DNA Uptake Sequence-Mediated Enhancement of Transformation in Neisseria gonorrhoeae Is Strain Dependent

Abstract

ABSTRACT Natural transformation is the main means of horizontal genetic exchange in the obligate human pathogen Neisseria gonorrhoeae. Neisseria spp. have been shown to preferentially take up and transform their own DNA by recognizing the nonpalindromic 10- or 12-nucleotide sequence 5′- AT GCCGTCTGAA-3′ (additional semiconserved nucleotides are underlined), termed the DNA uptake sequence (DUS10 or DUS12). Here we investigated the effects of the DUS on transformation and DNA uptake for several laboratory strains of N. gonorrhoeae . We found that all strains showed efficient transformation of DUS containing DNA (DUS10 and DUS12) but that the level of transformation with DNA lacking a DUS (DUS0) was variable in different strains. The DUS-enhanced transformation was 20-fold in two strains, FA1090 and FA19, but was approximately 150-fold in strains MS11 and 1291. All strains tested provide some level of DUS0 transformation, and DUS0 transformation was type IV pilus dependent. Competition with plasmid DNA revealed that transformation of MS11 was enhanced by the addition of excess plasmid DNA containing a DUS while FA1090 transformation was competitively inhibited. Although FA1090 was able to mediate much more efficient transformation of DNA lacking a DUS than was MS11, DNA uptake experiments showed similar levels of uptake of DNA containing and lacking a DUS in FA1090 and MS11. Finally, DNA uptake was competitively inhibited in both FA1090 and MS11. Taken together, our data indicate that the role of the DUS during DNA transformation is variable between strains of N. gonorrhoeae and may influence multiple steps during transformation.