NUCLEOID STRUCTURE ACID DISTRIBUTION IN THERMOPHILIC ARCHAEA

Nucleoid structure and distribution in thermophilic organisms from the Archaea domain were studied, Combined phase-contrast and fluorescence microscopy of DAPI (4',6-diamidino-2-phenylindole)-stained Sulfolobus acidocaldarius and Sulfolobus solfataricus cells revealed that the nu cleoids were highly structured. Different nucleoid distribution within the cells, representing different partition stages, was observed, The conformation of the nucleoids differed between exponentially growing and stationary-phase cells. Also, the stationary-phase cells contained two chromosomes, and the nucleoids occupied a larger part of the inte rior of the cells than in the exponentially growing cells, The part of the cell cycle during which fully separated nucleoids could be detect ed was short, Since the postreplication period is long in these organi sms, there was a considerable time interval between termination of chr omosome replication and completion of nucleoid separation, similar to the G(2), phase in eukaryotic cells, The length of the visible cell co nstriction period was found to be in the same range as that of eubacte ria. Finally, cell-cell connections were observed under certain condit ions. Possible eubacterial, eukaryotic, and unique features of nucleoi d processing and cell division in thermophilic archaea are discussed.