Stenamoeba dejonckheerei sp. nov., a Free-Living Amoeba Isolated from a Thermal Spring

Two amoeboid organisms were obtained from water samples taken from a thermal spring, Agua Caliente, in Northwestern Mexico. The isolates were obtained when samples were cultivated at 37 degrees C on non-nutrient agar coated withEscherichia coli.The initial identification of the isolates was performed morphologically using light microscopy. The samples were found to have trophozoite morphology consistent with members of the genusStenamoeba, a genus derived in 2007 from within the abolished polyphyletic genusPlatyamoeba. Further analysis was performed by sequencing PCR products obtained using universal eukaryotic primers for the small subunit ribosomal ribonucleic acid (SSU rRNA) gene. Sequencing primers were designed to allow the comparison of the 18S rRNA gene sequences of the new isolates with previous sequences reported forStenamoeba.Phylogenetic relationships among sequences fromStenamoebawere determined using Maximum Likelihood analysis. The results showed the two Agua Caliente sequences to be closely related, while clearly separating them from those of otherStenamoebataxa. The degrees of sequence differentiation from other taxa were considered sufficient to allow us to propose that the Mexican isolates represent a new species.