SCAN: Formate metabolism in Desulfovibrio vulgaris Hildenborough

Abstract
Desulfovibrio vulgaris Hildenborough (DvH) is a model organism for the study of Sulfate-Reducing Bacteria (SRB). This group of anaerobic microorganisms is widespread in natural environments and also in gastrointestinal tract of animals, including humans. They are major contributors to the global carbon and sulfur cycles and play an important role in the bioremediation of contaminated soils. SRB use sulfate as terminal acceptor for the anaerobic oxidation of inorganic or organic substrates such as hydrogen, formate, lactate, or ethanol. The sulfate respiratory chain is still poorly understood and there seem to be several pathways involved in energy conservation such as cycling of hydrogen or CO. Electron transfer across the membrane is an important part of energy metabolism in SRB, and several membrane complexes and periplasmic proteins like hydrogenases and formate dehydrogenases are involved in the process. The DvH genome codes for three different formate dehydrogenases (Fdh). These metalloenzymes include a cofactor in their catalytic subunit that contains either molybdenum or tungsten.
In this work we investigated the role of the Fdhs in energy metabolism of DvH. The genes for the three Fdhs are very up-regulated during growth with hydrogen and sulfate, and the Fdh activity is very high compared to lactate-grown cells. Hydrogen is a major energy source for SRB in natural habitats, and growth on hydrogen induces major changes in the expression profile of energy-metabolism genes. The expression of each Fdh is dependent on the metal available during growth, as observed previously for the periplasmic hydrogenases. We purified the three Fdhs from different growth conditions and these show different catalytic properties.
The results show that when DvH grows with hydrogen as electron donor and sulfate as electron acceptor, formate has an important role in energy conservation by formate cycling providing an alternative pathway for energy generation. The redundancy in periplasmic enzymes enables the use of different metals, which may be crucial in sulfide-rich environments.

Short CV

1998 – 2003 – Degree in Microbial Biology and Genetics by Faculdade de Ciências, Universidade de Lisboa.

2002 – 2003 – Undergraduate training at Unidade de Tecnologia de Proteínas e Anticorpos Monoclonais, Instituto Nacional de Engenharia, Tecnologia e Inovação under the supervision of Dr. José Marcelino

2005 – Research student in the Microbial Biochemistry Lab (ITQB) under the supervision of Dra. Inês Pereira.

Since January 2006 – PhD fellowship by Fundação para a Ciência e Tecnologia at Microbial Biochemistry Lab (ITQB) under the supervision of Dra. Inês Pereira.