Intact Algae Research Articles

Effects of algal supplementation in feed to broiler breeders on transfer of nutrients and antibodies to chicks and quality of hatchlings

Breeder nutrition is an important factor for chick quality since the chick embryo relies on nutrients available in the egg for growth and development. In addition, the egg is providing the chick with important antibodies that are vital during the first weeks of life. Brown algae contains several bioactive compounds, and dietary supplementation with algal extracts have shown improved gut health and immune responses in both pigs and poultry. The aim of this study was to investigate if feeding the brown algae Saccharina latissima, intact or as an extract, to broiler breeders can affect breeder hens’ antibody responses to vaccination, egg quality and transfer of antibodies and nutrients to the egg and thereby improve the quality of newly hatched chicks. Forty-five hens and nine roosters of the parent lines of the fast-growing broiler Ross 308 were included in the experiment where hens were 31 weeks at the start. The hens were housed individually and fed one of three dietary treatments for seven weeks; (a) control, (b) addition of 0.6% algal meal or (c) addition of 0.08% algal extract. The hens were given a booster vaccination against infectious bronchitis virus (IBV) 21 days after the start of experiment. During experimental days 32–42, hens were naturally mated every 5th day and hatching eggs were collected. A total of 255 chicks were hatched, and chick quality was assessed. Moreover, on chick day three, blood was collected from 48 focal chickens and total immunoglobulin Y levels and specific titres to IBV in serum were determined. The results showed that feeding the brown algae Saccharina latissima, intact or as an extract to broiler breeders did not affect egg production, egg quality, antibody responses to vaccination or transfer of antibodies from hen to chick. However, feeding intact algae significantly increased the levels of iodine and decreased the level of selenium in the eggs and resulted in a lower proportion of chicks with maximum quality score. Interestingly, algal feeding, both intact and as an extract, increased the abdominal fat pad in broiler breeders by about 17% without affecting BW. In conclusion, supplementation of broiler breeder diets with algal extract from Saccharina latissima, but not intact algal meal is a promising dietary strategy to increase the abdominal fat pad without causing any adverse effects on nutrient level in eggs or chick quality.

Assessing the Effect of Modified Clay on the Toxicity of Karenia mikimotoi Using Marine Medaka (Oryzias melastigma) as a Model Organism.

Blooms of the toxic dinoflagellate Karenia mikimotoi could threaten the survival of marine life, and modified clay (MC) is considered a promising method for the control of harmful algal blooms. Here, using marine medaka as the model organism, the toxicity of K. mikimotoi before and after MC disposal was investigated. The results showed that only a certain density of intact K. mikimotoi cells could cause obvious damage to fish gills and lead to rapid death. A systematic analysis of morphology, physiology, and molecular biology parameters revealed that the fish gills exhibited structural damage, oxidative damage, osmotic regulation impairment, immune response activation, and signal transduction enhancement. MC can flocculate K. mikimotoi rapidly in water and reduce its toxicity by reducing the density of intact algae cells and hemolytic toxicity. The results indicate that MC is an effective and safe method for controlling K. mikimotoi blooms.

Examining the Relationship Between the Testate Amoeba Hyalosphenia papilio (Arcellinida, Amoebozoa) and its Associated Intracellular Microalgae Using Molecular and Microscopic Methods

Symbiotic relationships between heterotrophic and phototrophic partners are common in microbial eukaryotes. Among Arcellinida (Amoebozoa) several species are associated with microalgae of the genus Chlorella (Archaeplastida). So far, these symbioses were assumed to be stable and mutualistic, yet details of the interactions are limited. Here, we analyzed 22 single-cell transcriptomes and 36 partially-sequenced genomes of the Arcellinida morphospecies Hyalosphenia papilio, which contains Chlorella algae, to shed light on the amoeba-algae association. By characterizing the genetic diversity of associated Chlorella, we detected two distinct clades that can be linked to host genetic diversity, yet at the same time show a biogeographic signal across sampling sites. Fluorescence and transmission electron microscopy showed the presence of intact algae cells within the amoeba cell. Yet analysis of transcriptome data suggested that the algal nuclei are inactive, implying that instead of a stable, mutualistic relationship, the algae may be temporarily exploited for photosynthetic activity before being digested. Differences in gene expression of H. papilio and Hyalosphenia elegans demonstrated increased expression of genes related to oxidative stress. Together, our analyses increase knowledge of this host-symbiont association and reveal 1) higher diversity of associated algae than previously characterized, 2) a transient association between H. papilio and Chlorella with unclear benefits for the algae, 3) algal-induced gene expression changes in the host.

