Acanthamoeba differentiation: a two-faced drama of Dr Jekyll and Mr Hyde.

The ability of cyst-forming protists such as Acanthamoeba to escape death by transforming into a cyst form, that is resistant to harsh physiological, environmental and pharmacological conditions, has continued to pose a serious challenge to human and animal health. A complete understanding of the fundamental principles of genome evolution and biochemical pathways of cellular differentiation offers unprecedented opportunities to counter detrimental outcomes. Acanthamoeba can elude inhospitable conditions by forming cysts.

Carbohydrate analysis of Acanthamoeba castellanii.

We analyzed biochemically Acanthamoeba castellanii trophozoites, intact cysts and cyst walls belonging to the T4 genotype using gas chromatography combined with mass spectrometry. Cyst walls were prepared by removing intracellular material from cysts by pre-treating them with sodium dodecyl sulphate (SDS) containing dithiothreitol, and then subjecting these to a series of sequential enzymatic digestions using amyloglucosidase, papain, DNase, RNase and proteinase K. The resulting "cyst wall" material was subsequently lyophilized and subjected to glycosyl composition analysis.

The role of proteases in the differentiation of Acanthamoeba castellanii.

Proteases are significant determinants of protozoan pathogenicity and cytolysis of host cells. However, there is now growing evidence of their involvement in cellular differentiation. Acanthamoeba castellanii of the T4 genotype elaborates a number of proteases, which are inhibited by the serine protease inhibitor phenylmethylsulphonyl fluoride.

Role of human tear fluid in Acanthamoeba interactions with the human corneal epithelial cells.

Acanthamoeba keratitis is a painful and progressive sight-threatening infection. However, the precise mechanisms associated with the pathogenesis and pathophysiology of Acanthamoeba keratitis remain incompletely understood. Using tears from healthy individuals and an Acanthamoeba keratitis patient, we demonstrated that both subjects exhibited similar levels of Acanthamoeba-specific IgA as demonstrated by Western blotting and enzyme-linked immunosorbent assays.

Cellulose biosynthesis pathway is a potential target in the improved treatment of Acanthamoeba keratitis.

Acanthamoeba is an opportunistic protozoan pathogen that can cause blinding keratitis as well as fatal granulomatous encephalitis. One of the distressing aspects in combating Acanthamoeba infections is the prolonged and problematic treatment. For example, current treatment against Acanthamoeba keratitis requires early diagnosis followed by hourly topical application of a mixture of drugs that can last up to a year.

Escherichia coli interactions with Acanthamoeba: a symbiosis with environmental and clinical implications.

The ability of Acanthamoeba to feed on Gram-negative bacteria, as well as to harbour potential pathogens, such as Legionella pneumophila, Coxiella burnetii, Pseudomonas aeruginosa, Vibrio cholerae, Helicobacter pylori, Listeria monocytogenes and Mycobacterium avium, suggest that both amoebae and bacteria are involved in complex interactions, which may play important roles in the environment and in human health. In this study, Acanthamoeba castellanii (a keratitis isolate belonging to the T4 genotype) was used and its interactions with Escherichia coli (strain K1, a cerebrospinal fluid isolate from a meningitis patient, O18 : K1 : H7, and a K-12 laboratory strain, HB101) were studied. The invasive K1 isolate exhibited a significantly higher association with A.

Acanthamoeba isolates belonging to T1, T2, T3, T4 but not T7 encyst in response to increased osmolarity and cysts do not bind to human corneal epithelial cells.

Acanthamoeba is an opportunistic protozoan that is widely distributed in the environment and can cause human infections. The life cycle of Acanthamoeba consists of an infective trophozoite form. However under harsh environmental conditions trophozoites differentiate into a double-walled, metabolically inactive and resistant cyst form.

Mechanisms associated with Acanthamoeba castellanii (T4) phagocytosis.

Using fluorescein isothiocyanate (FITC)-labelled Escherichia coli, phagocytosis in Acanthamoeba is studied. This assay is based on the quenching effect of trypan blue on FITC-labelled E. coli.