Chrysophyte Poterioochromonas Malhamensis Research Articles

Occurrence of the Freshwater Chrysophyte Poterioochromonas malhamensis in a High Arctic Marine Ecosystem

Kongsfjorden is a small Arctic fjord but with great hydrographic complexity and has changed greatly due to the climate change. Arctic warming has increased melts of sea ice and glaciers that results in higher freshwater content. Microbial community variability and increasing terrestrial input were detected continuously in recent years ITag eukaryotic 18S rRNA V4 metabarcoding, photosynthetic pigments analysis and epifluorescence microscopy were used to reveal the dominant species of small eukaryotic community (<20 μm). Both Spearman correlation and redundant analysis were used to study the correlation between the small eukaryotes and the environmental conditions. In the present study, the surface water with salinity lower than 34 was thicker than in summers of previous years. The freshwater mixotrophic chrysophyte Poterioochromonas malhamensis was found for the first time as the dominant species. No general trends were found for the contributions of P. malhamensis to the total reads of small eukaryotes in water depths; and no obvious differences were found at different stations and water masses. Phagotrophy, which is more common than phototrophy at all times in P. malhamensis, is thought to be the main reason for the prevalence of P. malhamensis in Kongsfjorden. The occurrence of P. malhamensis induced a disorder in the small eukaryotic community, which biodiversity and composition showed weak correlation with the water masses. The dominance of the freshwater-originating phytoplankton may indicate an ecosystem change in the Kongsjforden, which probably might become more remarkable in the future as the climate continues to change.

Quantitative Proteomics Reveals Ecophysiological Effects of Light and Silver Stress on the Mixotrophic Protist Poterioochromonas malhamensis.

Aquatic environments are heavily impacted by human activities including climate warming and the introduction of xenobiotics. Due to the application of silver nanoparticles as bactericidal agent the introduction of silver into the environment strongly has increased during the past years. Silver ions affect the primary metabolism of algae, in particular photosynthesis. Mixotrophic algae are an interesting test case as they do not exclusively rely on photosynthesis which may attenuate the harmful effect of silver. In order to study the effect of silver ions on mixotrophs, cultures of the chrysophyte Poterioochromonas malhamensis were treated in a replicate design in light and darkness with silver nitrate at a sub-lethal concentration. At five time points samples were taken for the identification and quantitation of proteins by mass spectrometry. In our analysis, relative quantitative protein mass spectrometry has shown to be a useful tool for functional analyses in conjunction with transcriptome reference sequences. A total of 3,952 proteins in 63 samples were identified and quantified, mapping to 4,829 transcripts of the sequenced and assembled transcriptome. Among them, 720 and 104 proteins performing various cellular functions were differentially expressed after eight days in light versus darkness and after three days of silver treatment, respectively. Specifically pathways of the energy and primary carbon metabolism were differentially affected by light and the utilization of expensive reactions hints to an energy surplus of P. malhamensis under light conditions. The excess energy is not invested in growth, but in the synthesis of storage metabolites. The effects of silver were less explicit, observable especially in the dark treatments where the light effect could not mask coinciding but weaker effects of silver. Photosynthesis, particularly the light harvesting complexes, and several sulphur containing enzymes were affected presumably due to a direct interference with the silver ions, mainly affecting energy supply.

Toxicity of the mixotrophic chrysophyte Poterioochromonas malhamensis to the cladoceran Daphnia ambigua

The toxicity of the mixotrophic chrysophyte Poterioochromonas malhamensis to the common cladoceran Daphnia ambigua was investigated with laboratory survivorship experiments and observations of feeding behavior. When cultured autotrophically in an inorganic medium, P. malhamensis provided sufficient nutrition for survival and reproduction by D. ambigua. However, P. malhamensis grown heterotrophically on an organic medium (osmotrophically) in the dark or light was toxic to D. ambigua, killing all experimental animals within five days. Toxicity was not caused by the organic medium since daphnids fed the autotroph Chlamydomonas reinhardi that was grown in the organic medium had high survivorship. Changes in feeding behavior supported the results from the survival studies. Daphnids feeding in suspensions of heterotrophically cultured P. malhamensis exhibited significantly greater food rejection rates than animals fed autotrophically cultured P. malhamensis or C. reinhardi. Differences in the growth rate or biochemical pathways of heterotrophically versus autotrophically grown P. malhamensis likely influenced toxin production. Poterioochromonas may affect zooplankton feeding and behavior in nature if heterotrophic toxin production is comparable between phagotrophic and osmotrophic nutritional modes.

