Visualization of a Cell Wall Hydrolase Inhibitor in Fusobacterium nucleatum by Immunofluorescence Microscopy

Innately present in tears, saliva and mucosal secretions, lysozyme provides a critical defensive strategy to the host by cleaving the β-1,4-glycosidic bonds between N-acetylmuramic acid and N-acetyl-D-glucosamine residues of peptidoglycan of invading bacteria, leading to bacterial lysis. To counter this class of cell wall hydrolase enzymes, bacteria produce several lysozyme inhibitors, a representative of which, MliC, was identified in Escherichia coli, Pseudomonas aeruginosa, and various bacterial species. The Gram-negative oral anaerobe Fusobacterium nucleatum encodes an uncharacterized lipoprotein homologous to MliC, whose localization is unknown. Here, we provide an experimental procedure to localize this MliC-like lipoprotein by employing immunofluorescence microscopy. In principle, this protocol can be used for any bacterial system to monitor protein localization.