Assay using marked microbial host cell strains

摘要

An assay is provided for determining the presence of contaminating microbial host cells in a culturing vessel containing a microbial host cell strain that utilizes more than one carbohydrate source as a substrate comprising: (a) culturing the microbial host cell strain in the vessel, wherein the strain comprises nucleic acid encoding a polypeptide of interest and is genetically marked so as not to utilize a carbohydrate source as a substrate; (b) plating an isolated sample of culture from step (a) onto culture media supplemented with a carbohydrate source not utilized by the host cell strain as a substrate; (c) incubating the plated cells at a temperature and for a time sufficient for any positive colony to grow to a detectable level; and (d) detecting whether any colonies are growing on the supplemented culture media.