Identification and ultrastructural characterization of Acanthamoeba bacterial endocytobionts belonging to the Alphaproteobacteria class

PLoS One. 2018 Oct 24;13(10):e0204732. doi: 10.1371/journal.pone.0204732. eCollection 2018.

Abstract

The detection and identification of two endocytobiotic bacterial strains, one affiliated to the "Candidatus Caedibacter acanthamoebae"/"Ca. Paracaedimonas acanthamoeba", and another to the endosymbiont of Acanthamoeba UWC8 and "Ca. Jidaibacter acanthamoeba" are described. For endocytobiont screening, we developed a PCR method with a set of broad-range bacterial 16S rRNA primers to substitute the commonly used but technically demanding fluorescent in situ hybridization technique. Our PCR test alone without sequencing failed to discriminate the endocytobiont-containing and endocytobiont-free Acanthamoeba sp. due to the presence of mismatched primers to host mitochondrial DNA. We highlighted the need to perform bacterial primer checking against the Acanthamoeba genome to avoid false positive detection in PCR. Although the genetic aspect of "Ca. Caedibacter acanthamoebae"/"Ca. Paracaedimonas acanthamoeba" and the endosymbiont of Acanthamoeba UWC8/"Ca. Jidaibacter acanthamoeba" are well studied, knowledge pertaining to their morphologies are quite vague. Hence, we used transmission electron microscopy to examine our endocytobionts which are affiliated to previously described intracellular bacteria of Acanthamoeba sp. We used good-quality TEM images for the localization and the fate of the current endocytobionts inside different life stages of the hosts. Furthermore, to the best of our knowledge, our TEM findings are the first to provide morphological evidence for the clearance of defective Acanthamoeba endocytobionts via an autophagic-like process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acanthamoeba / genetics*
  • Alphaproteobacteria / genetics*
  • DNA, Bacterial / genetics
  • DNA, Mitochondrial / genetics
  • Genome, Bacterial / genetics
  • Host-Pathogen Interactions / genetics
  • Microscopy, Electron, Transmission / methods
  • RNA, Ribosomal, 16S / genetics

Substances

  • DNA, Bacterial
  • DNA, Mitochondrial
  • RNA, Ribosomal, 16S

Grants and funding

The research grant was awarded by the International Medical University under the grant number BMS I01(06). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.