Colloidal and Dissolved Organic Matter Excreted by a Mixotrophic Flagellate during Bacterivory and Autotrophy

Excretion of dissolved and colloidal organic carbon by a mixotrophic flagellate, the chrysophyte Poterioochromonas malhamensis, was studied. Flagellates were incubated either with C-labeled bacteria or with inorganic C, in order to compare organic exudates originating from primary production with exudates originating from ingested bacteria. Colloids of >0.02 mum constituted a larger fraction of the exudates originating from ingested bacteria, compared with exudates derived from primary production. Flagellate feeding on bacteria specifically labeled in different cell components was compared. Cell wall components gave rise to less colloidal organic carbon than did other cell constituents. To investigate the degradability of flagellate C-exudates, they were added to lake water and mineralization to CO(2) was monitored. Bacterially derived exudates were more recalcitrant than exudates originating from photosynthesis. The results support the hypothesis that bacterial utilization of labile organic compounds, followed by flagellate bacterivory and exudation, results in a transformation of labile organic matter into more recalcitrant forms.

Structure of malhamensilipin A, an inhibitor of protein tyrosine kinase, from the cultured chrysophyte Poterioochromonas malhamensis.

A new chlorosulfolipid, malhamensilpin A [1] was isolated from the cultured chrysophyte Poterioochromonas malhamensis. Malhamensilipin A was demonstrated to be a modest inhibitor of pp60v-src protein tyrosine kinase. The structure was determined by detailed spectral analysis to be a novel C24 hexachloro lipid containing a vinyl sulfate ester (2,11,12,13,15,16-hexachloro-14-hydroxy-n-tetracos-1E-enol-1-sulfa te).

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: VII. Protective action of thiol compounds, vitamins, trace elements, and other agents

The influence of 45 different substances on the growth inhibiting effects of triethyl lead chloride (TriEL) in cultures of the unicellular alga Poterioochromonas malhamensis was studied. Ten thiol or disulfide compounds, 9 vitamins, 12 trace elements, 14 miscellaneous agents, and 9 combinations of these agents were tested. The agents were applied to the algal cultures in three different concentrations simultaneously with 10 μ M TriEL and incubated for 72 hr. While none of the tested thiol and disulfide compounds remarkably protected the algae from TriEL toxicity, two vitamins (tocopheryl acetate, ascorbic acid), one trace element (zinc), adenosine-5′-triphosphate Na 2 salt, cyclic AMP, and concanavalin A as well as combinations of some of these agents were found to suppress markedly the growth inhibiting effects of TriEL. Zinc was the most effective agent; it increased algal growth in TriEL-treated cultures by about 70 times as compared with cultures containing TriEL alone. A combination of 10 essential trace elements was even more protective and almost completely suppressed TriEL toxicity. In contrast to this, some of the other agents potentiated the toxic effects of TriEL (e.g., magnesium, molybdenum, caffeine, deuteriumoxide, chlorpromazine, dimethylsulfoxide) in the tested concentration ranges. The most protective agents Zn, VitC, and VitE did not prevent the inhibitory effects of TriEL on microtubule (MT) assembly in vitro, suggesting that their in vivo protection is based on mechanisms other than direct protecting MTs from the attack of the lead compound. Zn had no direct influence on the stability and half life of TriEL in the growth medium. The lack of protection found by the thiol compounds used suggests that most probably general thiol interaction of TriEL is not its major toxic mechanism of action. It is postulated that the protective action of Zn, VitE, and VitC is directly or indirectly mediated by suppression of TriEL-induced peroxidation processes in the poisoned algae. The protective agents found provide a basis for further screening experiments in order to test their “therapeutic” potency in experimental animals poisoned with organolead.

