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Catherine Legrand 1, Geir Johnsen 2, Edna Granéli 1, Egil Sakshaug 2 1Dept. of Marine Sciences, University of Kalmar, Box 905, S-391 29 Kalmar, Sweden 2Trondhjem Biological Station, Norwegian University of Sciences and Technology, Bynesvn 46, N - 7491 Trondheim, Norway
The influence of the polyamines (putrescine and cadaverine) were tested on non-axenic cultures of ichthyotoxic algae Chrysochromulina leadbeateri (CLTJ1) and Prymnesium patelliferum. Replicate cultures of exponentially growing cells were incubated with or without polyamines under light and temperature controlled conditions. Cell abundance, toxicity (haemolytic and Artemia salina assays) were analysed, and behaviour (swimming, cannibalism, phagotrophy) was recorded after 24 and 48h. Addition of putrescine and/or cadaverine (1-110 µM) to the culture medium stimulated growth and resulted in increased cell numbers in C. leadbeateri and P. patelliferum (putrescine: + 30-50 %, cadaverine: 0-30%). High concentrations of both polyamines (1100 µM) had a negative effect on cell numbers in P. patelliferum (no increase) and in C. leadbeateri (i.e. up to 90-100 % lysed cells relative to the control cultures). Haemolytic substances were extracted both from the cells and the culture medium. Within the range 0-11µM of putrescine addition, C. leadbeateri showed very low haemolytic activity (< 1 Seq µg ml-1). At high concentrations of putrescine (110 and 1100 µM), the haemolytic activity increased up to 10 Seq µg ml-1 in the particulate fraction after 48 h. Additions of putrescine, cadaverine or both polyamines gave similar effects on the haemolytic activity in P. patelliferum. Furthermore, the toxicity of P. patelliferum towards A. salina was enhanced four times at 1100 µM polyamines. Chrysochromulina leadbeateri was not found toxic to A. salina. Addition of polyamines (> 110 µM) resulted in erratic swimming behavior, hyperactivity of the cells for both species, and a significant increase (0 to 10 % of the population) of cannibalism occurred in P. patelliferum cultures. Our results support the hypotheses that (i) polyamines may act as growth enhancing compounds, (ii) the haemolytic/ichthyotoxic substances produced by C. leadbeateri/ P. patelliferum and the polyamines (added or derived from bacterial decomposition) may produce a haemolytic-polyamine complexes that could be stable in a colloidal phase and possibly "hypertoxic", (iii) polyamines may favour the mixotrophic growth of C. leadbeateri/P. patelliferum.
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