DIFFERENTIATION BETWEEN PROTOTHECA AND MORPHOLOGICALLY SIMILAR GREEN-ALGAE IN TISSUE

Abstract

Evidence that algae are pathogens was provided by the results of EM of tissues from 5 cattle and sheep suspected of having green algal infections. Chloroplasts were demonstrated in the algae in each case. Prototheca organisms, considered by some to be achloric mutants of green algae, are causative agents of disease in man and animals and may appear morphologically similar to green algae in tissue. However, EM showed that chloroplasts were absent in these organisms. Light microscopy revealed not only similarities in size, shape and mode of reproduction, but also a striking difference between the Prototheca organisms and green algae. Unlike Prototheca, the green algae contained abundant cytoplasmic starch granules that were strongly positive by several staining procedures; these granules, which were PAS[periodic acid Schiff]-negative following diastase digestion, provide a means of differentiating green algae from Prototheca cells in tissue.