PYROBACULUM-AEROPHILUM SP-NOV, A NOVEL NITRATE-REDUCING HYPERTHERMOPHILIC ARCHAEUM

A novel rod-shaped hyperthermophilic archaeum has been isolated from a boiling marine water hole at Maronti Beach, Ischia, Italy. It grew op timally at 100-degrees-C and pH 7.0 by aerobic respiration as well as by dissimilatory nitrate reduction, forming dinitrogen as a final prod uct. Organic and inorganic compounds served as substrates during aerob ic and anaerobic respiration. Growth was inhibited by elemental sulfur . The cell wall was composed of a surface layer of hexameric protein c omplexes arranged on a p6 lattice. The core lipids consisted mainly of glycerol diphytanyl glycerol tetraethers with various degrees of cycl ization. The G+C content was 52 mol%. The new isolate resembled member s of the genera Thermoproteus and Pyrobaculum by its ability to form c haracteristic terminal spherical bodies (''golf clubs''). On the basis of its 16S rRNA sequence, the new isolate exhibited a close relations hip to the genus Pyrobaculum. It is described as a new species, which we name Pyrobaculum aerophilum (type strain: IM2; DSM 7523).