Tomás Huerta

Rapid Characterization of Four Species of the Saccharomyces Sensu Stricto Complex According to Mitochondrial DNA Patterns

Several strains of the four sibling species of the genus Saccharomyces (S. bayanus, S. cerevisiae, S. paradoxus, and S. pastorianus) were characterized by using a rapid and simple method of restriction analysis of mitochondrial DNA. Patterns obtained with four-cutter endonucleases (such as AluI, DdeI, HinfI, and RsaI) made it possible to differentiate each species. S. cerevisiae and S. paradoxus presented a greater number of large fragments than S. pastorianus and S. bayanus with all the assay enzymes. With AluI and DdeI, species-specific bands clearly permitted differentiation between S. pastorianus and S. bayanus. To test the resolution of this method, wild Saccharomyces strains were analyzed. The correct assignment of these strains to a known taxon by this rapid method was confirmed by means of electrophoretic karyotyping.

Microbiological and physico-chemical aspects in dry-salted Spanish ham.

The main microbiological and physico-chemical parameters in dry-salted ham previously selected were determined during the elaboration process. All determinations were performed at 2 levels: surface and internal. The selected microbiological parameters were: total aerobes, halotolerant, lactic acid bacteria, yeasts and hazardous microorganisms. NaCl, nitrate, nitrite, water activity, moisture, pH, temperature and loss of weight were selected for the physico-chemical study. All microbial groups showed a similar behaviour, increasing along the first stages up to the third month of drying, then decreasing to numbers similar to the initial ones. Only the halotolerants maintained fairly high numbers during the last stages. Some groups were almost absent at internal levels. The hazardous bacteria showed different behaviour: whereas the faecal streptococci were fairly abundant during the whole study, coliforms almost disappeared at the final stages.

Phylogenetic relationships among wine yeast strains based on electrophoretic whole-cell protein patterns

In the present work, a phylogenetic study based on protein electrophoretic profiles of Saccharomyces strains isolated from different Spanish wine regions has been carried out. Qualitative differences between the protein electrophoregrams were found at inter- and intraspecific level, but not between electrophoregrams of strains isolated at the same ecosystem. The numerical analysis of these results allowed us to conclude that intraspecific relationships are determined by ecological factors, as well as human influences (dispersion and artificial selection). A correlation between ecological and/or geographical origin and the relationships among strains was observed.