Guidelines for management of geoheritage: an approach in the Sertão Central, Brazilian Northeastern Semiarid

The characterisation of geoheritage and the understanding of the physical and socio-cultural features of a territory are essential to achieve the major geoconservation goals: protection and sustainable use of exceptional elements of geodiversity. This research was done in the Sertão Central, an economic vulnerable area in the hinterland of northeast Brazil, remarked by the Caatinga Biome and a rocky, semiarid landscape. The area comprises an assemblage of deformed igneous and meta- morphic rocks, such as gneisses, TTG rocks, schists, and granites. Starting from a regional geoheritage inventory done in 2015, fourteen geosites were selected and assessed, representing a wide regional tectonic evolution from the Precambrian West Gondwanan orogenesis to the Cenozoic development of particular examples of Brazilian granitic inselbergs. In addi- tion to the inventory of geosites, six geodiversity sites were also evaluated, along with five geocultural sites, highlighting the cultural value of geodiversity in the area. Based on the available information, an analysis with the main features and spatial configuration of the geoheritage was developed, allowing to designate the most appropriate use for each geological site. Considering geoconservation as a geoscientific fostering for the sustainable development, our study suggests a set of general guidelines for the management of geoheritage, in order to facilitate the decision-making process by local managers and stakeholders as well as to promote the discussion on geotourism strategies for the region. Organised according to well- defined geoconservation strategies, these guidelines could enhance the sustainable development of vulnerable regions, such as Sertão Central itself.The authors would like to thank an anonymous reviewer for the accurate and valuable comments on the original manuscript. In particular, PM is grateful to the Coordination for the Improvement of Higher Education Personnel (CAPES/Brazil) for her post doctorate scholarship (306365/2013-01/PNPD

METABOLISM OF SULFATE-REDUCING PROKARYOTES

Dissimilatory sulfate reduction is carried out by a heterogeneous group of bacteria and archaea that occur in environments with temperatures up to 105 degrees C. As a group together they have the capacity to metabolize a wide variety of compounds ranging from hydrogen via typical organic fermentation products to hexadecane, toluene, and several types of substituted aromatics. Without exception all sulfate reducers activate sulfate to APS; the natural electron donor(s) for the ensuing APS reductase reaction is not known. The same is true for the reduction of the product bisulfite; in addition there is still some uncertainty as to whether the pathway to sulfide is a direct six-electron reduction of bisulfite or whether it involves trithionate and thiosulfate as intermediates. The study of the degradation pathways of organic substrates by sulfate-reducing prokaryotes has led to the discovery of novel non-cyclic pathways for the oxidation of the acetyl moiety of acetyl-CoA to CO2. The most detailed knowledge is available on the metabolism of Desulfovibrio strains, both on the pathways and enzymes involved in substrate degradation and on electron transfer components and terminal reductases. Problems encountered in elucidating the flow of reducing equivalents and energy transduction are the cytoplasmic localization of the terminal reductases and uncertainties about the electron donors for the reactions catalyzed by these enzymes. New developments in the study of the metabolism of sulfate-reducing bacteria and archaea are reviewed