BIPOLAR LOCALIZATION OF THE REPLICATION ORIGIN REGIONS OF CHROMOSOMESIN VEGETATIVE AND SPORULATING CELLS OF BACILLUS-SUBTILIS

To investigate chromosome segregation in B. subtilis, we introduced ta ndem copies of the lactose operon operator into the chromosome near th e replication origin or terminus. We then visualized the position of t he operator cassettes with green fluorescent protein fused to the Lad repressor. In sporulating bacteria, which undergo asymmetric cell divi sion, origins localized near each pole of the cell whereas termini wer e restricted to the middle. In growing cells, which undergo binary fis sion, origins were observed at various positions but preferentially to ward the poles early in the cell cycle. In contrast, termini showed li ttle preference for the poles. These results indicate the existence of a mitotic-like apparatus that is responsible for moving the origin re gions of newly formed chromosomes toward opposite ends of the cell.