A PHOTOSYNTHETIC MICROORGANISM IN DARKNESS

VEGA, I.A.; HURST, J.A.; VIALE, A.M.; CASTRO-VAZQUEZ, A.

Huerta Grande - Córdoba

Congreso; I Reunión Conjunta de Sociedades de Biología de la República Argentina; 2007

This caenogastropod ampullariid snail lodges a cyanobacterium within its midgut gland’s cells. Other ampullariid genera, including Pila, which is present in both Asia and Africa, also bear morphologically similar corpuscles. Though this cyanobacterial/ampullariid association may have occurred more than once in phylogeny, one would parsimoniously assume that a single episode of association has occurred, and that the symbiont has been living in darkness even before the fragmentation of Gondwana (>150 My). In free-living cyanobacteria, photosynthetic pigments capture light energy for the production of both sugars and oxygen, with the participation of the enzyme ribulose-bisphosphate carboxylase-oxygenase (RubisCO), so the question was raised to what extent these endocyanobionts may have preserved the photosynthetic hardware of their free-living ancestors. Pigments present in the endocyanobionts were identified as steryl-pheophorbides a and b (through HPLC, mass spectrometry and hydrogen nuclear magnetic resonance analysis). Also, by means of Western blot analysis with antibodies against RubisCO, two bands were detected in protein extracts. We suggest that this microorganism might fix CO2 using RubisCO, although energy sources other than light should have to be used.