Acanthamoeba

Acanthamoeba Volkonsky, 1931 (ref. ID; 36877, 7298, 7358, 7710) reported year? (ref. ID; 1618)

Phylum Rhizopoda Von Siebold, 1845: Class Lobosa Carpenter, 1861: Order Acanthopodina Page, 1976: Family Acanthamoebidae Sawyer & Griffin, 1977 (ref. ID; 7298, 7358)
Order Acanthopodida Page, 1976 (ref. ID; 6789)

[ref. ID; 177]
Members of the genus Acanthamoeba are ubiquitous freshwater and soil amoebae that occur world-wide. During the last decade (1982~), these amebae have been isolated with increasing frequency from contact lens paraphernalia as well as from human tissue such as corneal scrapings and the central nervous system (Ma et al. 1990; Visvesvara & Stehr-Green 1990). Acanthamoeba can be readily recognized because of the striking morphologic characteristics of the trophozoites and cysts. Based on the size and morphologic features of cysts, Pussard & Pons (1977) established 18 species and placed of them in three groups. Group 1 now consists of four species (A. astronyxis, A. comandoni, A. echinulata, and A. tubiashi) characterized by large trophozoites and cysts (>/_ 18 um) (Page 1988; Visvesvara 1991). Species in groups 2 and 3 are smaller (< /_ 18 um) but can be separated from each other on the basis of cyst morphology. Group 2 comprises 10 species (A. castellanii, A. polyphaga, A. rhysodes, A. mauritaniensis, A. divionensis, A. griffini, A. lugdunensis, A. quina, A. hatchetti, and A. triangularis), and five species (A. culbertsoni, A. lenticulata, A. palestinensis, A. pustulosa, and A. royreba) are in group 3 (Page 1988; Visvesvara 1991). Although cyst characteristics make genus identification easy, differentiation to the species level is difficult. This is especially true for members of groups 2 and 3 which cannot always be identified by species on a morphologic basis alone. As a result, the most recent identification attempts have been based on both morphologic and biochemical criteria such as isoenzymes, antigens, protein profiles, and restriction fragment-length polymorphism analysis of DNA resolved by electrophoretic methods (Byers et al. 1983; DeJonckheere 1983; Page 1988; Visvesvara 1991). Cladistic analysis of the data has also been used to elucidate the affinities of the various species of Acanthamoeba (Dagget et al. 1985). (ref. ID; 177)

[ref. ID; 1618]
Small amoebae similar to Hartmannella; ectoplasm is not well developed; mitotic figure at the end of metaphase, a straight or concave spindle with sharply pointed poles. Cysts enveloped by 2 membranes, the outer envelope being highly wrinkled and mammillated. Several species. Neff (1957) obtained axenic cultures of a species from soil. The presence of Acanthamoeba in tissue cultures of trypsinized monkey-kidney cells has been reported by several observers since 1957. (ref. ID; 1618)

[ref. ID; 3701]
The classification of the small soil and freshwater amoebae, particularly those assigned to the genus Acanthamoeba, has been based entirely on the organisation of the nucleus (Singh 1951, 1952; Singh & Das 1970) or on the structure of the trophozoite or cyst (Page 1967, 1976). Comparisons of a wide range of strains using immunological (Willaert 1976), genetic (Adam & Blewett 1974) and physiological techniques (Adam 1064; Griffiths, Curnick, Unitta & Wilcox 1978) have, however, indicated that morphological criteria are not adequate for estimating taxonomic relationships between these organisms. (ref. ID; 3701)

[ref. ID; 3991]
Type species; Acanthamoeba castellanii (Douglas, 1930) (ref. ID; 3991)

[ref. ID; 4022]
Trophozoites of the different species of Acanthamoeba are difficult to identify because of the absence of distinctive morphologic features. The shape and the structure of cysts, on the other hand, differ considerably among the species and can be used as valid taxonomic criteria. (ref. ID; 4022)

