Studies on the pyocins of Pseudomonas aeruginosa: morphology and mode of action of contractile pyocins.

The adsorption and inhibitory action of pyocin 21 on sensitive cells of Pseudonzonas aeruginosa (P. pyocyanea) were observed by fluorescence microscopy and by using agar cultures. By electron microscopy, preparations from four pyocinogenic strains of P. aeruginosa were seen to include contracted and uncontracted particles, isolated tail cores and sheaths, The importance of adsorption and contraction of the particles on the surface of sensitive bacteria for the inhibitory action of these pyocins is suggested by the following evidence : ( I ) Particles adsorbed to sensitive bacteria a t o "C, but contraction of particles was not then observed and the bacteria were not disrupted. ( 2 ) Pyocin particles did not adsorb to pyocin-resistant bacteria. (3) The ability to adsorb to sensitive bacteria and to kill them was absent after removal of the contractile sheath with sodium dodecyl sulphate. (4) When treated with homologous antiserum, pyocin activity was neutralized and the agglutinated particles remained unadsorbed and uncontracted. ( 5 ) Bacterial receptors for contractile pyocins contain lipopolysaccharide ; such extracts from sensitive, but not from resistant, cells of P. aeruginosa inactivated pyocins, and contracted particles were seen adsorbed to lipopolysaccharide fragments.