Gliding motility of Cytophaga sp. strain U67

Abstract

Video techniques were used to analyze the motion of the gliding bacterium Cytophaga sp. strain U67. Cells moved singly on glass along the long axis at a speed of about 2 micrometers/s, advancing, retreating, stopping, pivoting about a pole, or flipping over. They did not flex or roll. Cells of different lengths moved at about the same speed. Cells sometimes spun continuously about a pole at a frequency of about 2 HZ, the body moving in a plane parallel to that of the glass or on the surface of a cone having either a large or a small solid angle. Polystyrene latex spheres moved to and fro on the surfaces of cells, also at a speed of about 2 micrometers/s. They moved in the same fashion whether a cell was in suspension, gliding, or at rest on the glass. Two spheres on the same cell often moved in opposite directions, passing by one another in close proximity. Small and large spheres and aggregates of spheres all moved at about the same speed. An aggregate moved down the side of a cell with a fixed orientation, even when only one sphere was in contact with the cell. Spheres occasionally left one cell and were picked up by another. Cell pretreated with small spheres did not adhere to glass. When the cells were deprived of oxygen, they stopped gliding, and the spheres stopped moving on their surfaces. The spheres became completely immobilized; they no longer moved from cell to cell or exhibited Brownian movement. Cytophaga spp. are known to have a typical gram-negative cell envelope: an inner (cytoplasmic) membrane, a thin peptidoglycan layer, and an outer (lipopolysaccharide) membrane. Our data are consistent with a model for gliding in which sites to which glass and polystyrene strongly adsorb move within the fluid outer membrane along tracks fixed to the rigid peptidoglycan framework.