[ref. ID; 7430]
Acanthamoeba has been isolated from air, soil, freshwater, saltwater, wild animals and humans. Identification of amoebae from the genus Acanthamoeba is relatively easy after they have been grown in culture. Classification at the subgenus level is a problem, however, even for expert taxonomists. (Visvesvara 1991). The nomenclature and taxonomy of Acanthamoeba have been revised many times (Visvesvara 1991), most recently ~20 years ago (Pussard & Pons 1977; Sawyer & Griffin 1975). Pussard and Pons divided the genus into three morphological groups based on cyst size and shape. Group 1 species have large cysts compared to the other groups, with a smooth ectocyst and stellate endocyst. Group 2 species have a wrinkled ectocyst and the endocyst can be stellate, polygonal, triangular, or oval. Group 3 species typically have a thin, small ectocyst with a round endocyst. However, Sawyer first observed that ionic strength of the growth medium can alter the shape of cysts walls (Sawyer 1971), thus, substantially reducing the reliability of cyst morphology as a taxonomic charateristic. Pussard and Pods (1977) used the number of ostioles in the cysts as defining characters, but this character has been mentioned infrequently in subsequent descriptions of species. In the last decade, several groups have used analysis of isoenzyme electrophoretic patterns to address intrageneric relatioships and to test the morphological classification scheme. These studies discoverd extensive diversity among isolates of Acanthamoeba as exhibited by unique isoenzyme patterns, especially for group 1 species. Moura, Wallace and Visvesvara (1992) found good agreement between isoenzyme patterns and morphological groups, but their study was limited and included only one group 2 isolate, A. castellanii Castellani. De Jonckheere (1983), Daggett et al. (1983), and Costas and Griffiths (1986), studied larger groups of isolate including 30, 71 and 37 strains, respectively. Each study divided isolated of Acanthamoeba into several different groups that often were inconsistent with species and/or morphological group designations. Each study suggested a need for revision of the classification. Analyses of Acanthamoeba mitochondrial DNA restriction fragment length polymorphisms (mtRFLP), although limited in number of isolates used, also revealed a large degree of interstrain genetic diversity (Bogler et al. 1983; Yagita & Endo 1990). Species belonging to groups 2 and 3, especially A. castellanii and A. polyphaga, were shown to be polyphyletic. Isoenzyme patterns and mtRFLP analyses have highlighted ambiguities in the morphology-based classification scheme, but neither approach directly addressed the phylogeny of Acanthamoeba. Johnson et al. (1990) analyzed partial nuclear 18S rRNA sequences from seven isolated of Acanthamoeba and obtained results that were concordant with the classification of Pussard and Pons, but only five species were included. Our lab recently began an investigation of 18S rRNA gene (Rns) phylogeny using 18 isolates of Acanthamoeba from morphological groups 2 and 3 (Gast et al. 1996). (ref. ID; 7430)

[ref. ID; 7714]
The classification of Acanthamoeba at the species level is unsatisfactory in that there are poor correlations between morphology and physiological (Adam 1964; Griffiths, Curnick, Unitt and Wilcox 1978), genetic (Adam and Blewett 1974), immunological (Visvesvara and Balamuth 1975; Willaert and Jadin 1974) and biochemical (Costas and Griffiths 1980) characters. The fatty acid profiles (22 fatty acid methyl acid methyl esters) of the strains varied from batch to batch and at different growth temperatures to such an extent that it was not possible to distinguish between the species. (ref. ID; 7714)

