DNA replication behaviour of individual nucleoids of two Streptomyces strains

✍ Scribed by Dr. Christel Kummer; Sigrid Kretschmer

• Book ID: 102388867
• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 359 KB
• Volume: 26
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/jobm.3620260409

✦ Synopsis

During exponential growth mycelia of Streptomyces granaticolor and Streptomyces hygroscopicus were pulse-labelled with aH-thymidine for different times. The distribution of silver grains was analyzed in the autoradiograms by using the unit cell-concept, according to which a unit cell corresponds to the hyphal length containing one nucleoid, i. e. one genome equivalent.

All nuclcoids of the mycelia were labelled, if the pulse extended for more than 50% of the doubling time. Thus, in young mycelia there were no nucleoids in which had stopped replication at all. However, the mycelia showed an increasing fraction of non-replicating nucleoids, if the pulse was shortened. This fact indicated that nucleoids transiently lacked replication.

The fraction of non-replicating nucleoids as determined from the latter samples allowed to calculate the replication time C of the individual nucleoids. The C period occupied about 54% of the doubling time in mycelia growing with a generation time of 96 t o 415 min.

Replication of neighboured nucleoids was not synchronous.