METABOLIC-FATE OF ENERGETIC AMINO-ACIDS IN THE APOSYMBIOTIC PEA APHIDACYRTHOSIPHON-PISUM (HARRIS) (HOMOPTERA, APHIDIDAE)

Amino acid metabolism of aposymbiotic pea aphids obtained by an antibi otic treatment was analysed by the use of C-14-radiolabeled tracers in isotopic equilibrium, and compared with data obtained previously in s ymbiotic conditions. The interconversions between energetic amino acid s were little affected, but the synthesis of three essential amino aci ds (threonine, isoleucine and lysine) from carbons of common amino aci ds was interrupted after antibiotic treatment. An accumulation of glut amate from precursors normally converted to these essential amino acid s and an increase of glutamate or glutamine in the honeydew plus exuvi ae of aposymbiotic aphids were likewise observed. These results valida te the role of the symbiotic bacteria in the synthesis of essential am ino acids.