Characterization of a Deep-Branching Heterolobosean, Pharyngomonas turkanaensis n. sp., Isolated from a Non-Hypersaline Habitat, and Ultrastructural Comparison of Cysts and Amoebae Among Pharyngomonas Strains.
An unusual heterolobosean amoeba, isolate LO, was isolated recently from a sample with a salinity of ~4‰, from Lake Turkana in East Africa. 18S rDNA phylogenies confirm that isolate LO branches among halophilic amoeboflagellates assigned to Pharyngomonas. We examined the ultrastructure of the amoeba and cyst stages of isolate LO, as well as the amoebae and cysts of Pharyngomonas kirbyi (isolates AS12B and SD1A). The amoebae of all three isolates lacked discrete dictyosomes and had discoidal/flattened mitochondrial cristae, but the mitochondria were not enrobed by rough endoplasmic reticulum. The cysts of all three isolates showed a thick, bipartite cyst wall, and lacked cyst pores. The cysts of isolate LO were distinct in that the ectocyst was very loose-fitting, and could contain "crypts". No flagellate form of isolate LO has been observed to date, and a salinity-for-growth experiment showed that isolate LO can grow at 15-100‰ salinity, indicating that it is halotolerant. By contrast, other studied Pharyngomonas isolates are amoeboflagellates and true halophiles. Therefore, we propose isolate LO as a new species, Pharyngomonas turkanaensis n. sp. It is possible that P. turkanaensis descended from halophilic ancestors, and represents a secondary reestablishment of a physiology adapted for moderate salinity.
Department of Oceanography and Kyungpook Institute of Oceanography, School of Earth System Sciences, Kyungpook National University, Daegu, Korea.
Jong Soo
JS
Park
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.|Canadian Institute for Advanced Research, Program in Integrated Microbial Diversity, Toronto, Ontario, Canada.
Alastair G B
AG
Simpson
D000818:Animals; D056890:Eukaryota / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000648:ultrastructure; D010802:Phylogeny; D054712:Salinity
Amoeboflagellate; electron microscopy; excavata; halophile; halotolerant; protist; protozoa; taxonomy