(leapt-toe-thricks) is a filamentous bacteria, sometimes included within the iron bacteria because it lives within an organic tube which becomes encrusted with metal salts and becomes brown with time. The bacteria move forward at the younger end of the tube which is narrower, less substantial and the bacteria seem naked. The other older end of the tube, to the left of the (other) composite image, is broader, more substantial and usually empty - the bacterium progressing as the tube grows. the overall structure may be several hundred of microns long. In this image, the tube has broken to reveal the bacterium inside. Phase contrast.