usage of the terms substrate and substratum. A substrate (pI.: substrates) is a material utilized by microorganisms, generally as a source of energy. A substratum (pI.: substrata) is asolid surface to which a microorganism mayattach. REFERENCES (1) Marshall, K.C. 1976. Interfaces in Microbial Ecology. Cambridge, MA: Harvard University Press. (2) ZoBell, C.E. 1943. The effect of solid surfaces upon bacterial activity. J. Bacteriol. 46: 39-56. Standing, left to right: Paul Rutter, Rolf Freter, Mike Silverman, lan Robb, Hinrich Mrozek, Frank Dazzo, David Gingell Seated, left to right: Garth Jones, Stanislawa Tylewska, Staffan Kjelleberg, Ellen Rades-Rohkohl, Kevin Marshall Microbial Adhesion and Aggregation, ed. K.C. Marshall, pp. 5-19. Dahlem Konferenzen 1984. Berlin, Heidelberg, New York, Tokyo: Springer-Verlag. Mechanisms of Adhesion Group Report P.R. Rutter, Rapporteur F.B. Dazzo H. Mrozek R. Freter E. Rades-Rohkohl D. GingeIl I.D. Robb G.W. Jones M. Silverman 8. Kjelleberg 8. Tylewska K.C. Marshall INTRODUCTION The subject, Mechanisms of Microbial Attachment, has proved to be a fertile sour ce of argument between both microbiologists and physical chemists. In order to find common ground for discussion, the group endeavored to come to a consensus regarding a number of definitions pertinent to the subject. Some of these are described in the text and others will be found at the end of this report.

Mechanisms of Adhesion.- Physicochemical Interactions of the Substratum, Microorganisms, and the Fluid Phase.- Stereo-biochemistry and Function of Polymers.- Adhesion to Inanimate Surfaces.- Adhesion to Animal Surfaces.- Bacterial Adhesion to Plant Root Surfaces.- Genetic Control of Bacterial Adhesion.- Biofilm Development and Its Consequences.- Surface Colonization Parameters from Cell Density and Distribution.- Biofilm Development: A Process Analysis.- Chemical Characterization of Films.- Effects of Network Structure on the Phase Transition of Acrylamide-Sodium Acrylate Copolymer Gels.- Colonization by Higher Organisms.- Activity on Surfaces.- Comparative Physiology of Attached and Free-living Bacteria.- Activities of Microorganisms Attached to Living Surfaces.- Utilization of Substrates and Transformation of Solid Substrata.- Attachment of Bacteria: Advantage or Disadvantage for Survival in the Aquatic Environment.- Aggregation.- Physiology of Cell Aggregation: Flocculation by Saccharom yces cerevisiae As a Model System.- Aggregation, Cohesion, Adhesion, Phagocytosis, and Morphogenesis in Dictyostelium - Mechanisms and Implications.- Consequences of Aggregation.- Microcolony Formation and Consortia.- Epilogue.- List of Participants with Fields of Research.- Author Index.