A century of research on the amoeboflagellate genus Naegleria

Abstract

The amoeboflagellate genus Naegleria contains pathogenic and nonpathogenic species. As most species are morphologically indistinguishable, species are defined and identified by molecular methods. For routine identification, isoenzyme analyses are performed. For the description of a new species, sequences of ribosomal DNA are increasingly used and the analyses of these sequences also allow us to define the phylogenetic relationships between species and strains. In the present monograph 27 Naegleria lineages are discussed and identified as separate species. Using molecular methods, Naegleria spp. have been identified which either form dividing flagellates or which do not form flagellates at all, thus contradicting the accepted definition of the genus. Willaertia, which forms dividing flagellates, is the genus that is the closest relative of the genus Naegleria. The genus Naegleria has some particularities in its molecular biology, such as circular ribosomal DNA plasmids, group I introns in the small and large subunit ribosomal DNA, and an unusual pyrophosphate-dependant phosphofructokinase. The phylogeny of the Naegleria spp. is compared to the situation concerning the other genera of the family Vahlkampfiidae. Also discussed is the state of affairs concerning species designation based on phylogeny in the genus Acanthamoeba, another free-living amoeba with species pathogenic to man.