Physiological versatility of the extremely thermoacidophilic archaeon Metallosphaera sedula supported by transcriptomic analysis of heterotrophic, autotrophic, and mixotrophic growth

Abstract

Comparative transcriptomic analysis of autotrophic, heterotrophic, and mixotrophic growth of the archaeon Metallosphaera sedula (70 degrees C, pH 2.0) revealed candidates for yet-to-be-confirmed components of the 3-hydroxypropionate/4-hydroxybutyrate pathway and implicated a membrane-bound hydrogenase (Msed_0944-Msed_0946) for growth on H(2). Routes for generation of ATP and reducing equivalents were also identified.

FIG. 1.

Growth curves for the third passage of heterotrophic (•), autotrophic (▪), and mixotrophic (▴) growth cultures of M. sedula. Biological repeats are represented by open symbols and broken lines. Error bars represent σ.

FIG. 2.

Transcriptional levels of M. sedula ORFs implicated in the 3-hydroxypropionate/4-hydroxbutyrate cycle (based on the M. sedula model proposed in reference 4) during heterotrophic (H₁ and H₂), autotrophic (A₁ and A₂), and mixotrophic (M₁ and M₂) growth. Heat plots were constructed using AFM 4.0 (5). Red indicates high transcription, and green indicates low transcription; corresponding numbers represent least-squares means of normalized log₂-transformed transcription levels relative to the overall average transcription level of 0. Enzymes: 1 = acetyl-CoA/propionyl-CoA carboxylase, 2 = malonyl-CoA/succinyl-CoA reductase, 3 = malonic semialdehyde reductase, 4 = 3-hydroxypropionyl-CoA synthetase, 5 = 3-hydroxypropionyl-CoA dehydratase, 6 = acryloyl-CoA reductase, 7 = methylmalonyl-CoA epimerase, 8 = methylmalonyl-CoA mutase, 9 = succinate semialdehyde reductase, 10 = 4-hydroxybutyryl-CoA synthetase, 11 = 4-hydroxybutyryl-CoA dehydratase, 12 = crotonyl-CoA hydratase, 13 = (S)-3-hydroxybutyryl-CoA dehydrogenase, 14 = acetoacetyl-CoA β-ketothiolase.

FIG. 3.

Transcriptional levels of M. sedula hydrogenase-associated ORFs during heterotrophic (H₁ and H₂), autotrophic (A₁ and A₂), and mixotrophic (M₁ and M₂) growth. Heat plots were constructed using AFM 4.0 (5). Red indicates high transcription, green indicates low transcription, and corresponding numbers represent least-squares means of normalized log₂-transformed transcription levels relative to the overall average transcription level of 0.