Metabolic Characterization of Supernatants Produced by spp. With Anti- Activity.

is an organism of public health interest for its presence in water supply systems and other humid thermal habitats. In this study, ten cell-free supernatants produced by strains were evaluated for their ability to inhibit strains isolated from hot tap water. Production of antimicrobial substances by strains were assessed by agar well diffusion test on BCYE agar plates pre-inoculated with Cell-free supernatants (CFS) showed antimicrobial activity against all strains tested: and showed the highest activity. By means of a proton-based nuclear magnetic resonance (H-NMR) spectroscopy, we detected and quantified the metabolites of these CFSs, so to gain information about which metabolic pathway was likely to be connected to the observed inhibition activity. A panel of metabolites with variations in concentration were revealed, but considerable differences among inter-species were not showed as reported in a similar work by Foschi et al. (2018). More than fifty molecules belonging mainly to the groups of amino acids, organic acids, monosaccharides, ketones, and alcohols were identified in the metabolome. Significant differences were recorded comparing the metabolites found in the supernatants of strains grown in MRS with glycerol and the same strains grown in MRS without supplements. Indeed, pathway analysis revealed that glycine, serine and threonine, pyruvate, and sulfur metabolic pathways had a higher impact when strains were grown in MRS medium with a supplement such as glycerol. Among the metabolites identified, many were amino acids, suggesting the possible presence of bacteriocins which could be linked to the anti- activity shown by cell-free supernatants.