Abstract: The present disclosure is drawn to methods of utilizing nucleic acid barcodes and corresponding amplifying sites in cells in which the barcodes naturally occur. These barcodes and amplifying sites are reconfigured into a single nucleic acid cassette that provides for ease of use in tagging particular species, strains, or variants of cells, each with a different barcode. These barcodes can be used to track the colonization capabilities of the barcoded cells. The present disclosure further provides for assays that utilize natural barcodes to measure relative microbial colonization ability of a plant root system.