Growth of Micro-organisms in Gel-stabilized Two-dimensional Diffusion Gradient Systems

Department of Microbiology, University College, Newport Road, Cardiff CF2 ITA. UK ABSTRACT SUMMARY: The Szybalski wedge plate technique was modified to generate two-dimensional diffusion gradients for two environmental variables: pH value and NaCl concentration were selected in this study. After experimentation, pH values chosen ranged from 3.9 to 8.1 and salt concentrations from 23 to 79 gl -1 . The pH gradients were slightly sigmoidal whilst the salt gradients were approximately linear. The reproducibility of the technique was assessed and found to be satisfactory in replicate growth experiments. A wide range of growth patterns was observed for a large variety of different bacterial types. The growth boundary and the pattern details are sufficiently distinct to suggest that the technique can distinguish between closely related species or strains.