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PubMed2003

Ca2+ dynamics during membrane excitation of green alga Chara: model simulations and experimental data.

Kinetic investigations of stimulus response coupling in the green alga Chara have revealed that an intermediate second messenger is formed in the process of membrane excitation. This second messenger links electrical stimulation to the mobilization of Ca2+ from internal stores. In the present work, the experimentally based kinetic model, which describes the stimulus-dependent production of the second messenger and Ca2+ mobilization, is combined with a model for inositol 1,4,5-trisphosphate (IP3)-and Ca2+-sensitive gating of a Ca2+-release channel in endomembranes of animal cells. The combination of models allows a good simulation of experimental data, including the all-or-none-type dependence of the Ca2+ response on stimulus duration and complex phase locking phenomena for the dependence of the Ca2+ response on stimulation frequency. The model offers a molecular explanation for the refractory phenomenon in Chara, assigning it to the life time of an inactive state of the Ca2+-release channel. The model furthermore explains the steep dependence of excitation on strength/duration of electrical stimulation as a consequence of an interplay of the dynamical variables in the model.

Calcium↗
PubMed2003

Structural peculiarities dominate the turgor pressure response of the marine alga Valonia utricularis upon osmotic challenges.

The pressure response of (plant) cells to osmotic challenges depends on the reflection coefficient, sigma, of osmotically active solutes; it is less than predicted by the van't Hoff equation if sigma < 1. In Valonia utricularis, sigma is significantly reduced by internal (and, to a lesser extent, by external) unstirred layers, protecting the cytoplasm against vacuolar osmotic fluctuations. As shown by scanning and transmission electron microscopy, diffusion-restricted spaces are formed by innumerable small vacuoles that are interconnected with each other and with the central vacuole. They are embedded in networks of cytoplasmic strands connecting and encircling the organelles. Unstirred layers are also created in the central vacuole by an extensive network of acid mucopolysaccharide filaments (visualized by alcian blue staining). Mucopolysaccharides apparently also affect steady-state turgor by reducing the water activity. When the effective vacuolar osmotic pressure was adjusted to that of the bath by perfusion with an artificial vacuolar sap (AVS), an "offset turgor pressure" of 17 +/- 5 kPa was recorded. Consistent with the ultrastructural data, sigma values less than unity were calculated from the pressure response upon vacuolar addition of KCl or sucrose by perfusion (sigma(iKCl) = 0.63 +/- 0.13; sigma(isuc) = 0.58 +/- 0.17). Dilution of AVS yielded slightly higher sigma(iKCl) values (0.73 +/- 0.35). External addition to the artificial sea water (ASW) indicated that sigma(e) > sigma(i) for these osmotica. However, even in this case, sigma(esuc) (0.86 +/- 0.09) and sigma(ePEG) (0.58 +/- 0.08) were significantly less than sigma(eNaCl) (0.94 +/- 0.05) and sigma(eKCl) (0.91 +/- 0.13), presumably due to unstirred layers within the 4 micro m thick cell wall. Consistent with the low sigma values, a partial replacement of NaCl by osmotically equivalent amounts of sucrose (ASW(suc)), PEG and dextran, respectively, as well as replacement of Cl(-) by the large anion MES(-) induced an 'anomalous' hyposmotic turgor pressure response followed by the usual backregulation of pressure. After a 2-day preincubation in ASW(suc), significantly lower sigma(e) values were obtained both hyperosmotically (sigma(eNaCl) = 0.78 +/- 0.14; sigma(esuc) = 0.72 +/- 0.15) and hyposmotically (sigma(eNaCl) = 0.70 +/- 0.17; sigma(esuc) = 0.63 +/- 0.09), probably due to long-term effects on membrane structure to be elucidated yet. The freshwater alga Chara corallina lacked these apparently closely related structural and biophysical features of Valonia.

Cell Membrane↗
PubMed1997

Separate determination of the electrical properties of the tonoplast and the plasmalemma of the giant-celled alga Valonia utricularis: vacuolar perfusion of turgescent cells with nystatin and other agents.