  1. Acanthamoeba astronyxis (Ray & Hayes, 1954) (ref. ID; 299) reported year? (ref. ID; 1543) reported author and year? (ref. ID; 177, 3701, 3985, 4181, 4218, 7430)
  2. Acanthamoeba castellanii Douglas, 1930 (ref. ID; 3687) reported year? (ref. ID; 1543, 1618, 3847) or (Douglas) Volkonsky (ref. ID; 1335) reported author and year? (ref. ID; 177, 3701, 4110, 4158, 4173, 4181, 4218, 4325, 4694, 6791, 7430)
    Syn; Hartmanella rhysodes Singh, 1952 (ref. ID; 4694) reported year? (ref. ID; 4158, 4173)
  3. Acanthamoeba comandoni (ref. ID; 177, 3793, 7430)
  4. Acanthamoeba culbertsoni (Singh & Das) (ref. ID; 3847) reported author and year? (ref. ID; 177, 3639, 4110, 7430)
  5. Acanthamoeba divionensis (ref. ID; 177, 4110)
  6. Acanthamoeba echinulata (ref. ID; 177)
  7. Acanthamoeba griffini Sawyer, 1971 (ref. ID; 7358) reported author and year? (ref. ID; 177, 4110, 4158, 4181, 4218, 4694, 7430, 7661)
  8. Acanthamoeba hatchetti Sawyer (ref. ID; 3847) reported author and year? (ref. ID; 177, 4110, 4181, 7430)
  9. Acanthamoeba healyi Moura, Wallace & Visvesvara, 1992 (ref. ID; 177 original paper, 7430)
  10. Acanthamoeba hyalina Dobell & O'Conner, 1921 (ref. ID; 3687) reported year? (ref. ID; 1618)
  11. Acanthamoeba jacobsi Sawyer et al., 1992 (ref. ID; 7358)
  12. Acanthamoeba lenticulata (ref. ID; 177, 4110, 7430)
  13. Acanthamoeba lugdunensis (ref. ID; 177, 4110, 7430)
  14. Acanthamoeba mauritaniensis (ref. ID; 177, 4110)
  15. Acanthamoeba palestinensis (Reich, 1933) (ref. ID; 4090) or (Reich, 1933) Page, 1967 (ref. ID; 3767) reported author and year? (ref. ID; 177, 3701, 4022, 4110, 4181, 4218, 7430)
    Syn; Mayorella palestinensis Reich, 1933 (ref. ID; 3767)
  16. Acanthamoeba paradivionensis (ref. ID; 4110)
  17. Acanthamoeba pearcei Nerad et al., 1995 (ref. ID; 7358 original paper) reported author and year? (ref. ID; 7430)
  18. Acanthamoeba polyphaga Puschkarew, 1913 (ref. ID; 4105) reported year? (ref. ID; 1543, 3847) reported author and year? (ref. ID; 177, 3639, 3701, 4110, 4158, 4181, 4218, 4258, 4694, 7430)
  19. Acanthamoeba pustulosa (ref. ID; 177, 4110, 7430)
  20. Acanthamoeba quina (ref. ID; 177, 4110)
  21. Acanthamoeba rhysodes (Singh, 1952) (ref. ID; 4269) reported year? (ref. ID; 3847) reported author and year? (ref. ID; 177, 3639, 3701, 4110, 4181, 4218, 7430)
  22. Acanthamoeba royreba Willaert, Stevens & Tyndall, 1978 (ref. ID; 3805 original paper, 4110) reported author and year? (ref. ID; 177)
  23. Acanthamoeba stevensoni Sawyer, Nerad, Lewis & Mclaughlin, 1993 (ref. ID; 7298 original paper, 7358, 7430)
  24. Acanthamoeba terricola (ref. ID; 4181, 4218)
  25. Acanthamoeba triangularis (ref. ID; 177)
  26. Acanthamoeba tubiashi (ref. ID; 177, 7430)

Acanthamoeba astronyxis (Ray & Hayes, 1954) (ref. ID; 299) reported year? (ref. ID; 1543) reported author and year? (ref. ID; 177, 3701, 3985, 4181, 4218, 7430)

Descriptions


Acanthamoeba castellanii Douglas, 1930 (ref. ID; 3687) reported year? (ref. ID; 1543, 1618, 3847) or (Douglas) Volkonsky (ref. ID; 1335) reported author and year? (ref. ID; 177, 3701, 4110, 4158, 4173, 4181, 4218, 4325, 4694, 6791, 7430)

Synonym

Hartmanella rhysodes Singh, 1952 (ref. ID; 4694) reported year? (ref. ID; 4158, 4173)

