Optimal levels of the essential amino acids histidine, lysine and threonine in Caenorhabditis elegans maintenance medium

Abstract

AbstractCurrent Caenorhabditis elegans Maintenance Medium (C-CeMM) is used to cultivate the free-living nematode, C. elegans. In C-CeMM, ten amino acids (AA) were found to be nutritionally essential. The optimal requirements of seven of these ten essential AA were determined previously. The objectives of the present study were to determine the optimal requirements of the remaining three essential AA: histidine, lysine and threonine. The Optimal Caenorhabditis elegans Maintenance Medium (O-CeMM) was formulated using the levels of all essential AA that supported the optimal population growth for C. elegans from previous quantitative studies and from the results obtained in the first part of this study. The efficacy of O-CeMM, C-CeMM, as well as Egg CeMM (E-CeMM), based on the essential AA ratio in hen's egg, was studied. The optimal requirements (mg ml–1) of histidine, lysine and threonine were determined to be 2.26 (8× C-CeMM), 1.03-2.06 (1× to 2× C-CeMM), and 0.717-2.86 (1× to 4× C-CeMM), respectively. It was found that O-CeMM supported a significantly higher (1.55 ∼ 1.60×) population growth (number of nematodes/ml) when compared with C-CeMM and E-CeMM. For both O-CeMM and C-CeMM, the AA efficiency ratio (AAER; g dry weight (wt) gain of C. elegans/g of total AA) was determined to be 0.18, which was significantly higher than the 0.15 that was determined in E-CeMM. Although the O-CeMM supported a significantly higher population growth, a higher level of histidine and consequently higher total AA were used in O-CeMM than in C-CeMM. Therefore, based on the findings on AAER, it was concluded that both the O-CeMM and C-CeMM were equally efficient for the cultivation of C. elegans.