Accession Number:

AD0827994

Title:

EVIDENCE THAT TWO MAJOR REPLICONS COMPRISE THE GENOME OF STAPHYLOCOCCUS AUREUS,

Descriptive Note:

Corporate Author:

FORT DETRICK FREDERICK MD

Personal Author(s):

Report Date:

1967-12-01

Pagination or Media Count:

18.0

Abstract:

In Staphylococcus aureus, a pronounced shift in position of the acriflavin resistance locus was observed when gene order was determined by marker frequency analysis of cells of various ages. In young cells 2-hour culture, acriflavin resistance was mapped near the origin of replication, but, in older cells 5-hour culture, the same locus was mapped at the middle of the genome. By the method of synchronous chromosomal replication, acriflavin resistance consistently duplicated in the central portion of the chromosome. When cells from a 2-hour culture were exposed to nitrosoguanidine and then allowed to express mutations after mutagen treatment, novobiocin-resistant mutants were fully expressed after two generations, but acriflavin-resistant mutants were not fully expressed until after five to six generations. In contrast, when cells from a 5-hour culture were similarly treated, both novobiocin resistnce and acriflavin resistance were fully expressed after two generations of growth. Furthermore, the ratio of frequency of acriflavin- resistant mutants to novobiocin-resistant mutants was 2.5 times higher in 2-hour cells than in 5-hour cells. The data have been utilized to demonstrate that the total genome in S. aureus is composed of two replicons. In young cells, one replicon occurs in a much greater number of copies compared with other replicon, but this imbalance of replicon ratio declines considerably in older cells. Nine genes have been examined to date. Three of these genes have been assigned to one replicon, and the other six to the second replicon

Subject Categories:

  • Microbiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE