Determination of the size of the Azotobacter vinelandii chromosome.
The chromosome of Azotobacter vinelandii UW was digested separately with the rape cutter restriction endonucleases SwaI (5'-ATTTAAAT), PmeI (5'GTTTAAAC) and PacI (5'-TTAATTAA) and the products were separated by pulsed-field gel electrophoresis. The size of the chromosome was determined to be approximately 4.5 megabase pairs (Mb) based on the sum of the sizes of the restriction fragments. This is almost the same as the size of the chromosome of Escherichia coli. The inability of the undigested DNA to enter the gel has led us to infer that the chromosome is circular.