GROWTH-PATTERNS OF SACCHAROMYCES-CEREVISIAE MICROCOLONIES IN ALGINATEAND CARRAGEENAN GEL PARTICLES - EFFECT OF PHYSICAL AND CHEMICAL-PROPERTIES OF GELS

When Saccharomyces cerevisiae cells were inoculated at low density (1 . 10(3)-1.5 . 10(5) cells [g gel](-1)] in alginate gel beads and cylin ders, cells grew in the form of distinct microcolonies throughout the gel matrix. Alginate gel bends and cylinders, formed by external gelat ion with Ca2+, gave rise to microcolonies which became elongated and l ens-shaped with their major axes aligned with the gel surface. The asp ect ratio (major axis/minor axis length) of the microcolonies and the local concentration of alginate increased with increasing distance fro m the center of the gel particles. In contrast, spherical microcolonie s were observed in alginate cylinders formed by internal gelation and no significant local concentration gradients of alginate were detected in these gels. Nonspherical microcolonies were also observed in carra geenan gel bends. However, the colonies were irregularly shaped, and t heir major awes demonstrated no preferential alignment.