Cell to cell transmission of donor DNA overcomes differential incorporation of non-homologous and homologous markers in Neisseria gonorrhoeae.
The neisseriae are naturally competent for DNA transformation. This genetic study examines whether the modification status of chromosomal donor DNA affects transformation of Neisseria gonorrhoeae to drug resistance. When a single modification system was inactivated, unmodified chromosomal donor DNA was not restricted when used to transform the cognate restriction+ host, irrespective of whether the donor DNA carried a point mutation (homologous marker) or a drug-resistance gene cassette (non-homologous marker). These observations contrasted transformations performed with unmodified plasmid donor DNAs, where the incoming DNA was excluded. However, during the study, it became apparent that certain strains of gonococci showed differential incorporation of non-homologous markers when compared with the incorporation of the homologous marker, even when the donor DNAs were prepared from parental strains. Differential incorporation of markers could be rescued either through cell to cell transmission of donor DNA, or by performing in vitro transformations with donor DNA preparations that were obtained from spent culture supernatants. Overall, the data indicate that, in addition to the exclusion of foreign DNA through the requirement for a genus-specific uptake sequence, gonococci appear capable of excluding DNA on the basis of homology.
Hill
S A
SA
Department of Biological Sciences, Northern Illinois University, DeKalb, IL, USA. sahill@niu.edu
D003227:Conjugation, Genetic; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics*; D015257:DNA-Cytosine Methylases / Q000235:genetics / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics*; D009344:Neisseria gonorrhoeae / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D010641:Phenotype; D011995:Recombination, Genetic; D014170:Transformation, Genetic
D015280:DNA Restriction-Modification Enzymes; D004269:DNA, Bacterial; D005819:Genetic Markers; D015257:DNA-Cytosine Methylases; C027823:Cytosine 5-methyltransferase