Caulobacter cultures (strain 3724) were cryofixed using a cocktail of 2% Osmium tetroxide, 0.5% uranyl acetate in anhydrous acetone following this time and temperature schedule: -90 Celsius for 72 hours, raised 2 Celsius per hour for 15 hours, held at -60 Celsius for 12 hours, raised 5 Celsius per hour for 12 hours, held at -20 Celsius. Film images were acquired using a JEOL 4000, at a magnification of 30,000X, 400.0 Kv, with the objective aperture set at 2.