Isolation of viable uncontaminated Chlorella from green hydra ’

1979. Effects of food quality on growth of a stream detritivore, Paratendipes albimanus (Meigen) (Diptera: Chi-ronomidae). Ecology 60: 57-64. Abstract-Symbiotic Chlorella isolated from green hydra by simple techniques of homogeni-zation and centrifugation have been found to be contaminated with comparatively large amounts of animal debris. Additional washing with sodium dodecyl sulfate (SDS) removed virtually all contaminating host protein from the Chlorella without affecting its viability. Symbiotic Chlorella lives in intimate association with digestive cells of green hydra. Depending on the strain of hydra, on average lo-25 algae are contained in each digestive cell, and each alga is enclosed by a vacuolar membrane of host origin (Osch-man 1967). Previously, algae have been isolated from green hydra simply by homogenizing animals in hydra medium (M solution: Mus-catine and Lenhoff 1965) to release intact algae and washing the algae by repeated cen-trifugation. However, the algae obtained by this method are contaminated by significant amounts of host material. Mews (1980) showed that about 6% of total maltase activity (an enzyme possessed by the hydra but not by the algae) persisted in the algal fraction after three washes by centrifugation in M, and Douglas and Smith (1983) found that when cultured algae were suspended in homogenates of aposymbiotic hydra proportionate to the normal symbiosis, the al-gal pellet contained 2.5-3 times the original amount of protein after a single centrifu-gation. Contamination of symbiotic algae with host material may lead to serious underestimation of the ratio of host to algal biomass (Douglas and Smith 1983), and contamination of isolated zooxanthellae has been shown to affect measurements of respiration (Tytler and Spencer Davies 1983). The presence of host material may also affect biochemical assays of the algae. Described here is a method modified from that of Meints and Pardy (1980) which provides a suspension of viable algae essentially free of host contamination. I thank L. Mus-catine for laboratory space and equipment and for support and encouragement during the initial stages of this work, D. C. Smith for critical reading of a draft of the manu