| Summary: | Lactic acid bacteria (LAB) resist sodium selenite of concentrations greater than 100 mg/L in fermentation media. Selenium affects the growth rate, but once the microorganism absorbs selenium, this element is converted through a complex mechanism into selenocysteine and then into a selenoprotein structure. This study verified the presence of selenocysteine in <i>Enterococcus faecium</i> ABMC-05. The microorganism was cultivated in a medium enriched with a minimum inhibitory concentration of sodium selenite (184 mg/L). The concentration of selenium absorbed and the bioconversion into selenocysteine were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and reverse-phase high-performance chromatography (RP-HPLC), respectively. The presence of the <i>sel</i>D, <i>sel</i>A, and <i>cys</i>K genes was determined by amplifying the 16S rDNA through polymerase chain reaction (PCR). The microorganism accumulated inorganic selenium, and part was transformed into selenocysteine. The growth curves were atypical for a lactic acid bacterium with a stationary phase greater than 70 h. Determining the genetic expression showed only the presence of the <i>cys</i>K gene and the absence of the <i>sel</i>D and the <i>sel</i>A genes. The results demonstrate that this microorganism produces selenocysteine through a mechanism independent of the SelA and SelD pathways in contrast to other LAB.
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