SUBCELLULAR ELEMENT ANALYSIS OF A CYANOBACTERIUM (NOSTOC SP) IN SYMBIOSIS WITH GUNNERA-MANICATA BY ESI AND EELS

Element analysis using electron spectroscopic imaging (ESI) and electr on energy loss spectroscopy (EELS) was performed in a symbiotic Nostoc sp. strain found in the upper stem tissue of Gunnera monicata, and in Nostoc PCC 9229, a free-living heterocyst-forming cyanobacterium able to enter into symbiosis with the angiosperm Gunnera in reconstitution experiments. ESI and EELS unequivocally identified the four elements nitrogen (N), sulphur (S), phosphorus (P) and oxygen (O) in different inclusion bodies of these biological specimens. High amounts of nitrog en were solely detected in huge cyanophycin granules in vegetative cel ls of the symbiotic Nostoc strain, whereas large polyphosphate bodies, containing high amounts of phosphorus, sulphur and oxygen, could be s een in the free-living Nostoc PCC 9229. The latter were usually not pr esent or, when found, very small in vegetative cells of the cyanobiont .