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: VI. Effects on lorica formation, mitosis, and cytokinesis

Effects of tetraethyl lead (TEL) and derivatives triethyl lead (TriEL), diethyl lead (DiEL), and inorganic lead (Pb) on lorica formation of the unicellular alga Poterioochromonas malhamensis were investigated by light and electron microscopy. Lorica formation is microtubule (MT)--mediated and disturbed by agents interfering with MTs. TEL, largely ineffective as such, inhibited lorica formation of P. malhamensis when the lead compound was illuminated during or before the experiment. TriEL inhibited most; DiEL produced qualitatively effects similar to those of TriEL at about 10 times higher concentrations. Inorganic lead was even less toxic and did not selectively inhibit lorica formation of the algae. Low concentrations of TriEL (5 to 7.5 microM) selectively disturbed lorica formation, causing formation of numerous stalk-less loricae which exhibited gross and ultrastructural alterations like those induced by the antimitotic drug colchicine. The effects of TriEL on mitosis and cytokinesis of P. malhamensis were also investigated. The most sensitive mitotic phase was metaphase, which, however, accumulated only up to 5% after treatment of the cells with toxic concentrations (10 microM) of TriEL for 24 hr (control, 2%). On the other hand, up to 15% telophases (including binucleated cells) and even multinucleated cells with up to eight nuclei per cell were found, indicating that cytokinesis was considerably more effectively disturbed by TriEL than mitosis. In giant multinucleated algae, mitoses normally proceeded synchronously; some asynchronous mitoses were found. Beside normal-looking mitotic spindles in giant algae, multipolar spindles, disoriented spindles, and metaphase-like chromosome arrays completely lacking MTs were observed by electron microscopy. The effects of TriEL on cytokinesis of the algae were largely reversible. Giant cells spontaneously recovered and underwent cytokinesis after transferred into TriEL-free growth medium. Colchicine acted qualitatively identical to TriEL (accumulation of metaphases and telophases: 5 and 19%, respectively), but TriEL was about 600 times more toxic than colchicine. Unlike colchicine, its derivative, colchicine, which is known not to interfere with MTs, remained without any selective inhibitory influence on mitosis and cytokinesis of the algae, although much more toxic than the parent compound. From the inhibitory effects of TriEL and the close qualitative similarities to the effects of colchicine, it is concluded that TriEL selectively interferes with cytoplasmic and mitotic MTs of the algae, thereby causing the observed inhibitory effects on lorica formation, mitosis, and cytokinesis.

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis—V. Electron microscopical studies

The unicellular alga Poterioochromonas malhamensis was treated for 2–7 days with toxic concentrations of lead nitrate (Pb, 1000 μM), triethyl lead (TriEL, 10 μM) and tetraethyl lead (TEL, 100 μM) and examined by transmission electron microscopy. 1000 μM Pb caused deformations of nuclei, structural alterations of mitochondria and an increase of autolytic activity. Both organic lead compounds were considerably more toxic than inorganic lead and the resultant ultrastructural alterations were highly complex, generally involving all cell organelles. The most prominent ultrastructural effects of organolead were an increase in the number and/or size of nuclei, contractile vacuoles, chloroplasts and dictyosomes. A marked accumulation of lipid droplets and of lysosomes was observed as well as the occurrence of (lipofuscin-like) residual bodies. Mitochondria were not remarkably affected. Basal body complexes consisting of up to four basal bodies without visible contacts to the cell membrane or to flagellae were found in the cytoplasm of giant cells. The described toxic effects of TEL and TriEL in P. malhamensis closely resemble the structural damages caused by organolead in other plant organisms or in tissues of experimental animals.

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte poterioochromonas malhamensis. IV. influence of lead antidotes and related agents

The unicellular alga Poterioochromonas malhamensis was exposed to 12.5 μM of inorganic or triethyl lead and simultaneously treated with lead antidotes and related agents at concentrations of 12.5, 31.25 and 62.5 μM. With increasing concentrations some of the antidotes alone slightly to severely inhibited algal growth (BAL ∗, CaNa 2EDTA, EDTA, Na 2EDTA), whereas others (DPA, EGTA, DIZO) were non-toxic at the concentrations tested. EGTA and CaNa 2EDTA, at all concentrations tested, completely suppressed the growth inhibition caused by inorganic lead; Na 2EDTA and EDTA were protective at the lower or medium concentrations, but DIZO. DPA and BAL considerably enhanced lead toxicity with increasing concentrations. None of the tested agents was able to reduce the toxic effects of triethyl lead. All antidotes markedly increased inhibition of algal growth caused by triethyl lead and some were even lethal to the poisoned algae either at the highest (Na 2EDTA, EDTA, DPA) or at all concentrations used (DIZO, BAL). P. malhamensis proved to be a highly sensitive and valuable tests system and the results obtained exhibited striking parallels to medical and clinical experience in therapy of human poisoning with inorganic and organic lead compounds.

