Selenium effects on the metabolism of a Se-metabolizing Lactobacillus reuteri: analysis of envelope-enriched and extracellular proteomes.

Selenium (Se) has received great attention in the last few years, as it is considered to be essential for human health (prevention of viral infections, heart diseases and ageing-related diseases). Se deficiency can be counteracted by the administration of selenium-enriched probiotics that are able to convert inorganic selenium into less toxic and more bio-available organic forms. This study was performed on Lactobacillus reuteri Lb2 BM DSM 16143, a probiotic LAB previously demonstrated to be able to fix Se into selenocysteines. The aim was to assess Se influence on its metabolism, by a 2-DE proteomic approach, on two different cellular districts: envelope-enriched and extracellular proteomes. While in the envelope-enriched fraction 15 differentially expressed proteins were identified, in the extracellular proteome no quantitative difference was detected. However, at a molecular level, we observed the insertion of Se into selenocysteine, exclusively under the stimulated conditions. The obtained results confirmed the possibility to use L. reuteri Lb2 BM DSM 16143 as a carrier of organic Se that can be easily released in the gut becoming available for the human host.