Descriptions

In association with fungi and certain bacteria; Hewitt obtained the organism from agar cultures of sample soil taken from among the roots of white clover; co-existing with yeast-like fungi, Flavobacterium trifolium and Rhizobium sp.; some cysts are said to remain viable at 37 degrees C for 6 days. (ref. ID; 1618)
Marine amoeba. (ref. ID; 3847)
Acanthamoeba castellanii is a free-living organisms, found in soil and fresh water, which forms a dormant, non-reproductive cysts. The cyst has a thick, wrinkled outer wall and a cellulose-containing inner wall. The outer wall is resistant to chemical and physical analysis so that little is known about its composition and molecular organization. (ref. ID; 4173)

Measurements

12-30 um in diameter. (ref. ID; 1618)

Available culture

Acanthamoeba castellanii Neff strain (ATCC 30010). Genome sequence. (ref. ID; 6791)

Acanthamoeba hatchetti Sawyer (ref. ID; 3847) reported author and year? (ref. ID; 177, 4110, 4181, 7430)

Descriptions

Marine amoebae. (ref. ID; 3847)

Acanthamoeba hyalina Dobell & O'Conner, 1921 (ref. ID; 3687) reported year? (ref. ID; 1618)

Descriptions

According to Volkonsky, the organism described by Dobell & O'Conner as Hartmannella hyalina, is transferred to this genus. Small amoeba; a single contractile vacuole; binary fission; mitotic figure a sharply pointed spindle. Cysts spherical; with a smooth inner and a much wrinkled outer wall; easily cultivated from old faeces of man and animals; also in soil and fresh water. (ref. ID; 1618)

Measurements

9-17 um in diameter when rounded; cyst 10-15 um in diameter. (ref. ID; 1618)

Acanthamoeba palestinensis (Reich, 1933) (ref. ID; 4090) or (Reich, 1933) Page, 1967 (ref. ID; 3767) reported author and year? (ref. ID; 177, 3701, 4022, 4110, 4181, 4218, 7430)

Synonym

Mayorella palestinensis Reich, 1933 (ref. ID; 3767)

Descriptions

Comments

The inner and outer walls of the cyst of A. palestinensis have almost the same fine structure, while in A. castellanii they differ considerably (Bowers & Korn 1969). The endocyst of A. palestinensis is nearly rounded, the few ostioles are located anywhere, and the operculum is flat and close to the protoplast surface. In A. castellanii, on the other hand, the endocyst is star-shaped with several truncated rays, the ostioles are located at the edges of the rays, and the operculum is thick, arched and further away from the cell surface. (ref. ID; 4022)

Acanthamoeba pearcei Nerad et al., 1995 (ref. ID; 7358 original paper) reported author and year? (ref. ID; 7430)

Diagnosis

Trophozoites typical of the genus Acanthamoeba Volkonsky, 1931. Locomotive forms 25.0-42.5 um long (average=3.1) by 17.5-25.0 um wide (average=22.1) and feeding forms approximately as wide as long. Amoebae contract in presence of light or heat from the microscope altering typical features of locomotive and feeding forms. Fixed and stained specimens approximately 22.5-39.0 um long (mean 27.9) by 12.5-17.5 um wide (average=14.7); nucleus 3.5-4.0 um (average=3.5). Living cysts 17.5-25.0 um in diameter (average=20.5). Ectocyst smooth without depressions at tips of arms or rays of the endocyst. Endocysts with 3-7 rays or arms, rarely 8-9, that are deeply scalloped with blunt or rounded tips. Acanthamoeba pearcei, strain ATCC 50435 did not grow at 37-39 degrees C, and was not pathogenic to laboratoy mice via the intranasal route. (ref. ID; 7358)

Isoenzyme profiles

Zymograms for propionyl esterase (PE), leucine aminopeptidase (LA) and acid phosphatase (AP) by enzyme electrophoresis were distinct for A. pearcei (ATCC 50435) and morphologically similar A. astronyxis (ATCC 30137). The PE zymogram for A. pearcei had seven bands compared to five bands for A. astronyxis with only one band shared by both species. The zymograms for LA had a single band with that of A. pearcei being more anodal than that of A. astronyxis. The AP zymogram for A. pearcei had one discrete anodal band and two cathodal bands in contrast to six anodal and two cathodal bands for A. astronyxis. The single anodal band for A. pearcei appeared to be shared with one of the two anodal bands for A. astronyxis. Twenty-one bands were expressed by the two strains, but only four (19%) were shared. (ref. ID; 7358)

