Abstract
A strictly anaerobic, dissimilatory Fe(III)-reducing hyperthermophilic
archaeon, designated as strain IOH1T, was isolated
from a new deep-sea hydrothermal vent (Onnuri Vent Field)
area in the Central Indian Ocean ridge. Strain IOH1T showed
> 99% 16S rRNA gene sequence similarity with Thermococcus
celericrescens TS2T (99.4%) and T. siculi DSM 12349T (99.2%).
Additional three species T. barossii SHCK-94T (99.0%), T. celer
Vu13T (98.8%), and T. piezophilus (98.6%) showed > 98.6%
of 16S rRNA gene sequence similarity, however, the maximum
OrthoANI value is 89.8% for the genome of T. celericrescens
TS2T. Strain IOH1T cells are coccoid, 1.2–1.8 μm
in diameter, and motile by flagella. Growth was at 70–82°C
(optimum 80°C), pH 5.4–8.0 (optimum pH 6.0) with 2–4%
(optimum 3%) NaCl. Growth of strain IOH1T was enhanced
by starch, pyruvate, D(+)-maltose and maltodextrin as a carbon
sources, and elemental sulfur as an electron acceptor;
clearly different from those of related species T. celecrescens
DSM 17994T and T. siculi DSM 12349T. Strain IOH1T, T. celercrescence
DSM 17994T, and T. siculi DSM 12349T reduced
soluble Fe(III)-citrate present in the medium, whereas the
amount of total cellular proteins increased with the concomitant
accumulation of Fe(II). We determined a circular chromosome
of 2,234 kb with an extra-chromosomal archaeal
plasmid, pTI1, of 7.7 kb and predicted 2,425 genes. The DNA
G + C content was 54.9 mol%. Based on physiological properties,
phylogenetic, and genome analysis, we proposed that
strain IOH1T (= KCTC 15844T = JCM 39077T) is assigned to
a new species in the genus Thermococcus and named Thermococcus
indicus sp. nov.
Citations
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