Definition for View source for Pyrobaculum aerophilum

Pyrobaculum aerophilum is a rod-shaped hyperthermophilic archaeum that was first isolated from boiling marine water in Maronti Beach, Ischia, Italy. Pyrobaculum aerophilum derives its name from the Greek noun "aer" (air) and the Greek adjective "philos" (loving). It was found that the archaeum grew optimally at 100°C and at pH 7.0. Both organic and inorganic compounds served as substrates during aerobic and anaerobic respiration. However, growth was inhibited by elemental sulfur. When discovered, Pyrobaculum aerophilum resembled members from the genera Thermoproteus and Pyrobaculum because of its ability to transform into spherical bodies, which resemble golf balls. After its 16S rRNA was sequenced, the new archaeum displayed traits more characteristic of the genus Pyrobaculum and was therefore classified as Pyrobaculum aerophilum. Most species in the genus Pyrobaculum cannot live in the presence of oxygen; however Pyrobaculum aerophilum can interestingly use oxygen for growth.

Pyrobaculum aerophilum cells were usually found to be 3 to 8 μm long and 0.6 μm wide. Very rarely, however, cells with a length of 20 μm appeared. Motility is achieved using monopolar flagellation with bundles of up to eight flagella. Each flagella averaged a diameter of 10 nm. Cells would transform into their terminal spherical phase mainly in the stationary-growth phase, at high nitrate concentrations, or pH values exceeding 8.0. Even in their terminal spherical phase, the cells can still enlarge or shrink depending on conditions. Colonies of Pyrobaculum aerophilum in their spherical phase exhibited greyish-yellow colonies with a harsh surface. Anaerobically conditioned cells in their normal rod-shaped phase exhibited a deep green color while aerobically grown cells in their normal rod-shaped phase exhibited a brownish yellow color.

Pyrobaculum aerophilum grew in media ranging from temperatures of 75 and 104°C. At the optimum temperature of growth, 100°C, the optimal doubling rate of the cells was observed to be 180 minutes. At the extreme temperature range of 75°C, the doubling rate of the cells dropped to a rate of approximiately 5 days. There was no difference in growth rate when the archaeum was cultured either in aerobic and anaerobic conditions. When living conditions were observed in different pH conditions, life was observed from a range of pH 5.8 to 9.0. The optimum rate of growth was observed at pH 7.0. However, when Pyrobaculum aerophilum was introduced in an environment exceeding pH 8.0, no growth was observed. Also, when the pH was lowered to 5.5 or exceeded 9.0, rapid cell lysis occurred. Different salt conditions were also observed for growth and life. Optimal salt conditions were observed at 1.5% NaCl. Also, growth of cells was observed when there were no traces of NaCl in the solution; however, once NaCl concentrations exceeded 3.6%, no growth was observed.