Abstract
Acanthamoeba castellanii is a ubiquitous free-living amoeba. Pathogenic strains are causative agents of Acanthamoeba keratitis and granulomatous amoebic encephalitis. In response to adverse conditions, A. castellanii differentiate into cysts, which are metabolically inactive and resistant cells. This process, also named encystment, involves biochemical and genetic modifications that remain largely unknown. This study characterizes the role of the ACA1_384820 Acanthamoeba gene during encystment. This gene encodes a putative N-acetyltransferase, belonging to the Gcn5-related N-acetyltransferase (GNAT) family. We showed that expression of the ACA1_384820 gene was down-regulated as early as two hours after induction of encystment in A. castellanii. Interestingly, overexpression of the ACA1_384820 gene affects formation of cysts. Unexpectedly, the search of homologs of ACA1_384820 in the Eukaryota gene datasets failed, except for some species in the Acanthamoeba genus. Bioinformatics analysis suggested a possible lateral acquisition of this gene from prokaryotic cells. This study enabled us to describe a new Acanthamoeba gene that is down-regulated during encystment.
Highlights
Acanthamoeba spp. are free-living amoebae, commonly found in diverse natural environments such as soil, water and air, and in artificial facilities including tap water systems, cooling towers, sewage and air conditioning systems [1,2]
lateral gene transfer (LGT)-derived genes are differentially expressed in A. castellanii following the growth phase, under agitation, hypoxia or upon bacterial infections, suggesting their involvement in Acanthamoeba physiology [16]. The contribution of these LGT-derived genes to encystment remains under-investigated. Regarding their importance in cell physiology, we have investigated the role of putative Gcn5-related N-acetyltransferase (GNAT) in the encystment of A. castellanii
The N-Acetyltransferase-Like mRNA Levels Are Down-Regulated during Encystment
Summary
Acanthamoeba spp. are free-living amoebae, commonly found in diverse natural environments such as soil, water and air, and in artificial facilities including tap water systems, cooling towers, sewage and air conditioning systems [1,2]. Pathogenic strains of Acanthamoeba spp. are causative agents of a rare fatal infection of the central nervous system, called granulomatous amoebic encephalitis, and of Acanthamoeba keratitis (AK), a progressive eye disease [3,4]. AK is generally associated with contact lens wearers and remains an elusive problem in spite of advances in antimicrobial chemotherapy and eye care [5]. The formation of cysts, called encystment, is a reversible process that is induced by harsh conditions, such as lack of nutrients, or change in osmotic pressure or pH [6,7]. The cyst represents a resistant and resting form that protects the amoeba against adverse conditions such as heat, freezing and chemicals, and enables it to persist for many years [8,9]
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