Basis for the susceptibility of several algae to microbial decomposition.

Partially purified cellulase and a cellulase-containing polygalacturonase but notlysozyme extensively degraded the walls of Chlamydomonas reinhardtii and Ulothrix fimbrata and converted intact cells of the algae to spheroplasts. A streptomycete cellulase cochromatographed with the enzyme system releasing glucose from walls of these organisms, and this preparation also converted the algal cells to spheroplasts. The dominant constituent in the walls was carbohydrate, and glucose and small quantities of galacturonic acid but no amino sugars were present in acid hydrolysates of the walls. Glucose accounted for essentially all of the material solobilized by the cellulase preparation. Lysozyme acted on Cylindrospermum sp. walls, and it, but not the otherenzymes, converted some of the Cylindrospermum sp. cells to spheroplasts. Streptomycete enzymes lysing Micrococcus lysodeikticus cochromatographed with the proteins releasing reducing sugars from Cylindrospermum sp. walls, and components in the active fraction converted cells of this alga into spheroplasts. X-ray diffraction revealed that the walls of C. reinhardtii and U. fimbrata but not those of Cylindrospermum sp. contained cellulose. The data suggest that the susceptibility of the first twospecies to microbial degradation in natural ecosystems results from an attack on the cellulose in their walls, and the susceptibility of the third is linked with the microbial production of a lysozyme.