The effect of bisphenol A on growth, pigment composition and photosystem II activity of Arabidopsis thaliana

Bisphenol A (BPA) is a widely used chemical, that can potentially be toxic to plants. In this study we examined the toxicity of 5-50 mg/l of BPA on Arabidopsis thaliana. Additionally, the effects of 0.5-5 mg/l of BPA were examined after four weeks of development. BPA had no effect on the germination rate and the chlorophyll a/b ratio. The chlorophyll a and carotenoid content was significantly elevated in seedlings treated with 5 mg/l of BPA. In 4-week-old plants there was no change in the chlorophyll and carotenoid content and photosynthetic parameters (Fv/Fm, Fv/F0 and PI) were unaffected, which suggests no photoinhibition. No oxidative stress symptoms were observed. BPA significantly decreased leaf protein content. A low concentration of BPA seems to have no significant effect on A. thaliana flowering, but further investigation is needed. The results obtained indicate that a low concentration of BPA has no negative effect on the growth and development of A. thaliana

The role of antioxidant response and nonphotochemical quenching of chlorophyll fluorescence in long-term adaptation to Cu-induced stress in Chlamydomonas reinhardtii

Copper is an essential micronutrient, but at supraoptimal concentrations it is also highly toxic, inducing oxidative stress and disrupting photosynthesis. The aim of the present study was to analyze selected protective mechanisms in strains of Chlamydomonas reinhardtii adapted and not adapted for growth in the presence of elevated copper concentrations. Two algal lines (tolerant and non-tolerant to high $Cu^{2+}$ concentrations) were used in experiments to study photosynthetic pigment content, peroxidase activity, and non-photochemical quenching. The content of prenyllipids was studied in four different algal lines (two of the same as above and two new ones). The copper-adapted strains contained about 2.6 times more α-tocopherol and plastoquinol and about 1.7 times more total plastoquinone than non-tolerant strains. Exposure to excess copper led to oxidation of the plastoquinone pool in non-tolerant strains, whereas this effect was less pronounced or did not occur in copper-tolerant strains. Peroxidase activity was approximately 1.75 times higher in the tolerant strain than in the non-tolerant one. The increase in peroxidase activity in the tolerant strain was less pronounced when the algae were grown in dim light. In the tolerant line nonphotochemical quenching was induced faster and was usually about 20-30% more efficient than in the non-tolerant line. The improvement of antioxidant defense and photoprotection may be important factors in the evolutionary processes leading to tolerance to heavy metals

Copper excess-induced large reversible and small irreversible adaptations in a population of Chlamydomonas reinhardtii CW15 (Chlorophyta)

Two Chlamydomonas reinhardtii CW15 populations modified by an excess of copper in growth medium were obtained: a “Cu” population that was continuously grown under the selection pressure of 5 µM Cu2+ (for at least 48 weeks) and the “Re” population, where a relatively short (9 week) exposure to elevated copper, necessary for acquiring tolerance, was followed by a prolonged period (at least 39 weeks) of cultivation at a normal (0.25 µM) copper concentration. Cells of the Cu population were able to multiply at a Cu2+ concentration 16 times higher than that of the control population at a normal light intensity and at a Cu2+ concentration 64 times higher when cultivated in dim light. The potential quantum yield of photosystem II (FV/FM ratio) under copper stress was also significantly higher for the Cu population than for Re and control populations. The Re population showed only residual tolerance towards the elevated concentration of copper, which is revealed by an FV/FM ratio slightly higher than in the control population under Cu2+ stress in dim light or in darkness. We postulate that in the Chlamydomonas populations studied in this paper, at least two mechanisms of copper tolerance operate. The first mechanism is maintained during cultivation at a standard copper concentration and seems to be connected with photosynthetic apparatus. This mechanism, however, has only low adaptive value under excess of copper. The other mechanism, with a much higher adaptive value, is probably connected with Cu2+ homeostasis at the cellular level, but is lost during cultivation at a normal copper concentration

A water-soluble [60]fullerene-derivative stimulates chlorophyll accumulation and has no toxic effect on Chlamydomonas reinhardtii

Chlamydomonas reinhardtii (WT 2137) P. A. Dang. (Volvocales, Chlorophyceae) is a green microalgae serving as a suitable model in scientific research and a promising industrial biotechnology platform for production of biofuel, hydrogen and recombinant proteins. Fullerenes (C60) are allotropic carbon nanoparticles discovered in 1985 and used in biomedical studies since the early 1990s, when water solubilization methodologies were developed. Recently, surface-modified hydroxylated derivatives of fullerenes were proven to enhance algal growth and drought tolerance in plants. Here, a novel type of water-soluble [60]fullerene derivative with 12 glycine residues (GF) has been synthesized and tested for acute toxicity (up to 50 μg/ml) and as a potential biostimulant of algal growth. The effects of GF on pigment composition and growth rate of Chlamydomonas reinhardtii were systematically investigated. Our results suggest that GF was not toxic, and no negative change in the pigment content and no stress symptoms were observed. No changes in the photosynthetic parameters based on the fluorescence of chlorophyll a in Photosystem II (NPQ, Fv/Fm, Fv/F0, PI and RC/ABS) were observed. The GF had no effect on cell size and growth rate. At a concentration of 20 μg/ml, GF stimulated chlorophyll accumulation in 3-day-old cultures

Subarachnoid Space: New Tricks by an Old Dog

PURPOSE: The purpose of the study was to: (1) evaluate the subarachnoid space (SAS) width and pial artery pulsation in both hemispheres, and (2) directly compare magnetic resonance imaging (MRI) to near-infrared transillumination/backscattering sounding (NIR-T/BSS) measurements of SAS width changes in healthy volunteers. METHODS: The study was performed on three separate groups of volunteers, consisting in total of 62 subjects (33 women and 29 men) aged from 16 to 39 years. SAS width was assessed by MRI and NIR-T/BSS, and pial artery pulsation by NIR-T/BSS. RESULTS: In NIR-T/BSS, the right frontal SAS was 9.1% wider than the left (p<0.01). The SAS was wider in men (p<0.01), while the pial artery pulsation was higher in women (p<0.01). Correlation and regression analysis of SAS width changes between the back- and abdominal-lying positions measured with MRI and NIRT-B/SS demonstrated high interdependence between both methods (r = 0.81, p<0.001). CONCLUSIONS: NIR-T/BSS and MRI were comparable and gave equivalent modalities for the SAS width change measurements. The SAS width and pial artery pulsation results obtained with NIR-T/BSS are consistent with the MRI data in the literature related to sexual dimorphism and morphological asymmetries between the hemispheres. NIR-T/BSS is a potentially cheap and easy-to-use method for early screening in patients with brain tumours, increased intracranial pressures and other abnormalities. Further studies in patients with intracranial pathologies are warranted

Rozprawa doktorska

PhD thesi

Chlamydomonas and antioxidants

Long-term adaptation to Cu-induced stress in Chlamydomonas reinhardti