Researchers report in Science that they have designed bacteria that can detect tumor DNA. The University of California, San Diego-led team engineered Acinetobacter baylyi, which is typically nonpathogenic and can take up environmental DNA from lysed cells. Using their Cellular Assay for Targeted CRISPR-discriminated Horizontal gene transfer, or CATCH, system, the researchers exploited that ability to develop A. baylyi that specially take up only KRAS-mutated DNA from the environment. After doing so, the engineered bacteria acquire kanamycin resistance that can then be detected on antibiotic selection plates. The researchers tested their CATCH approach using DNA from colorectal cancer cell lines, organoids, and tumors, and tested it in vivo in a mouse model of colorectal cancer to find it could distinguish samples with and without cancer. "The detection of gastrointestinal cancers and precancerous lesions is an attractive clinical opportunity to apply this invention," senior author Jeff Hasty from UCSD says in a statement. The researchers caution in their paper, though, that their tool "is not yet ready for clinical application," as further study and development is needed.