CHARACTERIZATION OF 2 CHLORELLA-VULGARIS (CHLOROPHYCEAE) STRAINS ISOLATED FROM WASTE-WATER OXIDATION PONDS

We report here on the characterization and isolation of two ecotypes o f Chlorella vulgaris Beyerinck that coexist in wastewater reservoirs. One ecotype (C1) contains high amounts of chlorophyll b, is capable of autotrophic growth, and can utilize only a few organic solutes for gr owth. The second ecotype (C2) contains low amounts of chlorophyll b, r equires vitamin B-12, and can support its growth with a broad range of organic compounds. Of the two ecotypes, the latter showed slower grow th rates when light was the sole source of energy. Cells of C2-type Ch lorella attained higher photosynthetic activities than C1-type cells a t saturating irradiances. However, their low chlorophyll b content and lower light utilization efficiency suggest that C2-type Chlorella con tains relatively low amounts of light-harvesting antennae, a disadvant age in severely light-limited ecosystems bike wastewater reservoirs. W e hypothesize that the two Chlorella types coexist by adopting differe nt lifestyles: C1-type cells rely largely on their photosynthetic pote ntial for energy conservation and growth, whereas C2-type cells may ex ploit their heterotrophic properties for this purpose.