Sammendrag
The pathogenic Neisseria species, N. meningitidis and N. gonorrhoeae are readily transformed in vitro by exogenous heterologous DNA, such as antibiotic resistance cassettes. The closely related and generally harmless commensal species N. lactamica (Nla) is less tolerant of DNA heterology and has previously not been described to be competent for natural transformation. A possible explanation for this observation is that Nla-specific restriction endonucleases limit the transformability of Nla. Here, we provide evidence to support this hypothesis, including bioinformatics data consistent with the presence of an abundance of restriction-modification (RM) systems in Nla. Bioinformatics studies also demonstrated an aberrantly low frequency of the restriction/modification site CATG in the Nla genome, which can be attributed to restriction site avoidance. Furthermore, inactivation of genes encoding selected endonucleases increased the efficiency of Nla transformation with heterologous DNA. These results suggest that engineered Nla strains in which one or more RM systems are inactivated could be useful tools for developing anti-microbial vaccines.
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