Biotin Requirement and Its Biosynthesis Blockage in the Free‐living Nematode, Caenorhabditis elegans

Abstract

The free living C. elegans were cultivated in the chemically defined C. elegans Maintenance Medium (CeMM) supplemented with 0, 0.00600, 0.0300, 0.150, 0.750, 3.75, 18.8, 93.8 and 469 μg/ml biotin. No population growth was observed when biotin was omitted from the CeMM (0 μg/ml). A significantly decreased population growth (p ≤.05) was observed at 0.00600 μg/ml biotin. Optimal population growth occurred at biotin levels between 0.0300 and 18.8 μg/ml. However, the nematodes appeared to move sluggishly at 0.0300 and 0.150 μg/ml biotin. These results, therefore, suggested that 0.75 to 18.8 μg/ml were the optimal range to support a maximal growth of C. elegans as well as to prevent sluggish movement resulted from a biotin deficiency. Significant reductions of population growth (p ≤.05) were observed at 93.8 μg/ml and 469 μg/ml biotin. In the blockage experiment, dethiobiotin, the last‐step precursor in the biotin biosynthesis pathway, was used to investigate if it supported the population growth of C. elegans. Three levels of dethiobiotin (0.0263, 0.132, and 3.29 μg/ml) were used to replace biotin at the equal molar concentrations, respectively, in the CeMM. At all three levels of dethiobiotin, no population growth of C. elegans was observed. These finings suggested that C. elegans might have lost the ability to produce the enzyme, biotin synthase. Therefore, biotin became a dietary essential nutrient for C. elegans. (Supported by San Jose State University Foundation Grant and Circle of Friends Research Award of Department of Nutrition & Food Science, San Jose State University, CA)