Limited variation and maintenance of tight genetic linkage characterize heteroallelic pilE recombination following DNA transformation of Neisseria gonorrhoeae.
Genetic recombination impacts on neisserial biology in two ways: (i) specific loci undergo rearrangement at high frequency leading to the formation of many different alleles; and (ii) Neisseria, being naturally competent for DNA transformation, provide a means to disseminate the novel alleles throughout a population. In this study pilE was used as a model system to examine heteroallelic recombination following DNA transformation. When gonococci were transformed with chromosomal donor DNA containing different pilE alleles, the majority of pilE recombinants arose through allelic replacement. Co-conversion analysis across pilE showed that in approximately 85-90% of recombination events encompassing pilE and an adjacent opa locus, linkage was maintained (i.e. approximately 10-15% of recombination events terminated within the approximately 1000 base pair pilE/opaE interval). In addition to those recombinants that arose through allelic replacement, a large pilus-minus subpopulation was also observed (approximately 10% of all recombinants), indicating that many recombination events did not yield recombinant pilEs that could be assembled into functional pili. PilE mosaics increased following transformation with plasmid donor DNAs carrying pilE with limited flanking-sequence homology, suggesting a potential role for flanking-sequence homologies in mosaic formation. Overall, the data support the view that horizontal transmission of chromosomal DNA between gonococci will favour the spread of intact alleles, as opposed to expanding the allelic repertoire through the formation of gene mosaics.
Hill
S A
SA
Laboratory of Microbial Structure and Function, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics*; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004269:DNA, Bacterial; D036781:Fimbriae Proteins; D008040:Genetic Linkage; D005819:Genetic Markers; D014644:Genetic Variation; D008562:Membrane Glycoproteins / Q000235:genetics*; D009344:Neisseria gonorrhoeae / Q000235:genetics*; D018933:Pili, Sex / Q000235:genetics; D010957:Plasmids; D011995:Recombination, Genetic; D014169:Transformation, Bacterial
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005819:Genetic Markers; D008562:Membrane Glycoproteins; C074063:pilE protein, Neisseria gonorrhoeae; D036781:Fimbriae Proteins; D015500:Chloramphenicol O-Acetyltransferase