Cell cycle dependent expression of toxicity by the ichthyotoxic prymnesiophyte Chrysochromulina polylepis

Abstract

The coupling of toxicity expression with cell-cycle phases was studied in the toxic marine prymnesiophyte Chrysochromulina polylepis Manton & Parke, Clone B1511. Cell synchronisation of cultures in exponential or early stationary growth phases under nutrient-replete conditions was achieved by manipulation of the photoperiod. Chlorophyll a (chl a) and cell number increased in a stepwise manner, but were asynchronous, with chl a increasing during the light period and cell number increasing during the dark period. In the course of the light period, nearly all cells clustered in the G1 (Gap 1) phase, which lasted for about 20 h. DNA synthesis (S phase) occurred mainly in the dark during a discrete period (about 4 h) and G2 (Gap 2) and mitosis (M) were always completed before the end of the dark period. Toxicity expression, measured by the erythrocyte lysis assay (ELA), exhibited a dramatic drop in LC 50 values (increase in toxicity) during the light period, although this effect was less pronounced after the first 2 generations of cell division when the cultures had entered the stationary phase. Similarly, haemolytic activity per unit cell volume decreased by a factor of 3 to 4 during the dark period over the first 48 h, but became irregular towards the end of the experiment. In this study, the light-dependent effect on toxicity and relationship to discrete phases of the cell cycle are demonstrated for the first time in a prymnesiophyte. KEY WORDS: Cell cycle · Ichthyotoxins ·Phytoflagellates ·Prymnesiophytes ·Chrysochromulina polylepis Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 39: [85][86][87][88][89][90][91][92][93][94][95] 2005 Paasche 1998 [review], Johnsen et al. 1999). The definitive causes of these blooms remain unknown, but in addition to meteorological, hydrographical and chemical conditions that promote growth and toxin production in Chrysochromulina spp., adverse effects on planktonic grazers may also have played a role in bloom development (Nielsen et al. 1990, John et al. 2002.The chemical characterisation of Chrysochromulina polylepis toxin(s) is still lacking. The mode of action of these toxins is apparently non-selective, causing interference mainly with membrane functions, and thus organisms ranging from protozoans to fish are known to be affected (Skjoldal & Dundas 1991, Gjø-saeter et al. 2000. Yasumoto et al. (1990) described the toxins as glucolipids and/or fatty acids, but John et al. (2002) showed that a toxic and an apparently non-toxic clone of C. polylepis exhibited the same lipid and fatty acid composition.Curiously, prior to the major ichthytoxic event in Scandinavia, Chrysochromulina polylepis had been considered to be non-toxic to fish (Manton & Parke 1962) and only slightly toxic to a bryozoan, Electra pilosa (Jebram 1980). Toxicity of C. polylepis was demonstrated to be highly variable within and among strains of this species (review by Edvardsen & Paasche 1998). Little is known of the factors triggering toxicity, but un...

Hemolytic toxicity and nutritional status of Prymnesium parvum during population growth

“…Daily cycles in hemolytic toxicity occur in the closely related haptophyte species Chrysochromulina polylepis (Eschbach et al 2005). Peaks in the magnitude of toxicity occurred late in the dark phase of the photoperiod, coinciding with the S-phase of the cell cycle (Eschbach et al 2005). In contrast, cycles with periods of several days were observed for Prymnesium parvum cultures in the present study and by Uronen et al (2005).…”

“…Eschbach et al culture. It is possible that daily cycles of toxicity occurred, but were missed in studies with daily or less frequent sampling, and that longer period cycles would have been observed by Eschbach et al (2005) had their observations continued.…”

“…Daily cycles in hemolytic toxicity occur in the closely related haptophyte species Chrysochromulina polylepis (Eschbach et al 2005). Peaks in the magnitude of toxicity occurred late in the dark phase of the photoperiod, coinciding with the S-phase of the cell cycle (Eschbach et al 2005).…”

“…Eschbach et al culture. It is possible that daily cycles of toxicity occurred, but were missed in studies with daily or less frequent sampling, and that longer period cycles would have been observed by Eschbach et al (2005) had their observations continued.Except for pH, none of the properties measured here differed significantly among standard, buffered, and aerated cultures. Although pH was from 0.5 to 2 units higher in buffered cultures than in other treatments, toxicity did not differ.…”

Transcriptomic response of the toxic prymnesiophyte Prymnesium parvum (N. Carter) to phosphorus and nitrogen starvation

“…Only cultures without evidence of bacteria were used as inoculum. Experimental cultures were grown under standard conditions as stated above in 5 l screw-cap glass bottles under gentle aeration and were sampled with a sterile tube-vacuum system (Eschbach et al, 2005).…”