Job, Daniel

2013, Joseph, Edith, Letardi, Paola, Junier, Pilar, Simon, Anaele, Comensoli, Lucrezia, Job, Daniel, Wörle, Marie

We propose an innovative treatment by which the protection of copper-based artefacts can be provided by naturally occurring microorganisms. The properties of some fungi were exploited for the transformation of existing corrosion patinas into copper oxalates. The latter are known to be insoluble and chemically stable. Within the earlier EU-ARTECH and BAHAMAS projects, very promising results were obtained with an almost 100% conversion from copper hydroxysulfates and hydroxychlorides into copper oxalates. A fungal strain was used which had been isolated from vineyard soil heavily contaminated with copper. Further scientific investigations were carried out to determine the parameters of the process and allowing the formation of a reproducible and homogeneous patina of copper oxalates, called biopatina to highlight its biological origin. Particular attention was paid to the efficacy, durability and impact on colour of the newly developed treatment. Different copper and bronze coupons with either urban or marine patinas were prepared. Several analytical techniques were used for the characterisation of the patinas: Fourier Transform InfraRed microspectroscopy (µFTIR), colourimetry and Electrochemical Impedance Spectroscopy (EIS). The coupons were treated with either the biological treatment or reference materials (wax: Cosmoloid H80; silane: Dynasylan® F8263) and exposed to atmospheric corrosion (ISMAR-SMS Genoa Harbour, corrosivity class 5) in December 2011. The long-term behaviour and performance of the treatments under study was monitored and compared over a one year period using the same complement of analytical techniques used for the characterisation of the original patinas. These first measurements suggested a different weathering behaviour of the biopatina. In fact, in comparison to the silane and wax treatments the biopatina showed a lower colour variation, and a corrosion stabilisation process seemed to be in progress. A deeper analysis of colour and corrosion rate variation from different application methods was also achieved. The complete assessment of the different treatments will be finished this year.

2011-6-15, Job, Daniel

2010, Job, Daniel

2008, Kuffer, Nicolas, Gillet, François, Senn-Irlet, Béatrice, Aragno, Michel, Job, Daniel

The fine-scale ecological determinants for wood-inhabiting aphyllophoroid basidiomycetes were investigated with statistical analyses of the occurrence of fruit bodies on woody debris collected in Switzerland and Ukraine. Three substrate descriptors were considered: diameter, degree of decomposition to those local environmental descriptors were detected. Three classes for diameter, as well as for degree of decomposition were thus delimited. They revealed the importance of very small sizes, which were not reported in the literature so far: the relevant diameter class limits were about 0.72 cm and 1.35 cm. Within the host tree species, a clear distinction between coniferous and broadleaf species was found. The next splits followed rather climatic determinants of tree distribution than taxonomical entities such as families or genera. The fidelity of the 59 fungal species to diameter classes, decomposition classes and host tree species was measured by the Dufrene-Legendre index and only significant responses after permutation tests were retained. This brought new insights on the ecology of many wood-inhabiting aphyllophoroid basidiomycetes. Redundancy Analysis was applied to investigate the response of fungal species to diameter and degree of decompostion of woody debris from the most common host tree species, Fagus sylvatica. This direct gradient analysis made it possible to reconstruct the succession of fungal species along the wood decomposition process.

2011-10-21, Job, Daniel

2010-6-15, Job, Daniel

2009-6-15, Job, Daniel

2011-10-10, Job, Daniel

2010-6-15, Job, Daniel

2009, Khammar, Nadia, Martin, Gaëtan, Ferro, Katia, Job, Daniel, Aragno, Michel, Verrecchia, Eric

Oxalate catabolism, which can have both medical and environmental implications, is performed by phylogenetically diverse bacteria. The formyl-CoA-transferase gene was chosen as a molecular marker of the oxalotrophic function. Degenerated primers were deduced from an alignment of frc gene sequences available in databases. The specificity of primers was tested on a variety of frc-containing and frc-lacking bacteria. The frc-primers were then used to develop PCR-DGGE and real-time SybrGreen PCR assays in soils containing various amounts of oxalate. Some PCR products from pure cultures and from soil samples were cloned and sequenced. Data were used to generate a phylogenetic tree showing that environmental PCR products belonged to the target physiological group. The extent of diversity visualised on DGGE pattern was higher for soil samples containing carbonate resulting from oxalate catabolism. Moreover, the amount of frc gene copies in the investigated soils was detected in the range of 1.64x10(7) to 1.75x10(8)/g of dry soil under oxalogenic tree (representing 0.5 to 1.2% of total 16S rRNA gene copies), whereas the number of frc gene copies in the reference soil was 6.4x10(6) (or 0.2% of 16S rRNA gene copies). This indicates that oxalotrophic bacteria are numerous and widespread in soils and that a relationship exists between the presence of the oxalogenic trees Milicia excelsa and Afzelia africana and the relative abundance of oxalotrophic guilds in the total bacterial communities. This is obviously related to the accomplishment of the oxalate-carbonate pathway, which explains the alkalinization and calcium carbonate accumulation occurring below these trees in an otherwise acidic soil. The molecular tools developed in this study will allow in-depth understanding of the functional implication of these bacteria on carbonate accumulation as a way of atmospheric CO2 sequestration. (c) 2008 Elsevier B.V. All rights reserved.