Growth, Reproduction, and Differentiation in Acanthamoeba

Byers, Thomas J.

doi:10.1016/s0074-7696(08)62000-8

Cited by 67 publications

(29 citation statements)

References 147 publications

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“…Generally, the amebae are uninucleate, although multinucleated cells are common when Acanthamoeba are maintained in suspension culture. Reproduction occurs by binary fission (59,340).…”

Section: Morphologymentioning

confidence: 99%

Acanthamoebaspp. as Agents of Disease in Humans

2003

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Acanthamoeba spp. are free-living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin-embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease

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“…Generally, the amebae are uninucleate, although multinucleated cells are common when Acanthamoeba are maintained in suspension culture. Reproduction occurs by binary fission (59,340).…”

Section: Morphologymentioning

confidence: 99%

Acanthamoebaspp. as Agents of Disease in Humans

2003

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“…Unfavorable environment conditions, such as high temperatures and pH, nutrient depletion, and osmotic stress, have been shown to induce encystation (41,42); thus, it is unclear why sGW incubation of A. polyphaga, A. castellanii, and V. vermiformis resulted in maintenance of the trophozoite form given the relatively low nutrient components in the sGW medium. For A. castellanii, the failure to encyst has been described previously by Stöhr, who reported that 5 to 8% of exponentially growing cells encysted after a 72 h of nutrient starvation compared to 70% of stationary-phase cells after 30 h of starvation (43).…”

Section: Discussionmentioning

confidence: 99%

Exposure to Synthetic Gray Water Inhibits Amoeba Encystation and Alters Expression of Legionella pneumophila Virulence Genes

Buse

Ashbolt

2015

Appl Environ Microbiol

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bWater conservation efforts have focused on gray water (GW) usage, especially for applications that do not require potable water quality. However, there is a need to better understand environmental pathogens and their free-living amoeba (FLA) hosts within GW, given their growth potential in stored gray water. Using synthetic gray water (sGW) we examined three strains of the waterbased pathogen Legionella pneumophila and its FLA hosts Acanthamoeba polyphaga, A. castellanii, and Vermamoeba vermiformis. Exposure to sGW for 72 h resulted in significant inhibition (P < 0.0001) of amoebal encystation versus control-treated cells, with the following percentages of cysts in sGW versus controls: A. polyphaga (0.6 versus 6%), A. castellanii (2 versus 62%), and V. vermiformis (1 versus 92%), suggesting sGW induced maintenance of the actively feeding trophozoite form. During sGW exposure, L. pneumophila culturability decreased as early as 5 h (1.3 to 2.9 log 10 CFU, P < 0.001) compared to controls (⌬0 to 0.1 log 10 CFU) with flow cytometric analysis revealing immediate changes in membrane permeability. Furthermore, reverse transcription-quantitative PCR was performed on total RNA isolated from L. pneumophila cells at 0 to 48 h after sGW incubation, and genes associated with virulence (gacA, lirR, csrA, pla, and sidF), the type IV secretion system (lvrB and lvrE), and metabolism (ccmF and lolA) were all shown to be differentially expressed. These results suggest that conditions within GW may promote interactions between water-based pathogens and FLA hosts, through amoebal encystment inhibition and alteration of bacterial gene expression, thus warranting further exploration into FLA and L. pneumophila behavior in GW systems. G ray water (GW) usage has proven to be both an economically and a logistically suitable solution to alleviate the stresses from increasing potable water demand and climate/demographic change (1), when used (following adequate treatment) in largeand small-scale irrigation, toilet flushing, and car washing (2-4). Defined as household wastewater that is not contaminated with toilet waste, GW is further categorized as light (derived from bathroom showers, tubs, and washbasins) and dark (derived from laundry machines, dishwashers, and kitchen sinks) gray water (5). In households surveyed internationally, light GW constitutes about 47% of total GW, with the remaining 27 and 26% originating from kitchen sinks/dishwashers and laundry washing machines, respectively (reviewed in reference 5). The composition of GW varies greatly with light GW containing mostly personal care products and dark GW composed mostly of dish and laundry detergents, food residue, and fats, oils, and grease.Few studies report on the densities of microbial contaminants within treated GW, and of these, most present fecal indicator data, with less information on pathogens (6). When reusing GW there is concern for fecally borne pathogens (such as species in the bacterial genera Campylobacter, Salmonella, and Vibrio [7-10]), as well as an emerg...

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“…Starvation is a major signal for encystment in FLA (46,50), and it also induces encystment or differentiation in other amoebae, such as Entamoeba and Dictyostelium spp. Osmotic stress also clearly induces encystment of Acanthamoeba, and this is true for osmotic stress induced by various compounds like salts and glucose (6,12,18).…”

Section: Signals and Signaling Pathwaysmentioning

confidence: 95%

Cellular, Biochemical, and Molecular Changes during Encystment of Free-Living Amoebae

Fouque

Trouilhé

Thomas³

et al. 2012

Eukaryot Cell

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ABSTRACTFree-living amoebae are protozoa found in soil and water. Among them, some are pathogenic and many have been described as potential reservoirs of pathogenic bacteria. Their cell cycle is divided into at least two forms, the trophozoite and the cyst, and the differentiation process is named encystment. As cysts are more resistant to disinfection treatments than trophozoites, many studies focused on encystment, but until recently, little was known about cellular, biochemical, and molecular modifications operating during this process. Important signals and signaling pathways at play during encystment, as well as cell responses at the molecular level, have been described. This review summarizes our knowledge and focuses on new findings.

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Growth, Reproduction, and Differentiation in Acanthamoeba

Cited by 67 publications

References 147 publications

Acanthamoebaspp. as Agents of Disease in Humans

Acanthamoebaspp. as Agents of Disease in Humans

Exposure to Synthetic Gray Water Inhibits Amoeba Encystation and Alters Expression of Legionella pneumophila Virulence Genes

Cellular, Biochemical, and Molecular Changes during Encystment of Free-Living Amoebae

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