Korean J Parasitol.  2009 Dec;47(4):337-344. 10.3347/kjp.2009.47.4.337.

Endosymbionts of Acanthamoeba Isolated from Domestic Tap Water in Korea

  • 1Department of Parasitology, School of Medicine, Pusan National University, Busan, 602-739, Korea. hsyu@pusan.ac.kr
  • 2Department of Microbiology and Immunology, School of Medicine, Pusan National University, Busan, 602-739, Korea.
  • 3Department of Ophthalmology, School of Medicine, Pusan National University, Busan, 602-739, Korea.
  • 4Department of Nursing, College of Nursing, Pusan National University, Busan, 602-739, Korea.
  • 5Pusan National University Hospital Medical Research Institute, Busan 602-739, Korea.
  • 6Department of Parasitology, School of Medicine, Kyungpook National University, Daegu 700-422, Korea.


In a previous study, we reported our discovery of Acanthamoeba contamination in domestic tap water; in that study, we determined that some Acanthamoeba strains harbor endosymbiotic bacteria, via our molecular characterization by mitochondrial DNA restriction fragment length polymorphism (Mt DNA RFLP). Five (29.4%) among 17 Acanthamoeba isolates contained endosymbionts in their cytoplasm, as demonstrated via orcein staining. In order to estimate their pathogenicity, we conducted a genetic characterization of the endosymbionts in Acanthamoeba isolated from domestic tap water via 16S rDNA sequencing. The endosymbionts of Acanthamoeba sp. KA/WP3 and KA/WP4 evidenced the highest level of similarity, at 97% of the recently published 16S rDNA sequence of the bacterium, Candidatus Amoebophilus asiaticus. The endosymbionts of Acanthamoeba sp. KA/WP8 and KA/WP12 shared a 97% sequence similarity with each other, and were also highly similar to Candidatus Odyssella thessalonicensis, a member of the alpha-proteobacteria. The endosymbiont of Acanthamoeba sp. KA/WP9 exhibits a high degree of similarity (85-95%) with genus Methylophilus, which is not yet known to harbor any endosymbionts. This is the first report, to the best of our knowledge, to show that Methylophilus spp. can live in the cytoplasm of Acanthamoeba.


Acanthamoeba; endosymbiont; Methylophilus; Candidatus Amoebophilus asiaticus; Candidatus Odyssella thessalonicensis

MeSH Terms

Acanthamoeba/isolation & purification/*microbiology/ultrastructure
Alphaproteobacteria/classification/genetics/*isolation & purification
Bacteroidetes/classification/genetics/*isolation & purification
Cluster Analysis
DNA, Bacterial/chemistry/genetics
DNA, Ribosomal/chemistry/genetics
Fresh Water/*parasitology
Methylophilus/classification/genetics/*isolation & purification
Microscopy, Electron, Transmission
RNA, Ribosomal, 16S/genetics
Sequence Analysis, DNA
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