The cells were post-fixed in 2% osmium tetroxide for 45 min, dehydrated in an acetone series (25%, 50%, 75%, 90%, 100% and dry 100%) and critical point dried. The dried samples were spread over two-sided carbontape on a stub and coated with gold-palladium alloy and examinedunder a Joel JSM 5000 LV Scanning Electron Microscope (SEM).