Metabolism of Endothall by Aquatic Microorganisms

[¹⁴C]Endothall [7-oxabicyclo(2.2.1)heptane-2,3-dicarboxylic acid] labeled in the oxabicyclo ring was readily degraded by microorganisms in lake water and hydrosoil through a pathway involving splitting of the ring. An Arthrobacter species isolated from hydrosoil by the enrichment method was able to utilize endothall as the sole source of carbon and energy for its growth. The 14C from endothall was incorporated into cellular amino acids, proteins, nucleic acids, and lipids and was also released as ¹⁴CO₂. After short-term incubation of the Arthrobacter with [¹⁴C]endothall, ¹⁴C was incorporated into citric, aspartic, and glutamic acids and some unidentified compounds. [¹⁴C]Glutamic acid accounted for a large proportion of the total ¹⁴C incorporated into the alcohol-soluble cell fraction. Treatment with 2 × 10 ^-2 M monofluoroacetate caused a severalfold accumulation of [¹⁴C]citric acid, but only partially inhibited the incorporation of ¹⁴C into glutamic acid. It appears, therefore, that the ¹⁴C from ¹⁴C-ring-labeled endothall is incorporated into glutamic acid via the tricarboxylic acid cycle and an alternate, unknown pathway.