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Unexpected host dependency of Antarctic Nanohaloarchaeota


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Hamm, JN, Erdmann, S, Eloe-Fadrosh, EA, Angeloni, A, Zhong, L, Brownlee, C, Williams, TJ, Barton, K, Carswell, S, Smith, MA, Brazendale, S, Hancock, AM ORCID: 0000-0001-6049-5592, Allen, MA, Raftery, MJ and Cavicchioli, R 2019 , 'Unexpected host dependency of Antarctic Nanohaloarchaeota' , Proceedings of the National Academy of Sciences of the United States of America, vol. 116, no. 29 , pp. 14661-14670 , doi: 10.1073/pnas.1905179116.

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In hypersaline environments, Nanohaloarchaeota (Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, Nanohaloarchaeota [DPANN] superphylum) are thought to be free-living microorganisms. We report cultivation of 2 strains of Antarctic Nanohaloarchaeota and show that they require the haloarchaeon Halorubrum lacusprofundi for growth. By performing growth using enrichments and fluorescence-activated cell sorting, we demonstrated successful cultivation of Candidatus Nanohaloarchaeum antarcticus, purification of Ca. Nha. antarcticus away from other species, and growth and verification of Ca. Nha. antarcticus with Hrr. lacusprofundi; these findings are analogous to those required for fulfilling Koch’s postulates. We use fluorescent in situ hybridization and transmission electron microscopy to assess cell structures and interactions; metagenomics to characterize enrichment taxa, generate metagenome assembled genomes, and interrogate Antarctic communities; and proteomics to assess metabolic pathways and speculate about the roles of certain proteins. Metagenome analysis indicates the presence of a single species, which is endemic to Antarctic hypersaline systems that support the growth of haloarchaea. The presence of unusually large proteins predicted to function in attachment and invasion of hosts plus the absence of key biosynthetic pathways (e.g., lipids) in metagenome assembled genomes of globally distributed Nanohaloarchaeota indicate that all members of the lineage have evolved as symbionts. Our work expands the range of archaeal symbiotic lifestyles and provides a genetically tractable model system for advancing understanding of the factors controlling microbial symbiotic relationships.

Item Type: Article
Authors/Creators:Hamm, JN and Erdmann, S and Eloe-Fadrosh, EA and Angeloni, A and Zhong, L and Brownlee, C and Williams, TJ and Barton, K and Carswell, S and Smith, MA and Brazendale, S and Hancock, AM and Allen, MA and Raftery, MJ and Cavicchioli, R
Keywords: archaea, symbiont, DPANN
Journal or Publication Title: Proceedings of the National Academy of Sciences of the United States of America
Publisher: Natl Acad Sciences
ISSN: 0027-8424
DOI / ID Number: 10.1073/pnas.1905179116
Copyright Information:

Copyright © 2019 the Author(s). Published by PNAS.This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).

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