[S1-3] Identification of novel microbes using cocultivation with Acanthamoeba
We microbiologists are aware only a small fraction of microbes on the Earch. The limitation is simply due to the fact that we are not able to grow such microbes in laboratories. Our laboratory has been working on the molecular pathogenesis by intracellular bacteria Legionella infection. Acanthamoeba is a natural host of Legionella, therefore, we have decent expertise in the studies of intracellular microbes inside of Acanthamoeba. Taking advantage of the expertise, I conducted screening for novel symbiotic/parasitic microbes to Acanthamoeba facilitated by cocultivation. Of over 150 candidates, >80% microbes are either Proteobacteria or Bacteroidetes. In addition, NGS and phylogenetic analysis demonstrated that two bacteria represent a novel clade of the Phylum Actinobacteria Class Acidimicrobiia. The remaining <20% microbes are giant viruses, including Mimivirus/Megavirus/Moumouvirus (80%), one novel Pandoravirus, and five unknown giant viruses. NGS and phylogenetic analysis demonstrated that these unknown viruses represent a novel clade of Mimiviridae, which is distantly related to Mimiviruses known to infect Acanthamoeba and is rather closely related to Organic Lake phycodnavirus known to infect algae. These results illuminate that the world is full of microbes untouched by human hands, and the cocultivation-with-amoeba strategy helps us to reach where no one has gone before.