The isolation and partial characterization of naturally-evolved outer membrane blebs of Neisseria gonorrhoeae

Abstract

Several Gram negative bacteria form and release outer membrane blebs during growth in vitro, though, little is known about the function or significance of this phenomenon. This study considered naturally-evolved blebs released by Neisseria gonorrhoeae strains JS1 and FA638. The quantity of blebs formed during growth was determined, and blebs were isolated for analysis of protein content and antigenicity. Electron microscopy revealed that blebs were released from organisms during log phase growth. The blebs ranged in size from 70–120 nm in diameter, and blebs harvested at different times appeared to differ in content. Wet mass, UV absorbance, and scanning densitometry determinations showed that JS1, a Protein IB-bearing strain, formed about two times more blebs than did the Protein IA-bearing strain, FA638. Blebs, isolated by differential centrifugation of broth cultures and subjected to sucrose density gradient centrifugation, separated into two bands with densities of 1.12 and 1.30. The protein and antigenic profiles of blebs corresponded to profiles of isolated outer membranes. These results suggests that naturally-evolved membrane blebs contain the same immunogenic and antigenic molecules found in the bacterial outer membrane.