Covalently closed minicircular DNA in Micrococcuslysodeikticus

Lee, Chong Sung; Davidson, Norman

doi:10.1016/0006-291x(68)90304-5

Cited by 21 publications

(7 citation statements)

References 2 publications

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“…There have also been a number of reports of the isolation from various bacteria of supercoiled circular molecules which have not been correlated with a specific genetic function (7,9,17,26). All of the V. cholerae P-strains that we examined had a small amount of circular DNA, detectable in some of our experiments, whose possible function remains unclear.…”

Section: Discussionmentioning

confidence: 78%

Isolation and Characterization of the Fertility Factor P of Vibrio cholerae

et al. 1973

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Vibrio cholerae strains with the transmissible fertility factor P contained a supercoiled circular deoxyribonucleic acid (DNA) component amounting to between 2 and 6% of the total DNA obtained from the cells. Such a component was not observed in V. cholerae strains lacking the fertility factor. This supercoiled circular DNA was isolated from P+ cells, and the molecular weight was determined by sedimentation velocity experiments and electron microscopy to be approximately 80 million daltons. These supercoiled circular DNA molecules, which have a guanine plus cytosine (G + C) composition of 42%, were concluded to be the extrachromosomal P factor. It was calculated that there is approximately one copy of the P factor per chromosome. A small amount of,supercoiled circular DNA was occasionally isolated from the Pstrains of V. cholerae. The function of this component, which has a molecular weight of 40 million daltons, is not known. The molecules found in the Pstrains were readily distinguished from the P+ circular molecules by their smaller molecular weight and different G + C composition. Recombination of chromosomal genes inVibrio cholerae depends on the presence of a fertility factor designated P (3, 4). V. cholerae strains containing this factor are referred to as P+ and behave as donor strains. V. cholerae cultures lacking the P factor, which can act as recipients, are termed P-. Although the recombination frequency for chromosomal characters in matings between P+ and Pstrains is low, the P factor itself is transmitted at high frequency from P+ to P-cells. Apparently, the P factor only occasionally causes transfer of chromosomal genes. High-frequency donors, similar to the Hfr types of Escherichia coli in which the fertility factor is chromosomally fixed, have not been found in the V. cholerae mating system.A number of recent studies have established that fertility agents as well as other plasmids exist as autonomously replicating deoxyribonucleic acid (DNA) molecules, functionally and physically distinct from the bacterial chromosome. In this extrachromosomal state, such elements can be isolated as supercoiled circular DNA molecules (13). In the present . 90024. report, we describe the isolation of the P factor from the P+ V. cholerae strains and its characterization as a supercoiled circular DNA molecule.MATERIALS AND METHODS Media. Meat extract agar (MEA) and Difco brain heart infusion (BHI) broth were used for routine cultivation of the V. cholerae strains. The nutrient gelatin agar (NGA) used for the lacunae assay was described by Enomoto (10). Tritium-labeled DNA was isolated from cells grown in the minimal medium for V. cholerae described by Bhaskaran and Rowley (5) to which 1% casein hydrolysate and 20 gCi of 3Hthymidine/ml (specific activity 6.7 Ci/mmole) was added.Bacterial strains. All bacterial strains used are listed in Table 1. The P+ strains were lyophilized to ensure active donor cultures, and a fresh vial was opened for each experiment. Infection of nondonor strains with the P factor. Amounts ...

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Section: Discussionmentioning

confidence: 78%

Isolation and Characterization of the Fertility Factor P of Vibrio cholerae

et al. 1973

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“…Many sex factors and other plasmids carry determinants of phage resistance (154,286) which often involves DNA restriction-modification. Resistance determinants for phages tau (97) and T3, of which the latter is a restricting system (233), are the only somatic functions aside from fertility known for F. Phage restriction is also the only known somatic function of sex factor A (5).…”

Section: Phage and Uv Resistancementioning

confidence: 99%

Extrachromosomal inheritance in bacteria.

Novick¹

1969

Bacteriological Reviews

223

157

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“…It will not be the intention of this review to consider in any detail many of the genetic and physiological properties of bacterial plasmids which have been extensively dealt with in a number of recent reviews and symposia (71,168,178,247,252), nor will the physical aspects of those plasmids with no clear genetic or physiological function (30,54,125,154,206) be examined, nor yet those that can be regarded as phages (166,214). In general, the main emphasis will be on the physical characteristics of those plasmids, with clearly defined properties, that are not phages and, wherever possible, the relationship of their genetic and molecular properties.…”

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confidence: 99%