Vitamin B12 Auxotrophy in Isolates from the Deep Subsurface of the Iberian Pyrite Belt

Vitamin B-12 is an enzymatic cofactor that is essential for both eukaryotes and prokaryotes. The development of life in extreme environments depends on cofactors such as vitamin B-12 as well. The genomes of twelve microorganisms isolated from the deep subsurface of the Iberian Pyrite Belt have been analyzed in search of enzymatic activities that require vitamin B-12 or are involved in its synthesis and import. Results have revealed that vitamin B-12 is needed by these microorganisms for several essential enzymes such as ribonucleotide reductase, methionine synthase and epoxyqueosine reductase. Isolate Desulfosporosinus sp. DEEP is the only analyzed genome that holds a set core of proteins that could lead to the production of vitamin B-12. The rest are dependent on obtaining it from the subsurface oligotrophic environment in which they grow. Sought proteins involved in the import of vitamin B-12 are not widespread in the sample. The dependence found in the genomes of these microorganisms is supported by the production of vitamin B-12 by microorganisms such as Desulfosporosinus sp. DEEP, showing that the operation of deep subsurface biogeochemical cycles is dependent on cofactors such as vitamin B-12.

Automated summary

Vitamin B-12 is essential for enzymatic activities in both eukaryotes and prokaryotes, including microorganisms in extreme environments. Analysis of genomes from microorganisms in the deep subsurface of the Iberian Pyrite Belt reveals their dependence on vitamin B-12 for important enzymes. Only one isolate, Desulfosporosinus sp. DEEP, has the genetic capability to produce vitamin B-12, while others rely on obtaining it from the oligotrophic environment they grow in. Import proteins for vitamin B-12 are not widely present in the samples. This dependence is supported by the production of vitamin B-12 by Desulfosporosinus sp. DEEP, indicating the significance of cofactors like vitamin B-12 in deep subsurface biogeochemical cycles.