Abstract
Amoebae have long been thought of as asexual, partially because of their past phylogenetic grouping with “lower organisms” instead of nestled among eukaryotes, where they are today. Several species of amoeba have been shown to recombine sexually, however the sexual activity of Naegleria, an amoeboflagellate, remains in the dark. The Fulton lab has generally worked with the species Naegleria gruberi, studying its differentiation process, where it forms flagella and then reverts into an amoeba. Although no hint of mating has ever been observed in N. gruberi, the Fulton lab, in cooperation with other labs, sequenced and analyzed the genome of N. gruberi and found compelling evidence of sexuality. To understand what may encourage Naegleria to mate, we turned to a relative of N. gruberi called Naegleria minor. Two strains of N. minor were used, WTO43 (“Nami”) and PNG2 (“Ping”). The differentiation pattern of this species had not been extensively studied, but it was known to divide during differentiation. We tested conditions for the cells and dissected their differentiation. Using a low O2-high CO2 gaseous environment, cells maintained in suspension at 28°C produced a satisfactory differentiation at reasonable kinetics. The pattern was found to include at least two irregular divisions, one at 4.5 hours and one between 8 and 24 hours. At 3 hours the cells remain active but lose their culturability, which is only regained under certain conditions. We argue that the differentiation of N. minor is indeed gamete formation, followed under favorable conditions by zygote formation. Future studies include genetic tests of mating and recombination, initially using drug-resistant mutations as markers. From this we hope to establish a new genetic system and perhaps learn more about the ancient origins of sexuality.