A student is performing an aseptic transfer of a bacterial culture from a stock bottle to an agar plate. The student passes the neck of the glass stock bottle through a Bunsen burner flame immediately after removing the cap, and again just before replacing it.
What is the primary scientific reason for flaming the neck of the culture bottle in this way?
To create an upward convection current of warm air that prevents airborne contaminants from falling into the open bottle.
To sterilise the glass neck by killing all bacterial cells and fungal spores present on the rim.
To evaporate any residual condensation on the lip of the bottle to prevent aerosol formation.
To expand the mouth of the glass bottle slightly so that the screw cap forms a tighter, sterile seal.