Test GIF (IMAGE) California Institute of Technology Caption DNA markers show up as fluorescing dots in the test, making them easy to count. Here, the test shows a bacterial sample grew more poorly in an antibiotic solution, indicating that it does not have resistance to that antibiotic. Credit Caltech/Matthew Curits Usage Restrictions None 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.