Morphological Studies on Relaxed and Contracted Forms of Purified Pyocin Particles

Abstract

The bacteriocin from Pseudomonas aeruginosa, pyocin, consists of a contractile sheath and inner core reminiscent of T-even coliphage tails. Contraction of the outer sheath was found to be promoted by 0.5 M magnesium chloride, 1 % Formalin, low pH, sonic treatment, and freezing or thawing or both. The contraction caused by 0.5 M magnesium chloride, however, was found to be reversible and occurred upon reduction of the salt concentration from 0.5 to 0.02 M. In addition, direct assay showed that pyocin activity was nearly proportional to the percentage of only uncontracted forms. Initial studies suggested that the adsorption of purified pyocin onto cell wall fragments from the sensitive indicator strain of P. aeruginosa occurs with the relaxed particle only and not with the contracted form. However, after adsorption, contraction occurred. Various morphological structures, such as tail fibers and base-platelike appendages, were also observed. Upon contraction, six tail fibers were observed on many particles, four of which appeared to originate from the sheath and two from the inner core. Polysheaths and polycores several hundred nanometers in length were also occasionally observed.

Systematic Discovery of Pseudomonad Genetic Factors Involved in Sensitivity to Tailocins

“…1C). Our micrographs showed an abundance of 20-25nm wide, straight or slightly curved rods, resembling past microscopy reports of Pseudomonas R-tailocins 10,17,31 . Most particles were uncontracted, with lengths between approx.…”

Ribosomally encoded antibacterial proteins and peptides fromPseudomonas

“…The surface of the extended sheath contains different sets of striations, originating from the helically structured six subunit-containing annuli. A baseplate is attached to the sheath and serves as a docking point for the six tail fibers functioning as an anchor for attachment to target cells (Ishii et al, 1965;Higerd et al, 1969;Takeda & Kageyama, 1975). The specific antigens defining target strain specificity are located at the distal portion of the fibers and categorize the pyocins in one of the five classes (R1-R5; Ohsumi et al, 1980;.…”

“…Upon contact, the sheath contracts and the pyocin core is inserted into the cell envelope (Higerd et al, 1969;Govan, 1974a;Shinomiya et al, 1975;Uratani, 1982). The pyocin forms a channel through the inner membrane that causes depolarization of the membrane (Uratani & Hoshino, 1984) and effects arrest of protein and nucleic acid synthesis (Kaziro & Tanaka, 1965;Ohsumi et al, 1980), ultimately resulting in cell death.…”

Production of Bacteriophage-Associated Materials by Vibrio cholerae : Possible Correlation with Pathogenicity

“…1). Higerd et al (9) recently reported a similar phenomenon with pyocin. Our measurements of the particles are in agreement with those of Jayawardene and Farkas-Himsley (11).…”