|
This
is the genus that most people consider when the word "amoeba"
is mentioned. Amoeba proteus is a so called "giant
amoeba", being large compared to the huge number of other
genera generally considered to belonging to the amoeba. Recent
molecular data (Bolivar et al, 2001)
(SSUrRNA) suggest that Amoeba is most closely related to Chaos
and less so to genera such as Rhizamoeba, Paraflabellula, Leptomyxa,
Hartmanella and Echinamoeba. The
nuclear membrane of Amoeba sp has a honey comb appearance (Goldstein
et al, 1978)
presumably as it is studded with so many nuclear pore complexes.
The nucleus of Amoeba proteus and A. discoides probably
contains histone-like proteins (Sopina
et al, 1979)
as cross reactive proteins have been detected by immuno-fluorescence
using antibodies directed against calf thymus histones. So far the
relationship to other genera of amoeba is a bit of a mystery as little
genetic information is known. The determination of the SSUrDNA
gene of Amoeba will be complicated by the fact that this group
has to be cultured with other protists whose presence may make the unambiguous
isolation of the gene difficult. Saccamoeba another member
of the Family Amoebidae have been analysed at the SSUrDNA level, and if
the family turns out to be valid then we can assume the Amoeba
fits into the general relationship in a similar position (Amaral
Zettler et al, 2000).
A myosin heavy chain gene from Amoeba
proteus has been cloned and sequenced (Oh
& Jeon, 1998) so
this may be used when other sequences become known for other amoeba
genera, so far there are only a handful of amoeba (Acanthamoeba, Dictyostelium
& Entamoeba ) that have conventional myosin genes
sequenced.
Collecting
"Giant" amoeba
|
| References
Amaral Zettler,
L.A., Nerad, T.A., O'Kelly, C.J., Peglar, M.T., Gillevet, P.M.,
Silberman, J.D. & Sogin, M.L. (2000). "A molecular reassessment
of the Leptomyxid amoebae." Protist 151, 275-282.
Bolivar, I., Fahrni, J. F., Smirnov,
A. & Pawlowski, J. (2001) SSU rRNA-based phylogenetic position of
the genera Amoeba and Chaos (Lobosea, Gymnamoebia): The
origin of gymnamoebae revisited. Mol.Biol.Evol. 18, 2306-2314.
Goldstein, L.,
Wise, G.E., Stephenson, C. & Ko, C. (1978). "Small nuclear RNAs:
An association with condensed chromatin in amoebae." J.Cell Sci.
30, 227-235.
Jeon, K.W.
(1995). "Bacterial endosymbiosis in amoebae." Trends Cell
Biol. 5, 137-140.
Oh, S.W. &
Jeon, K.W. (1998). "Characterization of myosin heavy chain and its
gene in Amoeba proteus." J.Euk.Microbiol. 45(6),
600-605.
Prusch, R.D.
& Thompson, V.L. (1994). "Diacyglycerol as a component of the
signal-coupling pathways during the initiation of endocytosis in Amoeba
proteus." Cell & Tissue Res. 279(2), 359-364.
Sopina, V.A.,
Ivanova, S.B., Lipskaya, A.A., Bers, E.P., Vodop'yanova, L.G., Afon'kin,
S.Y. & Kozlov, A.V. (1979). "A study of histones in amoeba
nuclei by indirect immunofluorescence method." Exp.Cell Res.
121, 299-306.
|
