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...