Abstract: An approach for differentially isolating eukaryotic (plant and animal) DNA from bacterial DNA prior to sequencing using a combination of size exclusion-based separation and differential cell lysis. The method of the present invention exploits the differences of the cellular size and components of each type of organism to be separated. The composition and nature of the cell wall of plant cells, enzymatic sensitivity of bacterial and animal cells and overall size difference of bacterial and plant/animal cells allows one portion of a mixed sample to be lysed while retaining the integrity of the remaining organisms. Separation of one phylogenetic component then permits the remaining components to be extracted with minimal contribution from the preceding component. The separation of DNAs from differing contributing kingdoms in an unknown sample increases interpretability through decreasing complexity in subsequent sequencing applications.