Final answer:
Bacterial gene expression is predominantly controlled at the transcriptional level through operons like the lac and trp operons, riboswitches affecting transcription and translation, and RNA polymerase's role in genetic code regulation. Unlikely control stops for bacteria would be those diverging from these established mechanisms.
Step-by-step explanation:
Regulation of Gene Expression in Bacteria
Control of gene expression in bacteria is a critical aspect of their ability to respond to environmental changes. Gene expression in prokaryotic cells like bacteria is primarily regulated at the transcriptional level. The formation of operons, such as the lac operon and trp operon, allows for coordinated regulation of genes involved in common pathways. For instance, the lac operon is an inducible system that is turned on in the presence of lactose and off in its absence. Meanwhile, the trp operon exemplifies repressive control where it is turned off when tryptophan is abundant.
Another regulatory mechanism involves riboswitches and the formation of stem-loop structures at the 5' ends of bacterial mRNAs, which can influence the completion of transcription or prevent translation. Small metabolites and protein interactions may play a part in transitions at these control points as well. Additional layers of regulation include the action of RNA polymerase and the changes in cell responses through modifications in genetic codes as observed through technologies like RNA-seq and mass spectrometry.
Unlikely gene expression control stops for bacteria would deviate from these common mechanisms, which might include post-translational modifications or other eukaryotic-like regulation processes that are not typically found in prokaryotic systems.