Effect of extracellular polymeric substances on arsenic accumulation in Chlorella pyrenoidosa

Inorganic arsenic (iAs) in its dominant dissolved phase in the environment is known to pose major threats to ecological and human health. While the biological effects in many arsenic-bearing freshwaters have been extensively studied, the behavior and bioaccumulation of dissolved iAS in the presence of extracellular polymeric substances (EPS) still remains to be a critical knowledge gap. In this study, the uptakes and kinetic characteristics of iAs were studied using Chlorella pyrenoidosa (a typical freshwater green algae) by addressing the different effects of EPS on arsenite (AsШ) and arsenate (AsV). The arsenic uptake capacity increased as the exposure concentration increased from 0 to 300 µmol L−1, and the uptake rate constants (Ku) in the Bio-dynamic model were greater for AsV than AsШ (0.63–11.57 L g−1 h−1 vs. 0.44–5.43 L g−1 h−1). The toxic effects as mitigated by EPS were observed through the morphological changes of algal cells by TEM and SEM. When compared with the EPS-free algal cells (EPS-F), EPS-covered cells (EPS-C) had a higher arsenic adsorption capacity through EPS-enhanced surface adsorption and reduced intracellular uptake. The overall decrease (35% and 23.3% for AsШ and AsV, respectively) in the maximum uptake capacity in intact algae cells favors cell’s tolerance to the toxic effects of iAs. These observed discrepancies between AsШ and AsV and between EPS-C and EPS-F were further elucidated through morphological images (TEM and SEM) and molecular/atomic spectroscopic data that combine three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Altogether, the spectroscopic evidence revealed the interactions of iAs with C–O–C, C–O–H and –NH2 functional groups in EPS’ tyrosine- and tryptophan-like proteins as the binding sites. Overall, this study for the first time provides comprehensive evidence on the iAs-EPS interactions. Such insights will benefit our understanding of the biogeochemical processes of iAs and the strategic development of bioremediation techniques involving microalgae in the natural and engineered systems.

La(III) and Ce(III) biosorption on sulfur functionalized marine brown algae Cystoseira indica by xanthation method: Response surface methodology, isotherm and kinetic study

In this study, chemically modified Cystoseira indica brown algae by xanthation method was utilized to study the biosorption of La(III) and Ce(III) ions from the aqueous solutions under batch mode. The effects of four variables including pH (2–6), temperature (25–55 °C), biosorbent dosage (0.5–2.5 g L–1) and initial metal concentration (50–250 mg L–1) were evaluated and optimized using Response Surface Methodology (RSM) based on the Central Composite Design (CCD). A low P–value and high coefficient of determination (R2) implied the accuracy and validity of the proposed quadratic models. The results showed that the xanthation improved the performance of C. indica than the intact and Ca–pretreated ones. Performing experiments under optimal condition sets produced maximum biosorption capacities of 185.44 and 172.33 mg g–1 for La(III) and Ce(III), respectively. In order to characterize the provided biosorbents, FTIR analyses were carried out. Results revealed that the dominant functional groups in the binding process were hydroxyl, carboxyl and amide in the intact algae while xanthation caused addition of sulfur groups that participated in binding process and increased the sorption capacities of both metal ions. The equilibrium and kinetic studies revealed that the Freundlich isotherm model and the double–exponential kinetic model were in the better fitness with the La(III) and Ce(III) experimental data. Moreover, the results showed that the presence of Th(IV) ions decreased the biosorption capacities of both metal ions. In conclusion, the present work showed that the xanthated C. indica could be a proper biosorbent for La(III) and Ce(III) biosorption from aqueous solutions.

