Colorized scanning electron micrograph (SEM) depicts a free-living amoeba (FLA), Vermamoeba (Hartmannella) vermiformis (orange) as it entraps a Legionella pneumophila bacterium (green) with an extended pseudopod. After it is ingested, the Legionella pneumophila bacterium can survive as a symbiont within what then becomes its protozoan host. The amoeba then becomes what is referred to as a "Trojan horse", for by harboring the pathogenic bacteria, the amoeba can afford them protection, and in fact, in times of adverse environmental conditions, are able to metamorphose into a cystic-stage enabling it, and its symbiotic resident pathogens to withstand such environmental stresses.