. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AMMONIUM METABOLISM IN GREEN HYDRA 1200-] 1000- 800- 600- 215 a) Time (minutes) Figure 2. Effect of MSX, AZS, and ammonium on uptake of [14C]- methylamine by 3N813A algae. Algae were preincubated in 10 mM MES buffer pH 7 for 30 min before addition of 5 pM ['4C]-methylamine to- gether with either 10 pM MSX ( ). 10 nM AZS (O O), 10 nM ammonium chloride (A A), or an equivalent volume of buffer only as control (D D) to give a final density of 5 > 107 cells ml'1. At intervals, 100-^1 samples were filtered and radioactivity was
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AMMONIUM METABOLISM IN GREEN HYDRA 1200-] 1000- 800- 600- 215 a) Time (minutes) Figure 2. Effect of MSX, AZS, and ammonium on uptake of [14C]- methylamine by 3N813A algae. Algae were preincubated in 10 mM MES buffer pH 7 for 30 min before addition of 5 pM ['4C]-methylamine to- gether with either 10 pM MSX ( ). 10 nM AZS (O O), 10 nM ammonium chloride (A A), or an equivalent volume of buffer only as control (D D) to give a final density of 5 > 107 cells ml'1. At intervals, 100-^1 samples were filtered and radioactivity was determined. no effect on glutamine and glutamate pools or on the Gin: Glu ratio of the algae (Table I), the latter being an indicator of nitrogen sufficiency in microalgae (Flynn ci 1989). In marine symbioses. in which it is believed that symbionts are able to assimilate ammonium from seawater, am- monium supplementation not only causes large increases in the population density of symbionts (Muscatine et ai, 1989; Hoegh-Guldberg and Smith. 1989; Dubinsky et a!.. 1990; Fitt and Cook, 1990; Stambler et «/.. 1991; Muller- Parker et ai. 1994). but. in a coral and a hydroid, also increases the size of internal glutamine pools of symbionts and hence their Gln:Glu ratio (McAuley, 1994; McAuley and Cook, 1994). Further, although MSX inhibits ammonium uptake by intact hydra (Rees, 1986; McAuley. 1990; Table II. this paper), almost no MSX was detected in symbiotic algae isolated from hydra that had been incubated in MSX for 24 h, and there was no change in algal internal pools of glutamate and glutamine. In contrast, freshly isolated symbionts treated with MSX rapidly accumulated large amounts of the inhibitor, and MSX treatment caused predictable changes in glutamate and glutamine pools of freshly isolated symbionts and cultured 3N813A algae in a variety of conditions (Tables III and IV). o T3 '0 O 03 "o. Time (minutes) Figure 3. Effect of glutamine uptake on internal pools
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