Form and function of the glycocalyx on free cell surfaces

Abstract

Selected examples of the glycocalyx or cell coat on rickettsiae, bacteria, amoebae, sea-urchin eggs and the cat intestinal microvilli are illustrated and their functional roles are discussed. The differences in the form of various surface coats are noted; while many surface components are truely extraneous expendable coatings, others are so firmly attached that they seem to be a permanent part of the cell. The fuzzy surface coat on the cat intestinal microvilli have been considered in some detail and some new observations on the form of the glycocalyx are presented. The enteric surface coat is not readily visualized in fractured surface replicas of glycerinated tissue but fixed cells frozen in distilled water when replicated after freeze-etching reveal a flamboyant array of a filamentous meshwork attached to the microvilli. This fuzzy coat layer is at least twice as thick in the freeze-etched preparations when compared to thin sectioned material. Fresh tissue frozen without fixation or glycerin treatment did not have a thick fuzzy coat. In its place a thin amorphous blanket-like layer was found.