Natranaerobius thermophilus: an anaerobic, polyextremophilic microorganism with unique properties and adaptive mechanisms.

Abstract

Natranaerobius thermophilus is an obligately anaerobic, halophilic alkalithermophilic microorganism that was isolated from the sediment of Lake Fazda of the Wadi An Natrun, Egypt. It can grow optimally at 3.3-3.9 M Na⁺, 53℃ and pH 9.5 (measured at 55℃). N. thermophilus has several properties that distinguish it from other halophilic anaerobes; it is simultaneously adapted to alkaline pH and high temperature and adopts a combined salt-in-compatible solute strategy for osmoadaptation, accumulating glycine betaine, proline and potassium in its cytoplasm. The F₁F₀-ATPase of N. thermophilus is Na⁺-coupled and functions primarily as a Na⁺ pump, expelling Na⁺ from the cytoplasm at the expense of ATP. N. thermophilus has a large cohort of electrogenic Na⁺(K⁺)/ H⁺ antiporters for cytoplasm acidification and has an acidic proteome. This minireview discusses the phylogeny and metabolism of N. thermophilus. Adaptive mechanisms employed by N. thermophilus to combat multiple extreme growth conditions will be presented.