Two-dimensional DNA electrophoresis applied to the study of DNA methylation and the analysis of genome size in Myxococcus xanthus

Methylation changes in the DNA of Myxococcus xanthus were studied using a twodimensional DNA electrophoresis technique in which one-dimensional polyacrylamide separations of HpaII digests of DNA extracted from different stages of development were re-digested in situ with MspI and then run in a second dimension. Specific methylation events were seen to be associated with the slowing down of cell growth as vegetative cells entered stationary phase, and also as cells on starvation agar progressed through developmental stages. Two-dimensional agarose electrophoresis was employed to obtain an unambiguous estimate of the genome size of this organism, approximately 5690 × 10³ base-pairs (±9%). Using the same method, the Escherichia coli genome was measured to be 3520 × 10³ base-pairs (±7%).