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The Neisseria gonorrhoeae photolyase orthologue phrB is required for proper DNA supercoiling but does not function in photo-reactivation.

ABSTRACT: Neisseria gonorrhoeae (Gc) is an obligate human pathogen and the causative agent of the sexually transmitted infection, gonorrhoea. Despite the fact that the gonococcus is not normally exposed to UV irradiation or visible light, the bacterium expresses a phrB orthologue, which in other organisms encodes a DNA photolyase that repairs UV-induced pyrimidine dimers with energy provided by visible light. We show that a Gc phrB mutant is not more sensitive to UV irradiation, independent of visible light exposure, and that the Gc phrB cannot complement an Escherichia coli phrB mutant strain. The Gc phrB mutant had a reduced colony size that was not a result of a growth defect and the mutant cells exhibited an altered morphology. Although the phrB mutant exhibited increased sensitivity to oxidative killing; it showed increased survival on media containing nalidixic acid or rifampicin, but did not have an increased mutation rate to these antibiotics or spectinomycin and kasugamycin. The Gc phrB mutant showed increased negative DNA supercoiling, but while the protein bound double-stranded DNA, it did not express topoisomerase activity. We conclude that the Gc PhrB has a previously unrecognized role in maintaining DNA supercoiling that is important for normal cell physiology.

SUBMITTER: Cahoon LA

PROVIDER: S-EPMC3079310 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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The Neisseria gonorrhoeae photolyase orthologue phrB is required for proper DNA supercoiling but does not function in photo-reactivation.

Cahoon Laty A LA Stohl Elizabeth A EA Seifert H Steven HS

Molecular microbiology 20101213 3

Neisseria gonorrhoeae (Gc) is an obligate human pathogen and the causative agent of the sexually transmitted infection, gonorrhoea. Despite the fact that the gonococcus is not normally exposed to UV irradiation or visible light, the bacterium expresses a phrB orthologue, which in other organisms encodes a DNA photolyase that repairs UV-induced pyrimidine dimers with energy provided by visible light. We show that a Gc phrB mutant is not more sensitive to UV irradiation, independent of visible lig ...[more]

PMID: 21255115

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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.

Dataset Information

The Neisseria gonorrhoeae photolyase orthologue phrB is required for proper DNA supercoiling but does not function in photo-reactivation.

Publications

The Neisseria gonorrhoeae photolyase orthologue phrB is required for proper DNA supercoiling but does not function in photo-reactivation.

Similar Datasets

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