Characterization of strains for taxonomic purposes and probiotic applications.

Characterization of strains for taxonomic purposes. The current methodologies used for the characterization of a strain for taxonomic purpose are a combination of those considered traditional and the new one that have been developed recently. In case of strains belonging to novel taxa the characterization needs to provide data for their allocation within the hierarchical framework laid down by the Bacteriological Code. The information on the strain should be as complete as possible and should include the location and the environment peculiarity from which the strain was isolated. Genetic and phenotypic methods are used for characterization. Genotypic criteria refers to sequence analysis of the 16S rRNA gene, DNA-DNA hybridization, DNA base composition, sequencing of the housekeeping genes. Phenotypic criteria typically comprises parameters such as cell shape, colony morphology, biochemical properties, pH and temperature optima etc. In addition, chemotaxonomy is in essence a part of the phenotypic characterization. Characterization of strains for probiotics applications. Functional characterization of probiotic strains have been performed in our laboratory regarding humans , animals and plants. Three examples are reported. The application to humans aimed at the characterization of Bifidobacterium strains capable of inhibiting pathogens typical of the infant gastrointestinal tract. After a preliminary screening regarding the antimicrobial properties against coliforms, Escherichia coli, Salmonella enteriditis, and Clostridium difficile strains, the most interesting Bifidobacterium strains were characterized for cytotoxic effects, adhesion to gut epithelium cell lines and for their ability to stimulate gut health by increasing the metabolic activity and the immune response of epithelial cells. The examination of all these features allowed the identification of three Bifidobacterium breve strains and a Bifidobacterium longum subsp. longum strain as potential probiotics for the treatments of enteric disorders in newborns such as infantile colics. The application to animals regarded the characterization of probiotic strains for the reduction of Campylobacter spp. levels in poultry aimed at increasing the safety of poultry meat. Within this work, a synbiotic mixture was developed, composed of a galactooligosaccharide combined with a probiotic Bifidobacterium strain (B. longum subsp. longum PCB133), characterized for its antimicrobial activity against C. jejuni. A significant reduction of C. jejuni in poultry feces was obseved in the treated chickens. The application to plants focused on the inoculation of microorganisms to improve plant growth and root development of perennial ryegrass. A microorganism-based commercial product was used to amend hydroponically grown Lolium perenne L. and results compared with the use of the same filtered product, a phytohormone solution and an untreated control. The main microbial groups present in the product were identified, evidencing bacterial and yeast species, including several Lactobacillus strains. The microbial composition of sand and root samples was investigated by PCR-DGGE, showing different profiles in the different treatments. Inoculated lactobacilli were found to be able to colonize plant roots. Plants treated with the product showed an increased resistance to tearing out with respect to other treatments and roots were longer with respect to the control.