Bacterial are a great group of organisms. They have circular
genomes and never went toward linear genomes while other
organisms show the opposite strategy and don't have circular
genomes (disregarding their cytoplasmic genome). Why they have
followed these different strategies? You can package linear
genomes much more efficiently than circular genomes, and
bacteria simply don't require the information density to be
prosperous. To be a bit more specific, it's the torque strain
put on the double-helix while it's being wound that makes the
difference. Linear genomes can be wound around Histones, and
these Histones can be further formed into more complex and dense
patterns so that the DNA of a linear genome is condensed to a
mere fraction of the size it was before. The high density allows
cell division to occur much, much easier than it would otherwise
happen in Eukaryotic cells. Circular genomes cannot get rid of
the torque stresses like linear genomes can. To attempt a
similar packaging scheme as Eukaryotic cel