Substrate-Dependent Regulation of Carbon Catabolism in Marine Sulfate-Reducing <i>Desulfobacterium autotrophicum</i> HRM2

Abstract

Desulfobacterium autotrophicum HRM2 is a metabolically versatile sulfate-reducing bacterium, capable of heterotrophic (e.g. with organic acids and alcohols) and chemolithoautotrophic growth (with H₂/CO₂). It employs the Wood-Ljungdahl pathway for complete oxidation of acetyl-CoA to CO₂ and for CO₂ fixation. Here, we investigated substrate-dependent regulation at different levels of anaerobic carbon catabolism in this bacterium. (a) Whole-cell adaptation studies indicated an inducibleutilization of short-chained alcohols, agreeing with a substrate-specific abundance increase (up to 40-fold) of alcohol dehydrogenase Adh4. Simultaneous utilization of lactate and 1-propanol was paralleled by adh4 expression and Adh4 formation, respectively. (b) Degradation of propionate generally involves methylmalonyl-CoA mutase (Sbm). Expression of sbm was upregulated during growth with 1-propanol, but not with a mixture of lactate and 1-propanol. Correspondingly, propionate was excreted during growth with this substrate mixture. (c) CO dehydrogenase, the key enzyme of the Wood-Ljungdahl pathway, is encoded by several genes (cdhC, cdh1 and cdh2) located at different genomic positions. Expression of all of these genes during heterotrophic and autotrophic growth points to a reversible operation of the Wood-Ljungdahl pathway. In summary, the different regulatory patterns displayed by Db. autotrophicum HRM2 at the tested metabolic levels point to a multi-layered regulatory network.

Genome and catabolic subproteomes of the marine, nutritionally versatile, sulfate-reducing bacterium Desulfococcus multivorans DSM 2059

“…Except for formate dehydrogenase (FdhH, solely genome-encoded Fdh) all other protein constituents of the pathway were identified across all tested 17 substrate adaptation conditions, pointing to a constitutive formation. This agrees with proteogenomic data available for D. autotrophicum HRM2 [14, 17, 18] and D. toluolica Tol2 [15]. …”

“…The first members of the Desulfobacteraceae to have their genomes sequenced are facultatively chemolithoautotrophic Desulfobacterium autotrophicum HRM2 [14], aromatic compound degradation specialist Desulfobacula toluolica Tol2 [15] and the two n -alkane degraders Desulfococcus oleovorans Hxd3 (unpublished) and Desulfatibacillum alkenivorans AK-01 [16]. Studies on the differential proteomic level have been performed with D. autotrophicum HRM2 [17, 18] and D. toluolica Tol2 [15]. …”

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

“…Modifications of this pathway in A. fulgidus mainly include different electron acceptors (Thauer, M€ oller-Zinkhan, & Spormann, 1989). The genomes of completely oxidizing SRP (see Section 7.1.2) allowed deciphering the common genetic basis of the Wood-Ljungdahl pathway, and targeted gene expression analysis with D. autotrophicum HRM2 confirmed reversibility of the pathway under heterotrophic and autotrophic growth conditions, respectively (Amann, Lange, Schuler, & Rabus, 2010). Overall, acetate utilization, viz., CO dehydrogenase activity, belongs to the metabolic hallmarks of most completely oxidizing SRP.…”

Metagenomics in CO2 Monitoring

“…3). Candidatus Nitrospira defluvii uses the rTCA pathway, while the deltaproteobacterial taxa (D. autotrophicum HRM2, D. alkenivorans AK-01, and uncultured Desulfobacterium) and Candidatus Kuenina stuttgartiensis utilizes the WL-pathway [9, [21][22][23][24][25]. Finally the archaeon N. maritimus likely makes use of a variant of the 3HP/4HB-pathway [26].…”