In the giant-celled marine algae Valonia utricularis the turgor-sensing mechanism of the plasmalemma and the role of the tonoplast in turgor regulation is unknown because of the lack of solid data about the individual electrical properties of the plasmalemma and the vacuolar membrane. For this reason, a vacuolar perfusion technique was developed that allowed controlled manipulation of the vacuolar sap under turgescent conditions (up to about 0.3 MPa). Charge-pulse relaxation studies on vacuolarly perfused cells at different turgor pressure values showed that the area-specific resistance of the total membrane barrier (tonoplast and plasmalemma) exhibited a similar dependence on turgor pressure as reported in the literature for nonperfused cells: the resistance assumed a minimum value at the physiological turgor pressure of about 0.1 MPa. The agreement of the data suggested that the perfusion process did not alter the transport properties of the membrane barrier. Addition of 16 microM of the H+-carrier FCCP (carbonylcyanide p-trifluoromethoxyphenyhydrazone) to the perfusion solution resulted in a drop of the total membrane potential from +4 mV to -22 mV and in an increase of the area-specific membrane resistance from 6.8 x 10(-2) to 40.6 x 10(-2) Omegam2. The time constants of the two exponentials of the charge pulse relaxation spectrum increased significantly. These results are inconsistent with the assumption of a high-conductance state of the tonoplast (R. Lainson and C.P. Field, J. Membrane Biol. 29:81-94, 1976). Depending on the site of addition, the pore-forming antibiotics nystatin and amphotericin B affected either the time constant of the fast or of the slow relaxation (provided that the composition of the perfusion solution and the artificial sea water were replaced by a cytoplasma-analogous medium). When 50 microM of the antibiotics were added externally, the fast relaxation process disappeared. Contrastingly, the slow relaxation process disappeared upon vacuolar addition. The antibiotics cannot penetrate biomembranes rapidly, and therefore, the findings suggested that the fast and slow relaxations originated exclusively form the electrical properties of the plasmalemma and the tonoplast respectively. This interpretation implies that the area-specific resistance of the tonoplast is significantly larger than that of the plasmalemma (consistent with the FCCP data) and that the area-specific capacitance of the tonoplast is unusually high (6.21 x 10(-2) compared to 0.77 x 10(-2) Fm(-2) of the plasmalemma). Thus, we have to assume that the vacuolar membrane of V. utricularis is highly folded (by a factor of about 9 in relation to the geometric area) and/or contains a fairly high concentration of mobile charges of an unknown electrogenic ion carrier system.

Cell Membrane↗
PubMed1999

The effect of an extracellular mucilage on the response to osmotic shock in the charophyte alga Lamprothamnium papulosum.

We have used current/voltage (I/V) analysis to investigate the role played by extracellular mucilage in the cellular response to osmotic shock in Lamprothamnium papulosum. Cells lacking extracellular mucilage originated in a brackish environment (1/3 seawater). These were compared, first with cells coated with thick (approximately 50 micron) extracellular mucilage, collected from a marine lake, and second, with equivalent mucilaginous marine cells, treated with heparinase enzyme to disrupt the mucilage layer. Histochemical stains Toluidine Blue and Alcian Blue at low pH identified the major component of the extracellular mucilage as sulfated polysaccharides. Treating mucilage with heparinase removed the capacity for staining with cationic dyes at low pH, although the mucilage was not removed, and remained as a substantial unstirred layer. Cells lacking mucilage responded to hypotonic shock with depolarization (by approximately 95 mV), cessation of cyclosis, due to transient opening of Ca2+ channels, and opening of Ca2+-activated Cl- channels and K+ channels. Cell conductance transiently increased tenfold, but after 60 min was restored to the conductance prior to hypotonic shock. Mucilaginous cells depolarized by a small amount (approximately 18 mV), but Ca2+ channels failed to open in large enough numbers for cyclosis to cease. Likewise most Ca2+-activated Cl- channels failed to open and conductance increased only approximately 1.2-fold above the prehypotonic level. After 60 min conductance was less than the conductance prior to hypotonic shock. Heparinased mucilaginous cells recovered several aspects of the hypotonic response in cells lacking mucilage. These cells depolarized (by approximately 103 mV); cyclosis ceased, indicating that Ca2+ channels had opened, and conductance increased to approximately 4 times the value prior to hypotonic shock, indicating that Ca2+-activated Cl- channels opened. However, after 60 min, these cells had neither restored membrane potential (and remained at positive values), nor decreased their conductance. It was not possible to determine whether K+ channels had opened. The heparinased cells recovered the normal hypotonic response of mucilaginous cells when heparinase was washed out. Apical seawater cells, which lacked mucilage, were unaffected by heparinase treatment. The results demonstrate that the presence of extracellular sulfated polysaccharide mucilage impacts upon the electrophysiology of the response to osmotic shock in Lamprothamnium cells. The role of such sulfated mucilages in marine algae and animal cells is compared and discussed.

