Bacterial Colonies on Tetracycline Plates (IMAGE) Institute of Science and Technology Austria Caption Bacterial colonies with a fluorescent reporter protein appearing on tetracycline plates over three days (left to right). Bacteria can grow and form colonies either due to single-step mutations that activate the tetracycline pump gene (dark colonies, present early on), or due to "amplifications" that increase the copy number of the gene (bright colonies), which appear over time. Amplifications, as well as some other mutation types depend on genes in the chromosomal neighborhood of the resistance gene. Credit Magdalena Steinrück Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.