The Leeuwenhoek Lecture, 1967 - Teichoic acids and the molecular structure of bacterial walls

Abstract

A glance at previous Leeuwenhoek Lectures reveals that in a number of cases the Lecturer has felt obliged to preface his account with an apology to the effect that the subject of his lecture would seem to bear little relationship to the distinguished work of Antony van Leeuwenhoek. In my case, however, such apology is unnecessary as a reasonably direct connexion can be established between those remarkable observations in the seventeenth century and the work described here. Leeuwenhoek’s description of bacteria is based on their appearance under his primitive but remarkably effective microscopes. Such appearance is, of course, governed by shape and we see from the published record that cocci, bacilli and spirochaetes were observed and accurately described in terms of size and shape. These features are functions of the nature and rigidity of the wall surrounding the organisms and so are related to molecular structure; the purpose of my lecture is to describe certain aspects of the recently acquired knowledge of the molecular architecture of bacterial cell walls. The great interest that has developed in the chemistry and biochemistry of bacterial cell walls during the last ten years or so has arisen for a number of reasons (cf. Salton 1964). In the first place, walls are of interest because they represent a substantial proportion of the metabolic products of the cell; they frequently comprise up to 20% of the dry weight of cells and so must be regarded as important metabolites. Moreover, their chemical structure is interesting in view of their physical properties. Thus, besides being reasonably rigid structures with considerable strength they are nevertheless freely permeable towards cellular products and nutrients. Under certain conditions even large molecules such as antibodies, extracellular enzymes and nucleic acids can penetrate the wall, although the full extent and nature of this permeability, and the effect of negatively charged polymers (e. g. teichoic acids) in the wall, has not been clearly defined. The wall is frequently the site of important antigenic material; for example, in many cases it has been shown, that group- or type-specific antigens are located in the outer structures of the cell, including the wall. Consequently, a better understanding of the immunological properties of bacteria, and particularly such features as patho-genicity, require a full understanding of the structure, function and biosynthesis of wall components.