Bacterial strategies to evade natural or human-imposed antibiotics are varied and include membrane-bound efflux pumps that export antibiotics from the cell. A review of efflux pumps [Grkovic, S., et al. (2002)] states that, because energy is required to drive the pumps, activating them in the absence of the antibiotic has a selective disadvantage. The review also states that a given antibiotic may play a role in the regulation of efflux by interacting with either an activator protein or a repressor protein, depending on the system involved. How might such systems be categorized in terms of negative control (inducible or repressible) or positive control (inducible or repressible)?

Key Concepts

Efflux Pumps

Efflux pumps are membrane proteins that actively transport substances, including antibiotics, out of bacterial cells. This mechanism helps bacteria resist the effects of antibiotics by reducing their intracellular concentrations. The energy required for this process typically comes from ATP hydrolysis or proton motive force, making it an active transport system.

Gene Regulation

Gene regulation refers to the mechanisms that control the expression of genes, determining when and how much of a gene product is made. In the context of efflux pumps, regulation can occur through activator or repressor proteins that respond to the presence of antibiotics, influencing whether the efflux pump is turned on or off. This regulation can be categorized as negative or positive control.

Negative and Positive Control

Negative control involves the inhibition of gene expression, where a repressor protein binds to DNA to prevent transcription, while positive control enhances gene expression through activator proteins that promote transcription. Systems can be classified as inducible, where the presence of a substance (like an antibiotic) triggers expression, or repressible, where the presence of a substance inhibits expression, depending on the regulatory mechanisms involved.