Epifluorescencia en la nutrición de larvas de Strombus gigas y Strombus pugilis (Mesogastropoda: Strombidae)

In order to increase the scientific knowledge about the ingestion and digestion processes of the microalga Tetraselmis suecica by veliger larvae, we did a comparative analisis of feeding kinetics of two Caribbean conch lar­vae: Queen conch, Strombus gigas, and Pighting conch, Strombus pugilis. These kinetics have been determined in a direct way by means of epifluorescence microscopyc with this technique the potential nutritive value of different microalgae, can be detected in terms of their ingestion and digestion rates. Given the all to fluorescence of algal cells and transparency of both larvae tissues and shell, the algae within the stomach, their lisis and subsequent degradation are observed. The evolution of the ingestion and digestion processes can be follow in live larvae, where other events like the expulsion of intact algae cells initially ingested by the larvae can be observed. The nutritional effects of T. suecica on veliger larvae are explained infunction of a cromatic scale of four nutritional stages, and by means of temporal and absolute ingestion and digestion indices.

Titanium Dioxide (TiO2) nanoparticles more strongly affect bacteria compared to algae in stream ecosystems

Titanium dioxide (TiO2) is a novel nano-particulate contaminant found in surface waters. Nano-TiO2 is commonly used in numerous pharmaceutical and personal care products ranging from make-up to pill casings, and is an additive in food and household products. Despite the commercialized use of TiO2, its increased presence in surface waters, and toxic effects on stream organsims, little information exists on how nano-TiO2 affects stream ecosystems as a whole. We examined the effect of various concentrations (0.5 - 3 mg/L) of nano-TiO2 on stream ecosystems by measuring the response of algal and microbial communities to acute (12 hr) and chronic (22 day) exposures. We measured gross primary production (GPP), community respiration (CR), and chlorophyll a (chl a) concentrations on intact algae from a local stream.We expected metabolic function of both algal and microbial components of the benthic biofilm to decline with exposure due to sensitivities to metal oxides. However, we found exposure to any of the concentrations of nano-TiO2 tested caused CR to decrease compared to controls, but, GPP either increased or stayed the same as our controls. We found algal chl a concentraions to increase in the high exposure treatment. Since nano-TiO2 had a negative effect on the microbes, we hypothesized that either autotrophs were released from microbial competition and increased chl a production, or that shading from TiO2 particles may have caused increased chl a production. Additional studies investigating the effects of higher concentrations and longer exposure times to these compounds are warranted.

Oil sands process-affected water impairs feeding by Daphnia magna

Growth in extraction of bitumen from oil sands has raised concerns about influences of this industry on surrounding environments. Water clearance rate (a surrogate of feeding rate by Daphnia magna) in water containing D. magna exposed to oil sands process-affected water (OSPW) and its principal components, dissolved component (DC) and suspended particulate matter (SPM), was reduced to 72, 29, and 59% of controls, respectively. This study also examined several possible mechanisms for the observed changes algal cell density (i.e., feeding rate). There was no change in the digestive enzymes trypsin or amylase when D. magna were exposed to DC or SPM; however, exposure to total OSPW reduced trypsin activity. Mandible rolling or post-abdominal rejections, which are indicators of feeding and palatability of food, were not affected by any exposures to OSPW. Beating of thoracic limbs, which provides water flow toward the feeding groove, was reduced by exposure to SPM or total OSPW. Peristaltic activity was reduced by exposure to DC, which then might result in reduced digestion time in D. magna exposed to DC, SPM or whole OSPW. All treatments caused an increase in numbers of intact algae cells in the hindgut and excreted material. These results suggest that both DC and SPM affect feeding of D. magna by impairing actions of the digestive system, but most probably not by reducing rates of ingestion.

Bioremediation of cadmium-contaminated water systems using intact and alkaline-treated alga (Hydrodictyon reticulatum) naturally grown in an ecosystem

ABSTRACTCadmium can enter water, soil, and food chain in amounts harmful to human health by industrial wastes. The use of intact and NaOH-treated dried algal tissues (Hydrodictyon reticulatum), a major ecosystem bio-component, for Cd removal from aqueous solutions was characterized. Cadmium biosorption was found to be dependent on solution pH, bioadsorbent dose, the interaction between pH and dose, contact time, and initial Cd concentration. The experimental results indicated that the biosorption performance of alkaline-treated algal tissues was better than that of intact tissues. The maximum biosorption capacities were 7.40 and 12.74 mg g−1 for intact and alkaline-treated bioadsorbents, respectively, at optimum operating conditions. Biosorption reaches equilibrium after 24 and 240 minutes of contact, respectively, for alkaline-treated and intact bioadsorbents. Cadmium biosorption was best fitted to Langmuir isotherm model (R2 ≈ 0.99) and the kinetic study obeyed the pseudo-second-order kinetic model, which suggests chemisorption as the rate-limiting step in the biosorption process. Alkaline-treated algal tissues can be used as a new material of low-cost bioadsorbent for continuous flow rate treatment systems.

