Golyshina, Olga V.

Abstract Manc.ar.chae'um. L. masc. adj. mancus , crippled, maimed; N.L. neut. n. archaeum , an archaeon; N.L. neut. n. Mancarchaeum , a crippled archaeon, an archaeon with absence of many pathways in the genome. Microcaldota / Microcaldia / Candidatus Micrarchaeales / Candidatus Micrarchaeaceae / Candidatus Mancarchaeum The archaeon Candidatus Mancarchaeum was identified in a binary culture during the isolation of Cuniculiplasma divulgatum strain PM4. The culture was established with water saturated sediment sample from acidic stream flowing on Parys Mountain copper mine, Isle of Anglesey, UK. The proportion of genomic reads of Ca . Mancarchaeum in the binary culture was ca. 10%. Ca . Mancarchaeum is phylogenetically affiliated with members of the phylum Microcaldota , class Microcaldia , order Ca . Micrarchaeales, family Ca . Micrarchaeaceae. The cultivation experiments and analysis of the 952,257 bp genome suggest aerobic/microaerobic, organoheterotrophic (proteolytic/peptidolytic), acidophilic, and mesophilic lifestyle. The genome analysis showed the lack of complete central pathways and limited respiratory capacities, indicating reliance on the host, in that particular case, C. divulgatum PM4. The metagenomic analysis also suggested the lateral gene transfer events between the Ca . Mancarchaeum and host in situ . Ca . Mancarchaeum was found as a minor member of microbial community of Parys Mountain acid mine drainage stream. Further environmental distribution of representatives of this Candidatus genus showed preferences to habitats with low pHs and temperatures between 35 and 50°C. DNA G + C content (mol%) : 39.5 (genome sequence). Type species : Candidatus Mancarchaeum acidiphilum Golyshina et al. 2017, CL1.

Significance We report on cultivation and characterization of an association between Candidatus Nanohalobium constans and its host, the chitinotrophic haloarchaeon Halomicrobium LC1Hm, obtained from a crystallizer pond of marine solar salterns. High-quality nanohaloarchael genome sequence in conjunction with electron- and fluorescence microscopy, growth analysis, and proteomic and metabolomic data revealed mutually beneficial interactions between two archaea, and allowed dissection of the mechanisms for these interactions. Owing to their ubiquity in hypersaline environments, Nanohaloarchaeota may play a role in carbon turnover and ecosystem functioning, yet insights into the nature of this have been lacking. Here, we provide evidence that nanohaloarchaea can expand the range of available substrates for the haloarchaeon, suggesting that the ectosymbiont increases the metabolic capacity of the host.