Characterization of deoxyribonucleic acid of Entamoeba histolytica by cesium chloride density centrifugation
摘要：
Buoyant density of deoxyribonucleic acid (DNA) from Entamoeba histolytica was determined in cesium chloride gradients in the analytical ultracentrifuge. The DNA was extracted from fresh or lyophilized cells in a solution containing 8 M urea. It was purified by absorption on and elution from hydroxylapatite, and on a cesium chloride gradient in the preparative ultracentrifuge. DNA from axenically grown amebae contained a single component and it banded in the region of 1.69 g/ml. DNA prepared from 13 strains of amebae grown with penicillin-inhibited bacterial cells also banded in this region. Some of the latter preparations contained a second component of buoyant density 1.708 g/ml which is attributed to the food bacteria, Bacteroides symbiosus. Buoyant density of amebal DNA ranged from 1.6881 to 1.6913 g/ml corresponding to guanine plus cytosine contents of 27.5 to 30.8 mole per cent. Buoyant density is not a sensitive parameter for making interstrain distinctions among strains of E. histolytica, but it appears to offer promise in an area where little else has succeeded. A number of statistically significant interstrain differences were encountered. Thus low density DNA from NRS or HK9 strains was distinguished from DNA of intermediate density from DKB or 200 strains and from the high density DNA of the F22 strain at probability levels to 0.001. Guanine plus cytosine contents calculated from thermal hyperchromicity (Tm) were lower than those calculated from buoyant density data. The DNA from Bacteroides symbiosus was calculated to contain 48.2 mole per cent guanine plus cytosine, using buoyant density data.
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DOI：
10.2307/3277839
被引量：
年份：
1971
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