Respiratory quinones in Archaea: phylogenetic distribution and application as biomarkers in the marine environment.

The distribution of respiratory quinone electron carriers among cultivated organisms provides clues on both the taxonomy of their producers and the redox processes these are mediating. Our study of the quinone inventories of 25 archaeal species belonging to the phyla E ury-, C ren- and T haumarchaeota facilitates their use as chemotaxonomic markers for ecologically important archaeal clades. Saturated and monounsaturated menaquinones with six isoprenoid units forming the alkyl chain may serve as chemotaxonomic markers for T haumarchaeota. Other diagnostic biomarkers are thiophene-bearing quinones for S ulfolobales and methanophenazines as functional quinone analogues of the M ethanosarcinales. The ubiquity of saturated menaquinones in the A rchaea in comparison to B acteria suggests that these compounds may represent an ancestral and diagnostic feature of the A rchaea. Overlap between quinone compositions of distinct thermophilic and halophilic archaea and bacteria may indicate lateral gene transfer. The biomarker potential of thaumarchaeal quinones was exemplarily demonstrated on a water column profile of the Black Sea. Both, thaumarchaeal quinones and membrane lipids showed similar distributions with maxima at the chemocline. Quinone distributions indicate that T haumarchaeota dominate respiratory activity at a narrow interval in the chemocline, while they contribute only 9% to the microbial biomass at this depth, as determined by membrane lipid analysis. [ABSTRACT FROM AUTHOR]