Points

• Achieved the first successful isolation of ultrasmall bacteria parasitic to methanogenic archaea in the world
• Observed a unique parasitic interaction between the isolate and its host methanogenic archaea
• We proposed Minisyncoccus archaeiphilus PMX.108T gen. nov., sp.nov. and the associated family, order, class, and phylum as Minisyncoccaceae fam. nov. Minisyncoccales nov., Minisyncoccia class. nov. and Minisyncoccota phyl. nov., respectively.

Summary

AIST researchers, in collaboration with JAMSTEC, Hokkaido University and Tohoku University, have succeeded in cultivating an ultrasmall bacterial strain parasitizing methanogenic archaea and classified the strain PMX.108T as new species and genus of Minisyncoccus archaeiphilus.
We have discovered, for the first time in the world, bacteria that parasitize the methanogenic archaea, which play a central role in anaerobic wastewater treatment systems. The ultrasmall bacterium inhibits the growth of the host methanogenic archaeon Methanospirillum hungatei. This study represents the first successful cultivation of ultrasmall bacteria that parasitize Archaea, which evolutionarily diverged approximately 4 billion years ago and exhibit significant biological differences in cell membrane lipids, genetic information, and other biochemical characteristics. The bacterium was observed to have limited host range and to attach only host archaeon-specific sites.
Furthermore, we have proposed a new phylum Minisyncoccota formerly known as "Candidate phyla radiation (CPR)”. The phylogenetically classification and deposition of the CPR bacterium to a public culture collections will advance research on the CPR bacteria, and is expected to advance our understanding of the physiology and ecological role of the bacteria, which have remained a mystery until now.

Background

Candidate phyla radiation, a large bacterial phylogenetic group that includes various uncultivated lineages, are ubiquitous in natural and artificial environments, but their ecophysiology in ecosystems remains largely unknown due to the difficulty of cultivating them. The CPR bacteria have been predicted to adopt a parasitic or predatory lifestyles on the host organisms because of their small cell and genome size and lack of biosynthetic pathways for their growth. Although some CPR bacteria that demonstrate intra-domain interactions have been successfully cultured, there are no cases where cultured strains have been made publicly available through culture collections, which is hindering the progress in the research field.

Paper Information

Researchers

Kyohei Kuroda, Senior Researcher
Takashi Narihiro, Group Leader
Ryosuke Nakai, Senior Researcher
Takashi Narihiro, Group Leader
Ryosuke Nakai, Senior Researcher

Microbial Ecology and Technology Research Group, Department of Life Science and Biotechnology, Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)

Yuga Hirakata, AIST Postdoctoral Researcher

Microbial and Genetic Resources Research Group, Department of Life Science and Biotechnology, Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)

Meri Nakajima, doctoral student

Hokkaido University, Graduate School of Engineering

Hisashi Satoh, Professor

Hokkaido University, Faculty of Engineering

Kengo Kubota Associate Professor

Tohoku University, Graduate School of Environmental Studies

Masaru K. Nobu, Senior researcher

Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star)

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