EPIFLUORESCENCE MICROSCOPY OF ANABAENA SP - NUCLEOID CONFIGURATIONS AND EVIDENCE FOR INCLUSION-ASSOCIATED DNA

Vital staining of the nucleoid in Anabaena sp. PCC7118 was performed u sing the double stranded DNA-specific fluorochrome DAPI. In the unicel lular mutant, the central epifluorescent zone had a dense skein config uration, while in the filamentous parent strain protrusions, lobes, an d distinct isolated elements of the nucleoid were visible. Both varian ts contrasted with the mainly peripheral, partitioned structure typica l of plastids and prochlorophytes. Blue-white emittance from the DNA-D API complex was maximum in dividing cells, suggesting that DNA configu ration is linked to the cell cycle events. In stationary cultures, epi fluorescent cell inclusions were conspicuous: based on this observatio n, we argue that DNA is associated with carboxysomes in situ.