FINE-STRUCTURE AND IMMUNOLOCALIZATION OF PROTEINS IN APHANIZOMENON SPFROM THE BALTIC SEA

The subcellular arrangement of vegetative cells in the colony-forming cyanobacterium Aphanizomenon sp., collected from blooms in the Baltic Sea in the summer of 1991 and 1992, was characterised by a loose netwo rk of thylakoids with intrathylakoid spaces. The phycobiliprotein phyc oerythrin (PE) was found in vegetative cells at locations correspondin g to thylakoids and similar relative quantities of PE were found in he terocysts, however, the subcellular location was ambiguous in heterocy sts. Cellular inclusion bodies common in cyanobacteria, such as polyhe dral bodies, cyanophycin and polyphosphate granules, were present in m ost vegetative cells but not in heterocysts. A large polyhedral crysta l was present in both cell types. Antibodies against Rubisco did not b ind to this inclusion but to the smaller polyhedral bodies (i.e. carbo xysomes) and free Rubisco in the cytoplasm. In addition, gas vesicles were found to be exclusive to vegetative cells and occasionally microt ubule-like inclusions and spherical membrane inclusions were observed. The putative Aphanizomenon flos-aquae from the Baltic Sea appears to be significantly different in ultrastructure from freshwater A. flos-a quae, and we recommend that, until differences are clarified, the Balt ic form be referred to as Aphanizomenon sp.