NONOPSONIC PHAGOCYTOSIS OF PSEUDOMONAS-AERUGINOSA BY MACROPHAGES AND POLYMORPHONUCLEAR LEUKOCYTES REQUIRES THE PRESENCE OF THE BACTERIAL FLAGELLUM

Whereas the mechanism of nonopsonic phagocytosis of Pseudomonas aerugi nosa has been described, the bacterial ligands required are poorly und erstood. To identify the requisite bacterial ligands, studies with iso genic mutants of P. aeruginosa PAK lacking pill, flagella, and the Rpo N sigma factor were undertaken. The RpoN mutant, lacking pill, flagell a, and nonpilus adhesins, bound poorly and was resistant to ingestion by both macrophages and neutrophils. Pill were not absolutely required for binding or phagocytosis of P. aeruginosa. The presence of a flage llum was not required for binding of P. aeruginosa to macrophages but was critical for the subsequent internalization of the bacterium, sugg esting that this factor or a surface ligand associated with its assemb ly was responsible for stimulation of nonopsonic phagocytosis.