sentences:  He retired in 1991.In his 1963 paper "The bacterial chromosome and its manner of replication as seen by autoradiography", Cairns demonstrated by autoradiography that the DNA of the bacterium "Escherichia coli" was a single molecule that is replicated at a moving locus (the replicating fork) at which both new DNA strands are being synthesized.Subsequently, it was found that there were in fact two moving forks, traveling simultaneously in opposite directions around the chromosome.