Preparation of peptidoglycan-depleted soluble microbial extract

Unknown microbial ligand(s) other than peptidoglycan (PG) in the soluble microbial extract (SME) can induce Dual oxidase (DUOX) activity and generate reactive oxygen species in the Drosophila gut epithelia. We describe a simple method for the preparation of the PG-depleted SME (SME-ΔPG) by treatment with recombinant peptidoglycan recognition protein (PGRP)-LB, a PG-degrading enzyme. (SME-ΔPG) has been successfully used for dissecting the PG-independent immune signaling pathways in Drosophila gut. The (SME-ΔPG) will be a potentially useful material to dissect PG-independent host response to microbes in diverse biological systems.