Genetic regulation can occur at many different levels -- in fact, if you can imagine a mechanism of genetic regulation it probably exists somewhere. A few examples of levels of regulation known to occur in bacteria include:

• changes in the structure of DNA (e.g., by DNA bending, methylation, protein-binding, or recombination),
• influencing RNA polymerase binding to promoter sequences and initiating transcription (e.g., via binding of repressor or activator proteins),
• premature termination of transcription (e.g., via attenuation),
• influencing the access of ribosomes to the ribosome binding site on the mRNA (e.g., by an antisense RNA)
• modulation of mRNA turnover (e.g., by polyadenylation)
• protein folding (e.g., mediated by chaparones)
• proteolysis
• binding of allosteric effectors (e.g., cofactors)
• covalent modification of proteins (e.g. phosphorylation, adenylation, etc)