Polarized Relationship of Bacterial Spore Loci to the "old" and "new" Ends of Sporangia

The frequency of association of spore loci with the "old" and "new" ends of rod-shaped sporangia in batch cultures of Bacillus megaterium ATCC 19213 was estimated by phase contrast microscopy. The analysis was facilitated by (i) the association of most of the sporangia into chains of two to five sporangia and (ii) the occurrence of two types of cross wall distinguishable by their degree of splitting. It was concluded that a newly formed spore is located at the "old" end of a sporangium. By inference, the sporulation division septum locus is distal to the ultimate normal cell division septum, i.e., proximal to the "old" pole of the B. megaterium sporangium. This result is discussed in relation to deoxyribonucleic acid segregation during sporulation.