The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae.

Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag+, C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag+, and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs.

Relative Contributions of Various Cellular Mechanisms to Loss of Algae during Cnidarian Bleaching.

When exposed to stress such as high seawater temperature, corals and other cnidarians can bleach due to loss of symbiotic algae from the host tissue and/or loss of pigments from the algae. Although the environmental conditions that trigger bleaching are reasonably well known, its cellular and molecular mechanisms are not well understood. Previous studies have reported the occurrence of at least four different cellular mechanisms for the loss of symbiotic algae from the host tissue: in situ degradation of algae, exocytic release of algae from the host, detachment of host cells containing algae, and death of host cells containing algae. The relative contributions of these several mechanisms to bleaching remain unclear, and it is also not known whether these relative contributions change in animals subjected to different types and/or durations of stresses. In this study, we used a clonal population of the small sea anemone Aiptasia, exposed individuals to various precisely controlled stress conditions, and quantitatively assessed the several possible bleaching mechanisms in parallel. Under all stress conditions tested, except for acute cold shock at 4°C, expulsion of intact algae from the host cells appeared to be by far the predominant mechanism of bleaching. During acute cold shock, in situ degradation of algae and host-cell detachment also became quantitatively significant, and the algae released under these conditions appeared to be severely damaged.

Winter snowfall can have a positive effect on photosynthetic carbon fixation and biomass accumulation of biological soil crusts from the Gurbantunggut Desert, China

AbstractWinter snowfall is an important factor in the growth and development of biological soil crusts (BSCs) in temperate desert regions of China. In this study, intact algae, lichen, and moss crusts from the Gurbantunggut Desert were collected and exposed to five experimental treatments—snow removal (0S), snow decrease to half that of ambient conditions (1/2S), ambient snow (S), snow increase to 1.5 times that of ambient conditions (3/2S), and snow increase to twice that of ambient conditions (2S)—to evaluate the effect of snowfall on the ecophysiological parameters of the BSCs during the melt and at the end of the growing period. The results clearly identified differences in physiological and ecological indexes between snowfall manipulation treatments in March, and further found that the values of most of the ecophysiological indexes were influenced by snow removal/reduction treatments, the type of BSC and their interaction effect. The chlorophyll fluorescence parameters, chlorophyll content, and the rates of photosynthesis and respiration of all three types of crust declined because of decreased soil water content with decreased snow cover, and this effect would likely be even greater under conditions of decreased precipitation. The rates of photosynthesis and respiration of the main types of BSC were changed by variations in the winter snowfall, and confirmed the existence of long‐term snowfall impacts on photosynthetic carbon fixation and biomass accumulation. These results provide a foundation for future studies to assess the potential effects of snowfall on the carbon sequestration of BSCs from arid and semi‐arid regions.

Evaluation of photosynthetic electrons derivation by exogenous redox mediators

Oxygenic photosynthesis is the complex process that occurs in plants or algae by which the energy from the sun is converted into an electrochemical potential that drives the assimilation of carbon dioxide and the synthesis of carbohydrates. Quinones belong to a family of species commonly found in key processes of the Living, like photosynthesis or respiration, in which they act as electron transporters. This makes this class of molecules a popular candidate for biofuel cell and bioenergy applications insofar as they can be used as cargo to ship electrons to an electrode immersed in the cellular suspension. Nevertheless, such electron carriers are mostly selected empirically. This is why we report on a method involving fluorescence measurements to estimate the ability of seven different quinones to accept photosynthetic electrons downstream of photosystem II, the first protein complex in the light-dependent reactions of oxygenic photosynthesis. To this aim we use a mutant of Chlamydomonas reinhardtii, a unicellular green alga, impaired in electron downstream of photosystem II and assess the ability of quinones to restore electron flow by fluorescence. In this work, we defined and extracted a “derivation parameter” D that indicates the derivation efficiency of the exogenous quinones investigated. D then allows electing 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone and p-phenylbenzoquinone as good candidates. More particularly, our investigations suggested that other key parameters like the partition of quinones between different cellular compartments and their propensity to saturate these various compartments should also be taken into account in the process of selecting exogenous quinones for the purpose of deriving photoelectrons from intact algae.

