Analysis of Nucleoid Morphology during Germination and Outgrowth of Spores of Bacillus Species

After a few minutes of germination, nucleoids in the great majority of spores of Bacillus subtilis and Bacillus megaterium were ring shaped. The major spore DNA binding proteins, the α/β-type small, acid-soluble proteins (SASP), colocalized to these nucleoid rings early in spore germination, as did the B. megaterium homolog of the major B. subtilis chromosomal protein HBsu. The percentage of ring-shaped nucleoids was decreased in germinated spores with lower levels of α/β-type SASP. As spore outgrowth proceeded, the ring-shaped nucleoids disappeared and the nucleoid became more compact. This change took place after degradation of most of the spores' pool of major α/β-type SASP and was delayed when α/β-type SASP degradation was delayed. Later in spore outgrowth, the shape of the nucleoid reverted to the diffuse lobular shape seen in growing cells.