Adhesives↗
PubMed1999

A patch-clamp study of ion channels in protoplasts prepared from the marine alga Valonia utricularis.

The giant marine alga Valonia utricularis is a classical model system for studying the electrophysiology and water relations of plant cells by using microelectrode and pressure probe techniques. The recent finding that protoplasts can be prepared from the giant "mother cells" (Wang, J., Sukhorukov, V.L., Djuzenova, C.S., Zimmermann, U., Müller, T., Fuhr, G., 1997, Protoplasma 196:123-134) allowed the use of the patch-clamp technique to examine ion channel activity in the plasmalemma of this species. Outside-out and cell-attached experiments displayed three different types of voltage-gated Cl(-) channels (VAC1, VAC2, VAC3, Valonia Anion Channel 1,2,3), one voltage-gated K(+) channel (VKC1, Valonia K(+) Channel 1) as well as stretch-activated channels. In symmetrical 150 mm Cl(-) media, VAC1 was most frequently observed and had a single channel conductance of 36 +/- 7 pS (n = 4) in the outside-out and 33 +/- 5 pS (n = 10) in the cell-attached configuration. The reversal potential of the corresponding current-voltage curves was within 0 +/- 4 mV (n = 4, outside-out) and 9 +/- 7 mV (n = 10, cell-attached) close to the Nernst potential of Cl(-) and shifted towards more negative values when cell-attached experiments were performed in asymmetrical 50:150 mm Cl(-) media (bath/pipette; E(Cl(-)) -20 +/- 7 mV (n = 4); Nernst potential -28 mV). Consistent with a selectivity for Cl(-), VAC1 was inhibited by 100 micronM DIDS (4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid). VAC1 was activated by a hyperpolarization of the patch. Boltzmann fits of the channel activity under symmetrical 150 mm Cl(-) conditions yielded a midpoint potential of -12 +/- 5 mV (n = 4, outside-out) and -3 +/- 6 mV (n = 9, cell-attached) and corresponding apparent minimum gating charges of 15 +/- 3 (n = 4) and 18 +/- 5 (n = 9). The midpoint potential shifted to more negative values in the presence of a Cl(-) gradient. VAC2 was activated by voltages more negative than E(Cl(-)) and was always observed together with VAC1, but less frequently. It showed a "flickering" gating. The single channel conductance was 99 +/- 10 pS (n = 6). VAC3 was activated by membrane depolarization and frequently exhibited several subconductance states. The single channel conductance of the main conductance state was 36 +/- 5 pS (n = 5). VKC1 was also activated by positive clamped voltages. Up to three conductance states occurred whereby the main conductance state had a single channel conductance of 124 +/- 27 pS (n = 6). In the light of the above results it seems to be likely that VAC1 contributes mainly to the Cl(-) conductance of the plasmalemma of the turgescent "mother cells" and that this channel (as well as VAC2) can operate in the physiological membrane potential range. The physiological significance of VAC3 and VKC1 is unknown, but may be related (as the stretch-activated channels) to processes involved in turgor regulation.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2003

Molecular phylogeny of conjugating green algae (Zygnemophyceae, Streptophyta) inferred from SSU rDNA sequence comparisons.

