Bacterial gene expression is regulated at the transcriptional level through operons, which distinguish constitutively expressed genes from adaptively regulated genes controlled by repressor proteins that bind an operator region to block RNA polymerase, illustrated by induction (e.g., the lactose operon, activated when a metabolite binds and inactivates the repressor) and end-product feedback repression (e.g., the tryptophan operon, activated when excess product binds and activates the repressor). Genetic variation and evolution in bacteria arise from mutation (base substitutions, frameshift, and deletion/nonsense mutations, whether spontaneous or induced by mutagens) transmitted vertically, and from horizontal gene transfer between cells of the same generation via transformation, transduction, and conjugation, mediated by mobile genetic elements such as plasmids and transposons — core mechanisms within bacterial molecular genetics.
Bacterial gene expression is regulated at the transcriptional level through operons, which distinguish constitutively expressed genes from adaptively regulated genes controlled by repressor proteins …