Metallosphaera cuprina sp. nov., an acidothermophilic, metal-mobilizing archaeon.

A novel acidothermophilic archaeon, strain Ar-4(T), was isolated from a sulfuric hot spring in Tengchong, Yunnan, China. Cells of strain Ar-4(T) were Gram-staining-negative, irregular cocci and motile by means of flagella. Strain Ar-4(T) grew over a temperature range of 55-75 °C (optimum, 65 °C), a pH range of 2.5-5.5 (optimum, pH 3.5) and a NaCl concentration range of 0-1 % (w/v). The novel strain was aerobic and facultatively chemolithoautotrophic. The strain could extract metal ions from sulfidic ore. It was also able to oxidize reduced sulfur compounds. In addition, it was able to use heterogeneous organic materials for organotrophic growth. The main cellular lipids were calditoglycerocaldarchaeol (CGTE) and caldarchaeol (DGTE). The DNA G+C content of the strain was 40.2 mol%. Analysis of 16S rRNA gene sequences showed that strain Ar-4(T) was phylogenetically related to members of the genus Metallosphaera and had sequence similarities of 97.7 %, 97.0 % and 96.8 % with Metallosphaera hakonensis DSM 7519(T), Metallosphaera sedula DSM 5348(T) and Metallosphaera prunae DSM 10039(T), respectively. Strain Ar-4(T) showed DNA-DNA relatedness values of 47.5 %, 30.8 % and 29.1 % with M. hakonensis DSM 7519(T), M. sedula DSM 5348(T) and M. prunae DSM 10039(T), respectively. The differences in cell motility, the temperature and pH ranges for growth, the ability to utilize carbon sources, the DNA G+C content, and the low DNA-DNA relatedness values distinguished strain Ar-4(T) from recognized species of the genus Metallosphaera. On the basis of these results, it was concluded that strain Ar-4(T) represents a novel species of the genus Metallosphaera, for which the name Metallosphaera cuprina is proposed. The type strain is Ar-4(T) ( = JCM 15769(T) = CGMCC 1.7082(T)).