Nuclear-encoded SSU rDNA sequences have been obtained from 64 strains of conjugating green algae (Zygnemophyceae, Streptophyta, Viridiplantae). Molecular phylogenetic analyses of 90 SSU rDNA sequences of Viridiplantae (inciuding 78 from the Zygnemophyceae) were performed using complex evolutionary models and maximum likelihood, distance, and maximum parsimony methods. The significance of the results was tested by bootstrap analyses, deletion of long-branch taxa, relative rate tests, and Kishino-Hasegawa tests with user-defined trees. All results support the monophyly of the class Zygnemophyceae and of the order Desmidiales. The second order, Zygnematales, forms a series of early-branching clades in paraphyletic succession, with the two traditional families Mesotaeniaceae and Zygnemataceae not recovered as lineages. Instead, a long-branch Spirogyra/Sirogonium clade and the later-diverging Netrium and Roya clades represent independent clades. Within the order Desmidiales, the families Gonatozygaceae and Closteriaceae are monophyletic, whereas the Peniaceae (represented only by Penium margaritaceum) and the Desmidiaceae represent a single weakly supported lineage. Within the Desmidiaceae short internal branches and varying rates of sequence evolution among taxa reduce the phylogenetic resolution significantly. The SSU rDNA-based phylogeny is largely congruent with a published analysis of the rbcL phylogeny of the Zygnemophyceae (McCourt et al. 2000) and is also in general agreement with classification schemes based on cell wall ultrastructure. The extended taxon sampling at the subgenus level provides solid evidence that many genera in the Zygnemophyceae are not monophyletic and that the genus concept in the group needs to be revised.

Chlorophyta↗
PubMed2004

Comparative analysis of the complete plastid genome sequence of the red alga Gracilaria tenuistipitata var. liui provides insights into the evolution of rhodoplasts and their relationship to other plastids.

We sequenced to completion the circular plastid genome of the red alga Gracilaria tenuistipitata var. liui. This is the first plastid genome sequence from the subclass Florideophycidae (Rhodophyta). The genome is composed of 183,883 bp and contains 238 predicted genes, including a single copy of the ribosomal RNA operon. Comparisons with the plastid genome of Porphyra pupurea reveal strong conservation of gene content and order, but we found major genomic rearrangements and the presence of coding regions that are specific to Gracilaria. Phylogenetic analysis of a data set of 41 concatenated proteins from 23 plastid and two cyanobacterial genomes support red algal plastid monophyly and a specific evolutionary relationship between the Florideophycidae and the Bangiales. Gracilaria maintains a surprisingly ancient gene content in its plastid genome and, together with other Rhodophyta, contains the most complete repertoire of plastid genes known in photosynthetic eukaryotes.

Consensus Sequence↗
PubMed2007

Retrotransposons and tandem repeat sequences in the nuclear genomes of cryptomonad algae.

The cryptomonads are an enigmatic group of unicellular eukaryotic algae that possess two nuclear genomes, having acquired photosynthesis by the uptake and retention of a eukaryotic algal endosymbiont. The endosymbiont nuclear genome, or nucleomorph, of the cryptomonad Guillardia theta has been completely sequenced: at only 551 kilobases (kb) and with a gene density of approximately 1 gene/kb, it is a model of compaction. In contrast, very little is known about the structure and composition of the cryptomonad host nuclear genome. Here we present the results of two small-scale sequencing surveys of fosmid clone libraries from two distantly related cryptomonads, Rhodomonas salina CCMP1319 and Cryptomonas paramecium CCAP977/2A, corresponding to approximately 150 and approximately 235 kb of sequence, respectively. Very few of the random end sequences determined in this study show similarity to known genes in other eukaryotes, underscoring the considerable evolutionary distance between the cryptomonads and other eukaryotes whose nuclear genomes have been completely sequenced. Using a combination of fosmid clone end-sequencing, Southern hybridizations, and PCR, we demonstrate that Ty3-gypsy long-terminal repeat (LTR) retrotransposons and tandem repeat sequences are a prominent feature of the nuclear genomes of both organisms. The complete sequence of a 30.9-kb genomic fragment from R. salina was found to contain a full-length Ty3-gypsy element with near-identical LTRs and a chromodomain, a protein module suggested to mediate the site-specific integration of the retrotransposon. The discovery of chromodomain-containing retroelements in cryptomonads further expands the known distribution of the so-called chromoviruses across the tree of eukaryotes.

