Allantoin as nitrogen source for growth of marine benthic microalgae

Eighteen species of marine microalgae from nine taxonomic classes were tested for axenic growth in light on allantoin as sole nitrogen source. The tests were made at concentration levels of 0 · 125 and 1 · 25 mM allantoin, and were compared with corresponding growth on 0 · 125 mM hypoxanthine taken as control. Only the diatom Nitzschia acicularis showed good growth at the lower concentration, and this growth was comparable to that from equivalent hypoxanthine, suggesting that allantoin may be an expected intermediate in the pathway of purine catabolism. Two other diatoms and a prasinophyte showed generally slow (but ultimately substantial) growth on allantoin at the higher concentration, while all other algae responded with marginal or insignificant growth. It is concluded that allantoin is generally a poor N-source for phytoplankton growth relative to the purines, but certain benthic-type species appear well equipped to utilize it.