple molecular techniques. The possibility of similar L1 horizontal gene transfer events having occurred in other bacteria based on genomic sequence evidence is explored. Potential mechanisms of how N. gonorrhoeae was able to acquire and maintain this human sequence are also discussed in addition to the evolutionary implications of such an event.

SUBMITTER: Anderson MT

PROVIDER: S-EPMC3190277 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Neisseria gonorrhoeae and humans perform an evolutionary LINE dance.

Anderson Mark T MT Seifert H Steven HS

Mobile genetic elements 20110501 1

Horizontal gene transfer is an important mechanism for generating genetic diversity. As the number of sequenced genomes continues to increase, so do the examples of horizontal genetic exchange between both related and divergent organisms. Here we discuss the recent finding that certain strains of the human pathogen Neisseria gonorrhoeae have incorporated a small fragment of human DNA sequence into their genomes. The horizontally acquired sequence exhibits 98-100% nucleotide identity to a 685 bp ...[more]

PMID: 22016852

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Project description:BackgroundVarious typing methods have been developed for Neisseria gonorrhoeae, but none provide the combination of discrimination, reproducibility, portability, and genetic inference that allows the analysis of all aspects of the epidemiology of this pathogen from a single data set. Multilocus sequence typing (MLST) has been used successfully to characterize the related organisms Neisseria meningitidis and Neisseria lactamica. Here, the same seven locus Neisseria scheme was used to characterize a diverse collection of N. gonorrhoeae isolates to investigate whether this method would allow differentiation among isolates, and to distinguish these three species.ResultsA total of 149 gonococcal isolates were typed and submitted to the Neisseria MLST database. Although relatively few (27) polymorphisms were detected among the seven MLST loci, a total of 66 unique allele combinations (sequence types, STs), were observed, a number comparable to that seen among isolate collections of the more diverse meningococcus. Patterns of genetic variation were consistent with high levels of recombination generating this diversity. There was no evidence for geographical structuring among the isolates examined, with isolates collected in Liverpool, UK, showing levels of diversity similar to a global collection of isolates. There was, however, evidence that populations of N. meningitidis, N. gonorrhoeae and N. lactamica were distinct, with little support for frequent genetic recombination among these species, with the sequences from the gdh locus alone grouping the species into distinct clusters.ConclusionThe seven loci Neisseria MLST scheme was readily adapted to N. gonorrhoeae isolates, providing a highly discriminatory typing method. In addition, these data permitted phylogenetic and population genetic inferences to be made, including direct comparisons with N. meningitidis and N. lactamica. Examination of these data demonstrated that alleles were rarely shared among the three species. Analysis of variation at a single locus, gdh, provided a rapid means of identifying misclassified isolates and determining whether mixed cultures were present.

Project description:Many clinical isolates of the human pathogen Neisseria gonorrhoeae contain conjugative plasmids. The host range of these plasmids is limited to Neisseria species, but presence of a tetracycline (tetM) determinant inserted in several of these plasmids is an important cause of the rapid spread of tetracycline resistance. Previously plasmids with different backbones (Dutch and American type backbones) and with and without different tetM determinants (Dutch and American type tetM determinants) have been identified. Within the isolates tested, all plasmids with American or Dutch type tetM determinants contained a Dutch type plasmid backbone. This demonstrated that tetM determinants should not be used to differentiate between conjugal plasmid backbones. The nucleotide sequences of conjugative plasmids with Dutch type plasmid backbones either not containing the tetM determinant (pEP5233) or containing Dutch (pEP5289) or American (pEP5050) type tetM determinants were determined. Analysis of the backbone sequences showed that they belong to a novel IncP1 subfamily divergent from the IncP1alpha, beta, gamma, delta and epsilon subfamilies. The tetM determinants were inserted in a genetic load region found in all these plasmids. Insertion was accompanied by the insertion of a gene with an unknown function, and rearrangement of a toxin/antitoxin gene cluster. The genetic load region contains two toxin/antitoxins of the Zeta/Epsilon toxin/antitoxin family previously only found in Gram positive organisms and the virulence associated protein D of the VapD/VapX toxin/antitoxin family. Remarkably, presence of VapX of pJD1, a small cryptic neisserial plasmid, in the acceptor strain strongly increased the conjugation efficiency, suggesting that it functions as an antitoxin for the conjugative plasmid. The presence of the toxin and antitoxin on different plasmids might explain why the host range of this IncP1 plasmid is limited to Neisseria species. The isolated plasmids conjugated efficiently between N. gonorrhoeae strains, but did not enhance transfer of a genetic marker.

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Neisseria gonorrhoeae and humans perform an evolutionary LINE dance.

Publications

Neisseria gonorrhoeae and humans perform an evolutionary LINE dance.

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