Method for fluorescent marker swapping and its application in Steinernema nematode colonization studies.

An allelic exchange vector was constructed to replace gfp by mCherry in bacteria previously tagged with mini-Tn5 derivatives. The method was successfully applied to a gfp-labeled Yersinia pseudotuberculosis strain and the re-engineered bacterium was used to study the colonization of Steinernema nematodes hosting their Xenorhabdus symbiont using dual-color confocal microscopy.