and human pathology
are ubiquitous and so abundant, is it hardly surprising that they have been connected with
various human diseases. Although these amoebae cause a very serious life threatening
disease , this is exceptionally rare. More common is keratitis, a disease associated
with contact lens use and (more often), abuse. Acanthamoeba together with
several other amoeba are parasitised by various bacteria (Fig 2). This is
from the point of human health because one of these is Legionella, a bacterium
that has caused serious outbreaks. Legionella, itself not a robust bacteria
survives harsh conditions by becoming encased within the resistant cyst of Acanthamoeba
and Hartmannella (See Pathogenesis
Acanthamoeba feeds on micro-organisms in
bio-films, usually on surfaces (Brown &
Barker, 1999) but even at the
air-water interface (Preston et al,
2001). The Acanthapodia, finger-like
projections arising from the leading edge and transported over the cell
surface rearwards may be involved in the feeding process by increasing
surface area with which to capture suitable prey (Figure 1). Acanthamoeba
detects prey items by chemotaxis (). Prey items
are usually bacteria (Upadhyay et al,
1968; Weekers et
al, 1993) but algae (Wright
et al, 1981) yeast (Allen
& Dawidowicz, 1990 )
and other protist are sometimes
Allen, P. G. & Dawidowicz, E. A.
(1990) Phagocytosis in Acanthamoeba: 1. A mannose receptor is
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Unexplored reservoirs of pathogenic bacteria: protozoa and biofilms. Trends
Microbiol. 7, 46-50.
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Habte, M. & Alexander, M. (1978)
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protozoa. Soil Biol. Biochem. 10, 1-6.
Kingston, D. & Warhurst, D. C.
(1969) Isolation of amoebae from the air. J.Med.Microbiol. 2,
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J. & Laybourn-Parry, J. (1998) Temporal abundance of naked bactivore
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Page, F. C. (1981) A light- and
electron-microscopic study of Protoacanthamoeba caledonica n.sp.,
type-species of Protoacanthmaoeba n. g. (Amoebida, Acanthamoebidae).,
J.Protozool. 28, 70-78.
Preston, T. M., Richard, H. & Wotton,
R. S. (2001) Locomotion and feeding of Acanthamoeba at the
water-air interface of ponds., FEMS letters. 194, 143-147.
Sawyer, T. K. (1971) Isolation and
identification of free-living marine amoebae from upper Chesapeake bay,
Maryland. Trans.Amer.Micros.Soc. 90, 43-51.
Sawyer, T. K. (1989) Free-living
pathogenic and non-pathogenic amoebae in Maryland soils. App.Environ.Microbiol.
Sawyer, T. K., Visvesvara, G. S. &
Harke, B. A. (1977) Pathogenic amoebas from brackish and oceanic
sediments, with a description of Acanthamoeba hatchetti, n.s p., Science.
Upadhyay, J. M. (1968) Growth and
bacteriolytic activity of a soil amoeba, Hartmannella glebae, J.Bacteriol.
95, 771-774. (This Hartmannella is actually an Acanthamoeba)
Weekers, P. H. H., Bodelier, P. L. E.,
Wijen, J. P. H. & Vogels, G. D. (1993) Effects of grazing by the
free-living soil amoebae, Acanthamoeba catellanii, Acanthamoeba
polyphaga, and Hartmannella vermiformis on various bacteria. App.Environ.Microbiol.
Wright, S. J. L., Redhead, K. &
Maudsley, H. (1981) Acanthamoeba castellanii, a predator of
cyanobacteria. J.Gen.Microbiol. 125, 293-300.