The present volume is the first attempt to bring together, in a comprehensive and comparative manner, the vast knowledge accumulated on the mycoplasma cell membranes. The state-of-the-art coverage includes physical studies of lipid organization and dynamics in mycoplasma membranes, the role of cholesterol in mycoplasma membranes, spiralins, and eight other subjects.

The mycoplasmas, a trivial name used to denote organisms included in the class Mollicutes, are a group of prokaryotic organisms comprising more than 120 species distinguished from ordinary bacteria by their small size and the total lack of cell walls. The absence of a cell wall in mycoplasmas is a characteristic of outstanding importance to which the mycoplasmas owe many of their pecu liarities, for example, their morphological instability, osmotic sensitivity, unique ion pumping systems, resistance to antibiotics that interfere with cell wall bio synthesis, and susceptibility to lysis by detergents and alcohols. The fact that the mycoplasma cells contain only one membrane type, the plasma membrane, constitutes one of their most useful properties for membrane studies; once the membrane is isolated, it is uncontaminated with other mem brane types. Another advantage in using mycoplasmas as models for membrane studies stems from the fact that their membrane lipid composition can be altered in a controlled manner. This characteristic results from the partial or total inabili ty of the mycoplasmas to synthesize long-chain fatty acids and cholesterol, making mycoplasmas dependent on the supply of fatty acids from the growth medium. The ability to introduce controlled alterations in the fatty acid composi tion and cholesterol content of mycoplasma membranes has been utilized in studying the molecular organization and physical properties of biological mem branes.

The meeting on "Microbial Surface Components and Toxins in Relation to Pathogenesis" was held on May 15-19, 1989, in the Mitzpe Rachel guesthouse of Kibbutz Ramat Rachel in Israel. Four major topics formed the basis for the meeting: adhesion and colonization; cell invasion and intracellular multipli cation; evasion of host defenses; toxins and systemic effects. The presentations clearly show that our understanding of the pathology, pathogenesis and bacteria-host cell inter-action has greatly advanced over the last few years. The contributions to our knowledge on the biogenesis of adhesins and their molecular organization, as well as on the mechanism of adherence to infected target tissue by pathogenic bacteria, have been particularly impressive. significant progress has been made in defining the nature of pathogenic and cytotoxic factors produced by bacteria, and much has been learned about the biochemical and antigenic modifications occurring in diverse types of host cells upon infection. The discussions of poly saccharide capsules, bacterial endotoxins and secreted toxins illustrated the challenge and the possibilities for vaccine development."