Phagocytosis-associated genes in Acanthamoeba castellanii feeding on Escherichia coli

Abstract

Acanthamoeba species are free-living amoebae those are widely distributed in the environment. They feed on various microorganisms, including bacteria, fungi, and algae. Although majority of the microbes phagocytosed by Acanthamoeba spp. are digested, some pathogenic bacteria thrive within them. Here, we identified the roles of 3 phagocytosis-associated genes (ACA1_077100, ACA1_175060, and AFD36229.1) in A. castellanii. These 3 genes were upregulated after the ingestion of Escherichia coli. However, after the ingestion of Legionella pneumophila, the expression of these 3 genes was not altered after the consumption of L. pneumophila. Furthermore, A. castellanii transfected with small interfering RNS (siRNA) targeting the 3 phagocytosis-associated genes failed to digest phagocytized E. coli. Silencing of ACA1_077100 disabled phagosome formation in the E. coli-ingesting A. castellanii. Alternatively, silencing of ACA1_175060 enabled phagosome formation; however, phagolysosome formation was inhibited. Moreover, suppression of AFD36229.1 expression prevented E. coli digestion and consequently led to the rupturing of A. castellanii. Our results demonstrated that the ACA1_077100, ACA1_175060, and AFD36229.1 genes of Acanthamoeba played crucial roles not only in the formation of phagosome and phagolysosome but also in the digestion of E. coli.

Phylogenomic, structural, and cell biological analyses reveal that Stenotrophomonas maltophilia replicates in acidified Rab7A-positive vacuoles of Acanthamoeba castellanii

“…2A ), is induced in A. castellanii trophozoites fed with E. coli DH5α ( 40 ). Interestingly, Kim et al ( 41 ) reported that silencing of ACA1-077100, which encodes XP_004335869.1 annotated as Rab1/RabD family small GTPase, disabled phagosome formation in A. castellanii fed with Escherichia coli . Currently, there are no reports on the downstream effectors recruited by Acanthamoeba Rabs for phagosome maturation and delivery to lysosomes.…”

“…The Rab repertoire of A. castellanii strain Neff was studied in the context of phylogenomic and evolutionary analyses, and it was estimated that it encodes 93 Rabs ( 38 , 39 )⁠. However, as detailed in the discussion, only two publications exist on the functional characterization of Acanthamoeba Rab GTPases ( 40 , 41 ).…”