A large number of prokaryotes do indeed have nucleosome-like structures. The most well studied is H-NS in _E. coli_ , _Salmonella_ and some other deltaproteobacteria. H-NS like molecules have also been found in mycoplasma (Lsr2). One of its roles is to bind AT-rich DNA and silence transcription. The binding is usually to suppress the expression of foreign DNA which tends to have a lower GC content than the host organism. There is a great paper that did ChIP on ChIP with H-NS in _Salmonella_ by Navarre et al in Science (Pubmed ID: 1676311).
As a side note H-NS does compact DNA and there is a paper by Dame et al. that demonstrates it with atomic force microscopy.