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    Bioavailability of different iron amounts and speciations and EDTA-iron complexes for Emiliania huxleyi (Prymnesiophyceae)
    (Parlar Scientific Publications (P S P), 2007) Isik, Oya; Sayin, Selin; Hizarci, Leyla; Ozturk, Murat
    The purpose of this study was to determine the effects of daily and/or initial additions of varying Fe(II) and Fe(III) amounts, in combination with or without EDTA, on Emiliania huxleyi cultures. Pertaining to this specific aim, the growth rate (mu), cell abundance (X10(4) cells L-1), total chi a concentration ([tg L-1), chi a quota (pg cell-'), chi a:C ratio, Fe content (amol cell(-1)), Fe:C and Fe:chl a (pmol:ng) ratios, as well as pH values were observed. During the experiment, iron-free seawater was obtained by using a Chelex-100 column for iron-cleaning. The results revealed that the cell densities, growth rates, chlorophyll a concentrations, Fe contents, the calculated Fe:C ratios, and pH values were higher in the cultures containing 5000 nM Fe(III) EDTA than those of 5 nM Fe(III) and Fe(II). The growth rate, cell abundance, and total chi a concentration, on the other hand, were higher with daily additions of 5 nM Fe(II) instead of 5 nM Fe(III). Furthermore, cellular Fe quota was higher in the cultures with Fe(III). Cell abundance, chlorophyll a concentration and Fe:Chl a ratio were similar in 5 nMFe(III)+ EDTA cultures (initially or daily added), possibly be due to the negative effects of EDTA on both. The growth rate, cell abundance, total chi a concentration, and Fe quota were higher in cultures with inorganic Fe(II) and Fe(IH) contents, compared to those treated with EDTA containing Fe(II) and Fe(III). E. huxleyi cells seemed not to have used EDTA-bound iron, but their own released ligand to bind iron. Unexpectedly, while cellular iron content of cultures daily supplemented with Fe(II) was low, they exhibited the highest chi a content. The cell-chl a level was higher in daily supplemented cultures, with regard to those supported only initially with iron, evidencing the importance of continuous iron supply in chi a synthesis.
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    The Effect of the Environmental Factors on the Vitamin C (Ascorbic Acid), E (Alpha-tocopherol), ?-carotene Contents and the Fatty Acid Composition of Spirulina platensis
    (Ege Univ, 2006) Isik, Oya; Hizarci, Leyla; Sayin, Selin; Gokpinar, Sevket; Durmaz, Yasar; Goksan, Tolga
    The purpose of this study was to clarify the seasonal variation of vitamin C (ascorbic acid), E (alpha-tocopherol), beta-carotene contents and fatty acid composition of Spirulina platensis grown in the ponds in the subtropic area. While the light intensity, pH and salinity were measured daily, the temperature and dissolved oxygen were measured in day and night. The mean day temperatures were 33.9 +/- 0.4 degrees C in summer and 18.6 +/- 0.5 degrees C in winter. The mean night temperatures were measured 29.9 +/- 0.2 degrees C and 14.4 +/- 0.2 degrees C in summer and winter, respectively. The mean light intensity of 848.3 mu mol/m(2)/s was determined in summer. It was 506.26 +/- 48 mu mol/m(2)/s in winter. The vitamin C content (39.31 +/- 3.63 mg/100 g) of S. platensis grown in winter was found to be higher than in summer. The alpha-tocopherol content (6.57 +/- 1.18 mg/100 g) was higher in summer. However, -carotene contents were found to be similar both in summer and winter. Fatty acid composition was affected from the ambient factors significantly. The higher.-linolenic acid content (22.221 +/- 0.388 %) was found in summer.
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    The effects of EDTA (Ethylenediaminetetraacetate) on the growth of Thalassiosira weissflogii (Bacillariophyta) in 10nM Fe(III) concentration.
    (Ege Univ, 2006) Sayin, Selin; Isik, Oya; Hizarci, Leyla
    Being active in a number of biological events, iron (Fe) is essential trace metal, which is vital for a great many organisms. In an effort to find out a biological approach to the functions of Fe, which are not yet fully understood, and its available marine forms as well as to help determine the factors affecting Fe uptake, the effects of artificial ligand EDTA (Ethylenediaminetetraacetate) (100 mu M) on the growth of Thalassiosira weissflogii were studied in modified F/2 medium consisting of 10nM iron. An ambient temperature of 18 +/- 2 degrees C and lighting intensity of 80 mu mol m(-2) s(-1) were provided during the experiment. Sea water used macro nutrients and EDTA were let through Chelex-100 resin while all other items were freed from any trace metals in acid bath. Acording to the results, it was found that in T. weissflogii culture, EDTA didn't have any effect on cell number, the number of chl-a, growth rate and the pH values which increased proportional to the growth (p>0.05). It was also appeared to be a difference among cell Fe quota (p<0.05).