Observations of the Effects of Membrane Grid Lines on the Growth of Bacterial and Yeast Colonies. Yishan Lin, J. E. Siebel Sons' Company, Enzyme Products Division, Miles Laboratories, Inc., Chicago, IL 60646. J. Am. Soc. Brew. Chem. 38:0079, 1980.

Laboratory observations have indicated that the grid lines on the surface of membrane filters restrict the growth of bacterial and yeast colonies, causing the colonies to become irregular in shape. Various species of microoganisms as well as different brands of membrane filter varied in amounts of restriction. Among the gridded membrane filters tested, white-Millipore and black-Millipore exerted the greatest restricting effects, whereas the grid lines of white-Gelman, green-Gelman, and Nuclepore membranes had the least effect. Yeast isolates containing mycelial growth were more resistant to grid line restriction than were those lacking mycelium. The amount of agar in the culture media also had a marked influence on the response of microorganisms to grid lines.

Keywords: Agar content, Colony shape, Membrane filter