Cloning, Molecular↗
PubMed2001

Complex patterns of plastid 16S rRNA gene evolution in nonphotosynthetic green algae.

This study provides a phylogenetic/comparative approach to deciphering the processes underlying the evolution of plastid rRNA genes in genomes under relaxed functional constraints. Nonphotosynthetic green algal taxa that belong to two distinct classes, Chlorophyceae (Polytoma) and Trebouxiophyceae (Prototheca), were investigated. Similar to the situation described previously for plastid 16S rRNA genes in nonphotosynthetic land plants, nucleotide substitution levels, extent of structural variations, and percentage AT values are increased in nonphotosynthetic green algae compared to their closest photosynthetic relatives. However, the mutational processes appear to be different in many respects. First, with the increase in AT content, more transversions are noted in Polytoma and holoparasite angiosperms, while more transitions characterize the evolution of the 16S rDNA sequences in Prototheca. Second, although structural variations do accumulate in both Polytoma and Prototheca (as well as holoparasitic plastid 16S rRNAs), insertions as large as 1.6 kb characterize the plastid 16S rRNA genes in the former, whereas significantly smaller indels (not exceeding 24 bp) seem to be more prevalent in the latter group. The differences in evolutionary rates and patterns within and between lineages might be due to mutations in replication/repair-related genes; slipped-strand mispairing is likely the mechanism responsible for the expansion of insertions in Polytoma plastid 16S rRNA genes.

Chlorophyta↗
PubMed2006

The effect of pH on the uptake and toxicity of copper and zinc in a tropical freshwater alga (Chlorella sp.).

Copper and zinc toxicity to the freshwater alga Chlorella sp. was determined at a range of pH values (5.5-8.0) in a synthetic softwater (hardness 40-48 mg CaCO(3)/L). The effects of the metals on algal growth (cell division) rate were determined after 48-h exposure at pH 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. The toxicity of both metals was pH dependent. As pH decreased from 8.0 to 5.5, the copper concentration required to inhibit the algal growth rate by 50% (IC50) increased from 1.0 to 19 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) concentrations decreased with increasing pH, whereas toxicity was observed to increase. Measurements of extracellular (cell-bound) metal concentrations support the biotic ligand model (BLM) theory of competition between protons (H(+)) and metals for binding sites at the algal cell surface. Higher extracellular metal concentrations were observed at high pH, indicating reduced competition. Independent of pH, both extracellular and intracellular copper were directly related to growth inhibition in Chlorella sp., whereas zinc toxicity was related to cell-bound zinc only. These findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae. Conditional binding constants (log K) were determined experimentally (using measured intracellular metal concentrations) and theoretically (using concentration-response curves) for copper and zinc for Chlorella sp. at selected pH values. Excellent agreement was found indicating the possibility of using concentration-response data to estimate conditional metal-cell binding constants.

Chlorella↗
PubMed2001

Urinary bromide levels probably dependent to intake of foods such as sea algae.

