Nanobdella aerobiophila gen. nov., sp. nov., a thermoacidophilic, obligate ectosymbiotic archaeon, and proposal of Nanobdellaceae fam. nov., Nanobdellales ord. nov. and Nanobdellia class. nov.
Shingo Kato, Ayaka Ogasawara, Takashi Itoh, Hiroyuki D. Sakai, Michiru Shimizu, Masahiro Yuki, Masanori Kaneko, Tomonori Takashina, Moriya Ohkuma
Abstract
A co-culture of a novel thermoacidophilic, obligate symbiotic archaeon, designated as strain MJ1 T , with its specific host archaeon Metallosphaera sedula strain MJ1HA was obtained from a terrestrial hot spring in Japan. Strain MJ1 T grew in the co-culture under aerobic conditions. Coccoid cells of strain MJ1 T 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 MJ1 T 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 MJ1 T cells concentrated from the co-culture. Strain MJ1 T 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 MJ1 T 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 MJ1 T (=JCM 33616 T =DSM 111728 T ). In addition, we propose the names Nanobdellaceae fam. nov., Nanobdellales ord. nov., and Nanobdellia class. nov. to accommodate the novel genus.