Transformation is a form of horizontal gene transfer that occurs when donor bacteria transfer genetic material to the extracellular environment, where it is taken up by recipient bacteria. Transformation in Streptococcus pneumoniae involves competence‑stimulating peptide 1 (CSP‑1), which is secreted by donor cells to signal recipient cells to take up genetic material from the extracellular environment.
Specifically, CSP‑1 binds to regulatory proteins in recipient S. pneumoniae cell membranes and activates the ComABCDE regulatory pathway (also called the ComABCDE regulon). The ComABCDE regulatory pathway involves a cascade activation of regulatory proteins that ultimately stimulate transcription of structural genes that are under the control of different promoters and that encode proteins necessary for the uptake of exogenous genetic material.
Select the statement that best describes how the ComABCDE regulon is controlled.
- negative control and inducible, because CSP‑1 deactivates the membrane receptor, which ultimately turns on transcription of various genes
- negative control and repressible, because CSP‑1 is a repressor of the ComABCDE pathway, which ultimately inhibits transcription
- positive control and repressible, because CSP‑1 binds to membrane receptors and stimulates the regulon, which suppresses transcription at multiple loci
- cannot be determined because no information is provided about the structural genes involved
- positive control and inducible, because CSP‑1 activates the membrane receptor and turns on transcription at multiple genes with different promoters
