1. Microbial characterization of different ecological communities by the employment of a vast array of molecular techniques, including functional and phylogenetic metagenomics, transcriptomics and qPCR. In particular, these approaches have been used to characterize the complex ecosystem represented by the human intestinal microbiota. 2. Using genome sequence data, predicted open reading frames have been searched against known protein and protein motifs databases to identify proteins of probiotic bacteria potentially involved in molecular pathways related to their health-promoting activities. The functional genes have been over-expressed in a heterologous host and their enzymatic activity evaluated by different analytical methods (capillary electrophoresis, spectrophotometry, etc.). 3. Proteomic analysis has been used to catalogue the most abundantly expressed proteins in industrial bacteria. Mass spectrometric identification of the two-dimensional gel-separated proteins and multi-dimensional chromatography coupled with tandem mass spectrometry have been applied for comparative analysis of proteins recovered from bacteria grown in different culture conditions as well as from wild type and mutants. This approach allowed the identification of specific proteins whose expression levels vary in the different strains and culture conditions. 4. Fermentative processes of anaerobic bacteria used in dairy and pharmaceutical products (growth kinetics, productivity and biomass yields) have been studied in batch fermentations. Optimization of fermentative parameters (substrate, pH, pO2, stress condition) was carried out by parallel cultivation experiments performed in 10 small scale bioreactors available in the CIRB laboratory of fermentation. These parallel fermentations allowed the evaluation of the gene expression under different growth conditions.