Unravelling the one‐carbon metabolism of the acetogen Sporomusa strain An4 by genome and proteome analysis

Abstract

The Sporomusa genus comprises anaerobic spore-forming acetogenic bacteria that stain Gram-negative. Sporomusa species typically grow with one-carbon substrates and N-methylated compounds. In the degradation of these compounds methyltransferases are involved. In addition, Sporomusa species can grow autotrophically with H2 and CO2 , and use a variety of sugars for acetogenic growth. Here we describe a genome analysis of Sporomusa strain An4 and a proteome analysis of cells grown under five different conditions. Comparison of the genomes of Sporomusa strain An4 and Sporomusa ovata strain H1 indicated that An4 is a S. ovata strain. Proteome analysis showed a high abundance of several methyltransferases, predominantly trimethylamine methyltransferases, during growth with betaine, whereas trimethylamine is one of the main end-products of betaine degradation. In methanol degradation methyltransferases are also involved. In methanol-utilizing methanogens, two methyltransferases catalyse methanol conversion, methyltransferase 1 composed of subunits MtaB and MtaC and methyltransferase 2, also called MtaA. The two methyltransferase 1 subunits MtaB and MtaC were highly abundant when strain An4 was grown with methanol. However, instead of MtaA a methyltetrahydrofolate methyltransferase was synthesized. We propose a novel methanol degradation pathway in Sporomusa strain An4 that uses a methyltetrahydrofolate methyltransferase instead of MtaA.

Glycine betaine metabolism in the acetogenic bacterium Acetobacterium woodii

“…Visser et al . identified these proteins of strain An4 in a proteomic approach and proposed a metabolic model in which the methyl group of GB is not directly transferred to THF but GB is reduced to TMA first (Visser et al ., ). Although an additional demethylation of GB was not ruled out, the fate of the resulting methyl group was not determined.…”

Methanol metabolism in the acetogenic bacterium Acetobacterium woodii

“…Therefore Awo_c22760‐Awo_c22740 most likely encode the methanol methyltransferase system of A. woodii . As it was already recognized for M. thermoacetica and S. ovata strain An4 the MTII of A. woodii shares no similarity to a methyl‐CoP:CoM methyltransferase (MTII) known to be involved in the methanol metabolism of methanogens (Das et al ., ; Visser et al ., ), but this is not too surprising since the acceptor molecules CoM and THF are quite different. Based on the high homology to the methanol utilization clusters of other acetogenic bacteria and methanogenic archaea, the gene cluster Awo_c22810‐c22740 is further named mta cluster of A. woodii .…”

“…Moorella thermoacetica lacks the biosynthesis genes. In addition the order of the genes encoding MTI, MTII and CoP is different in S. ovata and M. thermoacetica (Das et al ., ; Pierce et al ., ; Visser et al ., ). These data implicate that these gene clusters encode the methanol‐specific methyltransferases of A. dehalogenans , E. limosum , S. ovata and M. thermoacetica .…”

Energetics and Application of Heterotrophy in Acetogenic Bacteria

“…In addition, the WLP is perfectly suited to metabolize C 1 compounds, such as methanol, formate, or CO (44). Some acetogens, such as different Sporomusa species, seem to be specialized for the utilization of C-1 groups from methylated compounds, such as betaine, sarcosine or N,N-dimethylglycine, or can even utilize abiotic electron sources such as Fe(0) (47,48).…”