The purpose of the present study is to examine if the bromide (Br) level in urine (Br-U) varies substantially among adult general populations of either sex or of different dietary habits. For this purpose, morning spot urine samples (about 50 per group) were collected from six groups of people, i.e., one group each of men and women in a city in Japan (thus two groups in Japan) and one group each of women in two urban and two rural areas in central and northeast China (four groups in China). The samples were analyzed for Br by ECD-gas chromatography after derivatization to methyl bromide. Br-U essentially followed a normal distribution. Whereas there was only a marginal difference in Br-U between men (7.7 +/- 2.5 mg/L as an arithmetic mean and arithmetic standard deviation) and women (8.1 +/- 2.9 mg/L) in Japan, and no difference between the urban (2.3 +/- 0.8 mg/L) and rural women (2.6 +/- 1.1 mg/L) in China, the difference between Japanese (8.1 +/- 2.9 mg/L) and Chinese women (2.3 +/- 0.8 mg/L for two cities and 2.6 +/- 1.1 mg/L for two villages) was substantial. A literature survey suggested variation in dietary habits, especially that in sea algae intake, is a possible factor affecting the observed difference in Br-U between the two ethnic groups. Contribution of Br in cereals after fumigation with, e.g., methyl bromide, was also thought to be possible. The implication of difference in background Br-U levels is discussed in relation to biological monitoring of exposure to Br-containing industrial chemicals, such as 1- and 2-bromopropane.

Adult↗
PubMed2002

Two species of culturable bacteria associated with degradation of brown algae Fucus evanescens.

The heterotrophic microbial enrichment community established during degradation of brown algae Fucus evanescens was characterized. A two-species bacterial community of marine culturable gamma-proteobacteria consisted of Pseudoalteromonas and Halomonas. The first member of the community, Pseudoalteromonas sp., was highly metabolically active, had bacteriolytic and hemolytic activities, produced proteinases (gelatinase and caseinase), lipases, DNases, and fucoidanhydrolases, laminaranases, alginases, pustulanases, beta-glucosidases, beta-galactosidases, beta-N-acetylglucosaminidases, and beta-xylosidases. The second member of the community, Halomonas marina, produced only caseinase and DNase, and it did not hydrolyze algal polysaccharides. Both members of the studied bacterial community utilized a range of easily assimilable monosaccharides and other low molecular weight organic substances. The results provide an evidence of the complex metabolic interrelations between two members of this culturable community. One of them Pseudoalteromonas sp., most likely plays the major role in the initial stages of algal degradation; the other one, H. marina, resistant to the bacteriolytic activity of the former, is able to utilize the products of degradation of polysaccharides.

Biodegradation, Environmental↗
PubMed2006

Effect of marine bacterial isolates on the growth and morphology of axenic plantlets of the green alga Ulva linza.

The green marine macroalga, Ulva linza, adopts an "atypical" form when grown in the absence of bacteria. Twenty unique strains of periphytic bacteria, isolated from three species of Ulva, were identified by 16S rDNA sequencing. These isolates were assessed for their effect on the growth and morphological development of axenic plantlets of U. linza. Results showed that the effect of bacterial strains was strain- but not taxon-specific. Thirteen isolates returned the aberrant morphology to normal and of these, five also significantly increased growth rate. One isolate increased growth, but had no effect on morphology. Biofilms of some of these isolates stimulated the settlement of Ulva zoospores but there was no correlation between bacterial isolates that stimulated zoospore settlement and those that initiated changes in morphology and/or growth of the cultured alga.

Bacteria↗
PubMed2005

Utilizing the green alga Chlamydomonas reinhardtii for microbial electricity generation: a living solar cell.

By employing living cells of the green alga Chlamydomonas reinhardtii, we demonstrate the possibility of direct electricity generation from microbial photosynthetic activity. The presented concept is based on an in situ oxidative depletion of hydrogen, photosynthetically produced by C. reinhardtii under sulfur-deprived conditions, by polymer-coated electrocatalytic electrodes.

Animals↗
PubMed2000

Inhibition of the development of microorganisms (bacteria and fungi) by extracts of marine algae from Brittany, France.

