  Inspired by recent experiments on the spatial organization of bacterial
chromosomes, we consider a type of "bottle brush" polymer consisting of a
flexible backbone chain, to which flexible side loops are connected. We show
that such a model with an open linear backbone spontaneously adopts a helical
structure with a well-defined pitch when confined to small cylindrical volume.
This helicity persists over a range of sizes and aspect-ratios of the cylinder,
provided the packing fraction of the chain is suitably large. We analyze this
results in terms of the interplay between the effective stiffness and actual
intra-chain packing effects caused by the side-loops in response to the
confinement. For the case of a circular backbone, mimicking e.g. the E. coli
chromosome, the polymer adopts a linearized configuration of two parallel
helices connected at the cylinder poles.
