Utilization of aminolevulinic acid as a nitrogen source by a green alga

Cells of the green alga Golenkinia, pre-cultured so that the contribution of any nitrogen source other than delta-aminolevulinic acid (ALA) to endogenous nitrogen reserves is minimal or absent, are capable of sustained growth on ALA as the sole source of nitrogen in either light or dark. Yield is proportional to ALA concentration up to 10 mM; higher concentrations are increasingly inhibitory. This optimal concentration supports cell numbers, growth rates and chlorophyll levels equal to those found using the same concentration of nitrate. These findings support the suggestion that ALA is not committed to porphyrin synthesis and indicate that conclusions regarding regulation of chlorophyll synthesis based on long-term addition of ALA to systems sensitive to carbon/nitrogen levels in the medium be reconsidered.