Synthesis of Thiamine and Folic Acid by Nocardia rhodnii, the Micro-symbiont of Rhodnius prolixus

Abstract

STRONG suggestive evidence¹ exists to support earlier proposals² that Nocardia rhodnii, the extracellular symbiont of Rhodnius, contributes essential food factors to its host. In recent years, however, the evidence has been conflicting, particularly where it concerns the nature of these factors. In 1954, Geigy, Halff and Kocher³ isolated a micro-organism from Triatoma infestans similar to N. rhodnii and found that whereas it synthesized thiamine and other vitamins in minimal amounts, there was a 2,500-fold hyper-production of folic acid. Bewig and Schwartz⁴, however, later claimed that this organism was not N. rhodnii, and was not symbiotic. They showed that pure cultures of N. rhodnii on an elaborate semi-synthetic medium synthesized minimal amounts of folic acid, no vitamin B₁₂ and no folininic acid. They found too that injection of vitamins into sterile Rhodnius failed to induce moulting. In 1956 Baines⁵, using feeding and injection techniques, came to the conclusion that Rhodnius is dependent on N. rhodnii for pyridoxine, calcium pantothenate, nicotinamide and thiamine, but that biotin and folic acid are present in adequate concentration in the host blood to meet the requirements of Rhodnius.