Notes

There are several species of Acanthamoeba, that are not readily identifiable solely on the basis of their morphological features. Pussard and Pons (1977) proposed that each species be placed into one of three groups on the basis of cyst morphology in order to facilitate preliminary identification. Group 1 was proposed for species with distinctly scalloped endocysts, including A. astronyxis, A. comandoni, and A. echinulata. Acanthamoeba pearcei clearly belongs to Group 1, most closely resembling A. astronyxis. The principle characteristics for distinguishing between the two are the features of their cysts and their distinctly different zymograms. The new species, A. pearcei, is the fifth species originally isolated from marine or brackish waters. The first, A. griffini, was found in Long Island Sound, New York (Sawyer 1971), the second, A. hatchetti, from Baltimore Harbor, MD (Sawyer et al. 1977), the third, A. jacobsi, from the discontinued New York 12-Mile nearshore waste disposal site (Sawyer et al. 1992), and the fourth, A. stevensoni, from contaminated shellfish beds near Staten Island, New York (Sawyer et al. 1993). Acanthamoeba hatchetti and A. stevensoni were highly pathogenic to mice, and A. jacobsi mildly pathogenic. Acanthamoeba griffini and A. pearcei were not pathogenic under the conditions tested and neither grew when incubated at 39-40 degrees C. (ref. ID; 7358)

Type locality

Sewage contaminated ocean sediments from the northeast Atlantic Ocean, 65 km offshore from Maryland and Delaware, USA, approximately 38 degrres 19.6'N, 74 degrees 18.0'W. (ref. ID; 7358)

Type strain

Deposited at the American Type Culture Collection, Rockville, Maryland 20852, Accession no. ATCC 50435. (ref. ID; 7358)

Acanthamoeba polyphaga Puschkarew, 1913 (ref. ID; 4105) reported year? (ref. ID; 1543, 3847) reported author and year? (ref. ID; 177, 3639, 3701, 4110, 4158, 4181, 4218, 4258, 4694, 7430)

Descriptions

Marine amoebae. (ref. ID; 3847)

Acanthamoeba rhysodes (Singh, 1952) (ref. ID; 4269) reported year? (ref. ID; 3847) reported author and year? (ref. ID; 177, 3639, 3701, 4110, 4181, 4218, 7430)

Descriptions

Marine amoebae. (ref. ID; 3847)

Acanthamoeba royreba Willaert, Stevens & Tyndall, 1978 (ref. ID; 3805 original paper, 4110) reported author and year? (ref. ID; 177)

Descriptions


Acanthamoeba stevensoni Sawyer, Nerad, Lewis & Mclaughlin, 1993 (ref. ID; 7298 original paper, 7358, 7430)

Diagnosis

Trophozoites typical of the genus Acanthamoeba Volkonsky, 1931. Growth at 38-40 degrees C, and pathogenic to laboratory mice. Amoebae in locomotion often seen with a stretched adhesion uroid or collopodium with tufts of short spiny processes. Cysts irregularly rounded with polygonal or bluntly stellate endocyst. The ectocyst wall is single, refractile, slightly rippled, and not inflated or circular. Contour of the ectocyst similar to that of polygonal endocysts, irregularly rounded in stellate endocysts with blunt arms. (ref. ID; 7298)

Type locality

Sewage-contaminated sediments from hard clam beds (Mercenaria mercenaria), in Raritan Bay, New York near Staten Island, approximately 70 degrees 07'8" longitude and 40 degrees 30'05" latitude. (ref. ID; 7298)

Type specimens

Deposited at the American Type Culture Collection, Rockville, Maryland 20852, Accession No. ATCC 50388. (ref. ID; 7298)

Measurements

Length 27.5-42.5 um (mean 33.9) and width 15.0-20.0 long (mean 17.6) in the living condition. Fixed and stained amoebae 22.5-32.5 um long (mean 29.7) and 15.0-20.0 wide (mean 17.1). Nucleus 3.5-4.0 um in diameter. Living cysts 10.0-22.5 um (mean 16.5). (ref. ID; 7298)