The effect of temperature on growth and production of paralytic shellfish poisoning toxins by the cyanobacterium Cylindrospermopsis raciborskii C10

Abstract

Cylindrospermopsis raciborskii is a cyanobacterium which produces either cylindrospermopsine or paralytic shellfish poisoning (PSP) toxins. We studied the effect of temperature on growth and production of PSP toxins by C. raciborskii C10, isolated from a freshwater reservoir in Brazil. We analyzed the extracellular and intracellular content of PSP toxins at two different temperatures: 19 and 25 °C. C. raciborskii C10 produces STX, GTX2, and GTX3 at both temperatures. dcSTX was also detected at 25 °C in the intracellular extracts obtained at the end of the stationary phase. The growth achieved at 25 °C and estimated by optical density at 700 nm was three times greater than at 19 °C. However, no significant differences were observed in the content of PSP toxins in either the cells or the extracellular media. The kinetics of accumulation of PSP toxins within the cells rather than in the media suggests an active PSP toxins-export process that is not related to cell lysis. The extracellular accumulation of PSP toxins at 19 °C suggested a biotransformation of STX to the epimers GTX2 and GTX3. The stability of the PSP toxins produced by C. raciborskii C10 was high enough for them to remain active in the media after 30 days (at 25 °C) or after 50 days (at 19 °C).