A 2-DE proteomic study to detect selenium-induced proteins in a probiotic lactobacillus buchneri strain

Selenium is a nutritionally essential element important for men, animals and microorganisms. The human recommended intake is about 55g/day. Selenium deficiency may be associated with various chronic diseases such as oxidative stress, cardiovascular diseases and some kinds of cancer. Since selenium content in plantbased food depends on its availability from soil, the level of this element in food and feeds varies among regions. There are several potential options to improve human selenium intake such as soil fertilization and supplementation of food. Development and commercialization of organic forms of selenium have initiated a new era in the availability of selenium-enriched products. Selenium enriched chicken, pork and beef can be produced using organic selenium in the diet of farm animals. The use of Se-enriched yeasts and lactobacilli is also an interesting approach to solve seleniumdeficiency: when these microorganisms are added to ice-creams or yogurt, organic form of Se is then released at gut level. In this studywefocused our attention on a Lactobacillus buchneri strain, already commercialized as probiotic strain, able to overaccumulate selenium during its growth in aMRS modified medium supplemented with sodium selenite (2.19 g/l). Our purpose was to understand, by means of a comparative proteomic approach, if selenium addition could modify protein expression causing variations in the metabolism of the strain. Two-dimensional electrophoresis followed by MALDI-TOF/TOF mass spectrometry was performed on Lactobacillus buchneri 26 grown in a MRS medium fortified with selenium and in a control condition (same medium without selenium). The analysis was developed both on the cytosolic and the membrane fraction in the acidic pI range (4-7). From the cytosolic fraction 20 differentially expressed proteins were detected: 15 upregulated and 5 down-regulated. Image analysis on the membrane gels is actually in progress.