Novel pentose degradation pathways in archaea
D-Xylose and L-arabinose, major components of the abundant hemicellulose, are degraded in most bacteria to xylose-5-phosphate as an intermediate. In contrast we have shown, that halophilic archaea, e. g. Haloferax volcanii, degrade these two pentoses via novel oxidative pathways. The studies included (I) genome analyses, (II) transcriptional analyses, (III) construction and analyses of knock-out mutants and (IV) expression and characterization of enzymes involved. Further, we have identified a novel transcriptional regulator, XacR, that belongs to the IclR family of bacterial regulators. XacR was characterized as an activator of D-xylose/L-arabinose degrading genes and as a repressor of its own synthesis. XacR homologues were found only in haloarchaea but are absent in any other archaeal genome. Since XacR homologues were also absent in the eukaryal domain, but are highly abundant in bacteria, it can be concluded that the haloarchaeal XacR originated from IclR from bacteria via lateral gene transfer. Pentose degradation pathways were also characterized in the thermoacidophilic archaea Sulfolobus solfataricus and S. acidocaldarius. In these archaea D-xylose/L-arabinose are degraded by a variant of the oxidative pathways described in haloarchaea. (funded by the DFG).
Johnsen et al. (2015) XacR – a novel transcriptional regulator of D-xylose and L-arabinose catabolism in the haloarchaeon Haloferax volcanii. Environ Microbiol 17:1663-1676
Nunn et al. (2010) Metabolism of pentose sugars in the hyerthermophilic archaea Sulfolobus solfataricus and Sulfolobus acidocaldarius. J Biol Chem 285:33701-9
Johnsen et al. (2009) D-Xylose degradation pathway in the halophilic archaeon Haloferax volcanii. J Biol Chem 284:27290-303