Hartmannella Culbertsoni as Revealed in Scanning Electron Microscopy

An axenic culture of Hartmannella culbertsoni obtained from the American Type Culture Collection was used in this study. Amoebas maintained in a trypticase soy broth medium were concentrated, fixed and dehydrated before being transferred drop-wise to round microscope cover classes for critical point drying in liquid CO2. Dried specimens were coated with carbon and palladium-gold and studied with an SEM. H. culbertsoni showed extreme polymorphism. Surface specializations or microappendages, not previously demonstrated in the light microscope, were observed. Some of the amoebas possessed smooth cellular surfaces with scattered bleb-like and bulbous ectoplasmic projections and others had irregular surface contours with threadlike processes of varying lengths. Other cells exhibited finger-like projections which formed a fringe over most of the surface. Such advanced pleomorphism, under identical environmental conditions, depends on the phase of growth, differential adhesion and locomotion of cells. OHIO J. SCI. 76(4): 167, 1976 Free-living soil amoebas or Acanthamoeba (Butt, 1966) have been difficult to describe by light microscopy, and as a result disagreement and confusion concerning their taxonomy prevail in the voluminous literature. The disagreement is due mainly to different views about taxonomic criteria (F. C. Page, personal communication). According to Page (1967b), the erosion of the taxonomic line between the free-living and parasitic amoebas has been responsible for the difficulty encountered in dealing with the subclass Rhizopoda (phylum Protozoa). The evolution of the taxonomic problem began when Jahnes, Fullmer and Li (1957) found a small amoeba classified as Acanthamoeba in monkey tissue culture cells. Later Culbertson, Smith and Minner (1958) observed a similar amoeba in tissue culture fluid suspected of having an unknown simian virus. When this tissue culture fluid was injected into the brains of mice and monkeys, only freeliving amoebas identified as Acanthamoeba were found in resulting lesions of severe primary meningoencephalitis. These motile amoebas were designated Manuscript received March 22, 1976 and in revised form April 20, 1976 (#76-29). as Harlmannella by Singh and Das (1970). After finding several other hartmannellid amoebas which were identical, they proposed the new species Hartmannella