The formation of rhizopterin and formylated folate polyglutamates during the growth of Staphylococcus epidermidis

Abstract

The distribution of various folate forms during the growth of Staphylococcus epidermidis is described. Cellular-free folate activity (pteroate-like substances and mono- and di-glutamate folates) was quite prevalent in the early and mid-log phase of growth, but subsequently reached a minimal level in the stationary phase of growth. This free folate activity was identified as rhizopterin, with an extremely small amount of folic acid per se also being found. Cellular polyglutamate folates (folate conjugates with three or more glutamic acid units) were found in relatively high amounts throughout growth, and for any cellular sample constituted most of the total folate activity. The polyglutamate folate compounds were identified as formylated derivatives. A biosynthetic pathway from rhizopterin to the formylated polyglutamate folates is proposed.