Abstracts (first author)
Entamoeba varieties use biochemical signaling and behavioral aggregation to discriminate between members of distinctive strains
Evolutionary processes in which selection acted continuously and cumulatively on ancestors of Entamoeba populations gave rise to chemical and behavioral signals that allowed individuals to discriminate non-population members and, gradually, to the emergence of new lineages. The concept of ‘species recognition’ at the unicellular level might be artificial and inadequate to define signaling in single-cell natural populations. Aggregative behavior could be explored in a nonsocial protist to define discrimination cues among/between natural varieties. We demonstrate that by color tagging and pair-mix-culturing six Entamoeba varieties, the difficulty of discerning among apparently similar taxa can be resolved. When grown together with different amoeba strains, free-living/opportunistic (E. moshkovskii Laredo), commensal (E. moshkovskii Snake) or parasitic (E. invadens IP-1, E. invadens VK-1:NS, E. terrapinae, E. histolytica) trophozoites aggregate only with members of their own lineage. Clusters of trophozoites from each amoeba show distinctive rate of aggregation, density of cells per cluster, and distance between clusters. By using these behavioral cues, and identifying the genes involved in cell-signaling for cluster formation, distinctive amoeba taxa can be characterized quantitatively; we postulate that not only Entamoeba varieties, but apparent taxa crypticity in other protists, can be resolved by examining the natural ability of unicellular eukaryotes to discriminate between members and non-members of a lineage. Thus, phylogenetic relations among protists, which are usually determined by morphology and molecular techniques (the latter often confounded by horizontal gene transfer), could be further understood by incorporating behavior into the evolutionary analysis of this complex group of organisms.