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: II. Triethyl lead, diethyl lead, and inorganic lead

The toxic effects of the tetraethyl lead (TEL) derivatives triethyl lead (TriEL), diethyl lead (DiEL), and of inorganic lead (Pb 2+) on the Chrysophyte Poterioochromonas malhamensis were studied. The algae's parameters of interest were cell growth, and the formation of giant cells and of polyploid nuclei. (1) Based on their zero-growth-inducing concentrations, the tested lead compounds reveal the following relative toxicities to the algae: Pb 2+, light/darkness = 1 1 ; DiEL, light/darkness = 11 10 ; TriEL, light/darkness = 55 33 ; TEL, light/darkness = 7 0 . (2) The lead compounds differ greatly in the concentration ranges which cause slight inhibitory to lethal effects. The ranges are: Pb 2+ = 5 to >1000 μ m (>200×); DiEL = 5 to 100 μ m (20×); TriEL = 5 to 25 μ m (5×). (3) Pb 2+ is the least toxic TEL derivative. Its growth-inhibiting effect is remarkably high at very low concentrations (10μ m) but it increases only slightly with rising concentrations. Even 3-day treatment with 1000 μ m Pb 2+ is not lethal to the whole culture. Between 10 to 500 μ m Pb 2+, the nuclear indices of the cultures stay nearly unaffected, whereas there is a moderate but distinct increase in the percentage of polyploids, with maxima of 10% in the light and 6% in darkness. (4) DiEL is about ten times more toxic to Poterioochromonas than Pb 2+. It inhibits cellular growth and leads to the formation of giant cells and of polyploid nuclei under light and dark conditions. DiEL is much less stable to light than TriEL. In the course of the experiments it obviously tends to decompose upon illumination to a less active and less water-soluble compound. (5) Among the tested TEL derivatives, TriEL is the most toxic. In light as well as in darkness it inhibits algal growth and leads to the formation of giant multinucleated cells and of polyploid nuclei. The effects of TriEL are identical to those which were observed in TEL-treated illuminated cultures of Poterioochromonas. (6) Although DiEL has TriEL-like activity, there is evidence suggesting that in these experiments DiEL is not formed from TEL in critical amounts. The present studies further support the idea that TriEL is the primary derivative of TEL in illuminated algal cultures and that TriEL is the agent which causes the severe inhibitory effects in TEL toxicity to Poterioochromonas malhamensis.

On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: I. Tetraethyl lead

The influence of illumination and aeration on the behavior of the antiknock additive tetraethyl lead (TEL) in aqueous media and on its toxicity to cultures of Poterioochromonas malhamensis was studied. Based on the results of these investigations the following conclusions were drawn: (i) In darkness TEL is not toxic to the algae, even at extremely high concentrations. (ii) Depending on TEL concentration, the growth, mitosis, and cytokinesis of the cells are inhibited in illuminated cultures, resulting in the formation of giant cells. (iii) TEL is converted to a highly toxic derivative by light in the presence as well as in the absence of living cells. Therefore it is concluded that Poterioochromonas is not able to metabolize TEL to the toxic agent. (iv) The photolytic toxification of TEL can be detected after as little as 3 to 6 hr of incubation in the light. Maximal toxicity is reached after 24 to 32 hr of illumination. (v) Free radicals, which can be formed by photolysis of TEL, seem to play no or only a minor role in TEL toxicity to Poterioochromonas. (vi) Due to its low water solubility and its high air solubility and volatility, TEL is cleansed from the cultivation media by aeration. This process seems to be completed after 2 to 3 days of aeration in darkness. In the light, however, this process is counteracted by the photolytic creation of a more stable, water-soluble, and nonvolatile TEL derivative which accumulates with time and which is responsible for the toxic effects. (vii) Very probably this toxic TEL derivative is identical to triethyl lead.