Opa expression correlates with elevated transformation rates in Neisseria gonorrhoeae

Neisseria gonorrhoeae is naturally competent for DNA transformation. Under most conditions encountered in vivo, gonococci express one or more opacity (Opa) proteins on their surfaces. Recently, it was shown that DNA preferentially binds to the surfaces of Opa-expressing organisms compared to those of isogenic Opa-negative strains, presumably due to the numerous cationic residues in the predicted surface-exposed loops of the Opa protein. This study examined whether Opa-DNA interactions actually influence DNA transformation of the gonococcus. The data show that Opa-expressing gonococci are more efficient recipients of DNA for transformation and are more susceptible to exogenous DNase I treatment at early stages during the DNA transformation process than non-Opa expressors. Furthermore, inhibition of the transformation process was demonstrable for Opa(+) populations when either nonspecific DNA or the polyanion heparin was used. Overall, the data suggest that Opa expression, with its presumptive positive surface charge contribution, promotes DNA transformation by causing a more prolonged sequestration of donor DNA at the cell surface, which translates into more efficient transformation over time.