Characterization of Azotobacter vinelandii deoxyribonucleic acid and folded chromosomes

Abstract

The properties of A. vinelandii DNA and folded chromosomes were studied and compared to those of Escherichia coli as a standard. Based on melting temperature and buoyant density measurements, the guanosine + cytosine content of purified A. vinelandii DNA was 65%, whereas that of E. coli DNA was 50%. The results of renaturation studies showed that the unique DNA sequence lengths of the 2 organisms were similar with C0t1/2 [half renaturation time] values of 7.3 .+-. 0.4 mol .cntdot. s/liter and 7.5 .+-. 0.3 mol .cntdot. s/liter, respectively, for A. vinelandii and E. coli. Folded chromosomes of A. vinelandii sedimented in a centrifugal field at a rate identical to those derived from E. coli, 1600-1700 S. Based on the DNA content per cell and the mass of a single genome, A. vinelandii contains at least 40 chromosomes/cell.