The inhibitory effects of aqueous, ethanolic and dichloromethane fractions from 16 marine algae from the Atlantic shores of North-East Brittany, France, have been investigated against microorganisms frequently associated with immersed surfaces. The extracts were tested in vitro against isolates of marine fungi, bacteria and yeasts potentially involved at different stages in the formation of biofilms in the sea. The high levels of inhibitory activity of nine extracts against marine fungi and Gram-positive bacteria and their apparent absence of toxicity against larvae of oysters and sea urchins suggests a potential for novel active ingredients.

Animals↗
PubMed2000

In vivo antioxidant role of astaxanthin under oxidative stress in the green alga Haematococcus pluvialis.

Intracellular production of active oxygen in the green alga Haematococcus pluvialis was studied by measuring the capacity for in vivo conversion of 2',7'-dichlorohydrofluorescein diacetate to the fluorescent dye dichlorofluorescein in different algal cell types (i.e., vegetative, immature cyst and mature cyst cells). The increase in formation of dichlorofluorescein by methyl viologen (superoxide anion radical generator) was linear for 2 h in immature cyst cells (low astaxanthin) in a methyl viologen-concentration-dependent manner, while no production was detected in mature (high astaxanthin) cysts. Compared to cyst cells, formation of dichlorofluorescein in vegetative cells (no astaxanthin) was markedly increased by methyl viologen. The formation of dichlorofluorescein in cyst cells was decreased with higher astaxanthin content under excessive oxidative stress. All of the active oxygen species tested (singlet oxygen, superoxide anion radical, hydrogen peroxide and peroxy radical) at 10(-3) M increased the intracellular dichlorofluorescein formation in immature cysts, but did not increase the dichlorofluorescein content of mature cysts. Therefore, astaxanthin in cyst cells appeared to function as an antioxidant agent against oxidative stress.

Antioxidants↗
PubMed1999

Reduction of the nitrogen and carbon content in swine waste with algae and bacteria.

Animal waste causes environmental problems like eutrophication of ground and surface water or the pollution of the atmosphere because of its high NH4+ content. The aim of our study was to fix the nitrogen of swine waste as biomass. Therefore, an isolated alga, Chlorella sp., and bacteria naturally living in liquid manure were grown in batch cultures (containing diluted swine waste supplied with a nutrient solution) and continuous cultures (undiluted liquid manure) to achieve reduction of NH4+ and total organic carbon (TOC) contents. For continuous cultivation, a photobioreactor of our own design was used. The batch cultivation of Chlorella sp. and bacteria in swine waste resulted in good growth of both groups of organisms and in a reduction of 25% NH4+ and 80% TOC. In the continuous cultivation a steady state was not achieved owing to a change in the composition of the bacterial population. NH4+ was totally removed, but NO2- (up to 100 mM) was transiently released. NO3- was not detected. These effects might be explained by the presence of heterotrophic nitrifiers, which are able to oxidize NH4+ to NO2- and to reduce NO2- to gaseous compounds.

Animal Husbandry↗
PubMed2006

Purification and characterization of cadmium-binding protein from unicelluar alga Chlorella sorokinian.

The unicellular green alga Chlorella sorokiniana ANA9 is highly resistant to heavy metals, and its metal-binding proteins are induced in the presence of cadmium. A novel cadmium-binding protein in C. sorokiniana cultured in 100 mg/l cadmium ions for 4 days was isolated and characterized. The crude protein extract was obtained by cell disruption and partly purified by ammonium sulfate precipitation. After purification by anion-exchange chromatography with diethylaminoethyl (DEAE)-Sepharose CL-6B, the protein was further purified by gel filtration with Sephacryl S-100, followed by Sephadex G-75. The molecular weight of the purified protein was determined to be 11.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The cadmium binding capacity of the purified protein was 119 microg/mg. The involvement of thiol coordination in metal-ion binding was confirmed by measuring the ultraviolet spectrum. This article is the first to describe the metallothionein-like cadmium-binding protein from Chlorella species, the expression of which is induced by cadmium exposure.

Chlorella↗