Abstract: An assembly is provided for the culturing of aerogenic microorganisms. It includes a culture bottle having a neck portion defining an opening therein. A lip is provided near the bottle opening and a stopper is positioned within the opening. A stopper lock is mounted on the bottle neck to prevent the stopper from blowing off due to pressure generated within the bottle. The lock is capable of limited movement along the neck, however, to allow the stopper to rise to a height which allows venting of the bottle. The stopper lock includes an inwardly extending upper flange, an inwardly extending lower flange, and sidewalls interconnecting the flanges. The upper flange is capable of engaging the upper surface of the stopper while the lower flange is capable of engaging the lower surface of the lip. The stopper lock is movable along the neck between positions of engagement with the upper surface of the stopper and the lower surface of the lip.