The invention relates to liposomes, particularly, but not exclusively, to liposomes for introducing a molecule into a cell, and to processes for making and using liposomes. These mycobacteria have a deletion of an RD1 region or a region controlling production of a vitamin, and exhibit attenuated virulence in a mammal when compared to the mycobacteria without the deletion. The manufacturing information may be divided into at least a high group and a low group using a statistical clustering method. The opening 6 is closable by a float device 10, or includes a flow restricting control valve 13. A removable face plate seals shut the front face opening.