Nanobdella aerobiophila gen. nov., sp. nov., a thermoacidophilic, obligate ectosymbiotic archaeon, and proposal of Nanobdellaceae fam. nov., Nanobdellales ord. nov. and Nanobdellia class. nov.

Abstract

A co-culture of a novel thermoacidophilic, obligate symbiotic archaeon, designated as strain MJ1T, with its specific host archaeon Metallosphaera sedula strain MJ1HA was obtained from a terrestrial hot spring in Japan. Strain MJ1T grew in the co-culture under aerobic conditions. Coccoid cells of strain MJ1T were 200–500 nm in diameter, and attached to the MJ1HA cells in the co-culture. The ranges and optima of the growth temperature and pH of strain MJ1T in the co-culture were 60–75 °C (optimum, 65–70 °C) and pH 1.0–4.0 (optimum, pH 2.5), respectively. Core lipids of dialkyl glycerol tetraethers (GDGT)−3 and GDGT-4 were highly abundant in MJ1T cells concentrated from the co-culture. Strain MJ1T has a small genome (0.67 Mbp) lacking genes for biosynthesis of essential biomolecules, such as nucleotides, lipids and ATP. The genomic DNA G+C content was 24.9 mol%. The 16S rRNA gene sequence of strain MJ1T was most closely related to that of the cultivated species, ‘Nanopusillus acidilobi’ strain N7A (85.8 % similarity). Based on phylogenetic and physiological characteristics, we propose the name Nanobdella aerobiophila gen. nov., sp. nov. to accommodate the strain MJ1T (=JCM 33616T=DSM 111728T). In addition, we propose the names Nanobdellaceae fam. nov., Nanobdellales ord. nov., and Nanobdellia class. nov. to accommodate the novel genus.

Valid publication of four additional phylum names

“…The description of the type and sole genus of the order, Nanobdella Kato et al 2022 [33, 34], agrees with ‘ Nanoarchaeota ’ Huber et al 2002 [32] in that it comprises tiny cocci living in obligate symbiosis, attached to the surface of cells of a host archaeon. Nanobdella Kato et al 2022 [33, 34] is a validly published name. The type strain of its type species has been deposited in two culture collections, growing in co-culture with its host.…”

“…2022, has been taxonomically assigned by Kato et al [33] to the phylum ‘ Nanoarchaeota ’ Huber et al [32]. The description of the type and sole genus of the order, Nanobdella Kato et al 2022 [33, 34], agrees with ‘ Nanoarchaeota ’ Huber et al 2002 [32] in that it comprises tiny cocci living in obligate symbiosis, attached to the surface of cells of a host archaeon. Nanobdella Kato et al 2022 [33, 34] is a validly published name.…”

“…The description of the phylum is as given for ‘ Nanoarchaeota ’ by Huber et al [32] but also encompassing the class Nanobdellia Kato et al 2022 [33, 34]. Usually tiny cocci, attached to the surface of the cells of an archaeal host.…”

“…Usually tiny cocci, attached to the surface of the cells of an archaeal host. The nomenclatural type is the genus Nanobdella Kato et al 2022 [33, 34].…”

“…The class Nanobdellia Kato et al 2022 [33,34], including its type order Nanobdellales Kato et al 2022, has been taxonomically assigned by Kato et al [33] to the phylum 'Nanoarchaeota' Huber et al [32]. The description of the type and sole genus of the order, Nanobdella Kato et al 2022 [33,34], agrees with 'Nanoarchaeota ' Huber et al 2002 [32] in that it comprises tiny cocci living in obligate symbiosis, attached to the surface of cells of a host archaeon. Nanobdella Kato et al 2022 [33,34] is a validly published name.…”