Extraction and Analysis of Oxylipins from Macroalgae Illustrated on the Example Gracilaria vermiculophylla.

Oxylipins are natural products that are derived by oxidative transformations of unsaturated fatty acids. These metabolites are found in a wide range of organisms from the animal kingdom to plants and algae. They represent an important class of signaling molecules, mediating intra- and intercellular processes such as development, inflammation, and other stress responses. In addition, these metabolites directly function as chemical defense against grazers and pathogens. In the red alga Gracilaria vermiculophylla, oxylipin production is initiated by mechanical tissue disruption and can also be induced in intact algae in response to external stress signals. The defense metabolites mostly result from the lipase- and lipoxygenase-mediated conversion of phospho- and galactolipids. Oxylipins can vary greatly in their size, degree of unsaturation, oxidation state, and functional groups. But also isomers with only subtle chemical differences are found. A variety of methods have been developed for separation, detection, and identification of oxylipins. This chapter focuses on the analysis of oxylipins in macroalgae and covers all aspects from sample preparation (including protocols for the investigation of oxylipins in wounded and intact algal tissue), extraction, purification, and subsequent analysis using liquid chromatography coupled to a UV detector or a mass spectrometer. The protocols developed for G. vermiculophylla can be readily adapted to the investigation of other macroalgae.

Raman Spectroscopic Insights into the Chemical Gradients within the Wound Plug of the Green Alga Caulerpa taxifolia

The invasive unicellular green macroalga Caulerpa taxifolia has spread dramatically in the Mediterranean Sea over the last decades. Its success is based on rapid plug formation after wounding, to prevent the loss of cell content. This quick and efficient process involves the rapid transformation of the secondary metabolite caulerpenyne to the reactive 1,4-dialdehyde oxytoxin 2, which acts as a protein crosslinker. The main metabolites of the wound plug were identified as proteins, caulerpenyne derivatives, and sulfated polysaccharides. Because of a methodological deficit, however, the detailed distribution of the compounds within the wound plug of C. taxifolia was unknown. This study demonstrates the suitability of FT-Raman spectroscopy for the noninvasive in vivo determination of caulerpenyne and its derivatives, as well as β-carotene, from signals with special spectral features within the wound plug and the adjacent intact alga tissue, with a resolution of 100 μm. FT-Raman spectra allowed four different zones with distinct chemical compositions around the region of wounds to be characterized. Gradients of the investigated metabolites within the wound plug and the alga could be determined. Moreover, various caulerpenyne derivatives could be identified spectroscopically, and this has led to a mechanistic proposal for the internal and the external wound plug formation.

A TRP Protein From Chlamydomonas Reinhardtii is a Functional Plasma Membrane Ion Channel Associated to Algae Sensory System

Sensory modalities are fundamental for navigation through an ever changing environment, therefore, a vital need for moving organisms. Possible to be found expressed on insects and mammals, TRP channels are known mediators for cellular sensing. Chlamydomonas reinhardtii is a motile single celled green algae that swim in fresh water helped by two flagella. C. reinhardtii cells are able to move guided by photo-, mechano-, and chemo- sensory input, first detected by membrane receptors and further transduced to the cilia by a depolarization potential. Although TRP channels seem to be absent in plants, in silico analyses suggested that Chlamydomonas possess genomic sequences encoding for TRP ion channels. Here we described a C. reinhardtii version of a TRP channel with resemblance to mammalian TRPM channels. Electrophysiological experiments conducted on intact algae and patch clamp recordings performed on HEK-293T cells expressing the crTRPM clone were combined with behavioural studies. Taken together, our results suggest that a crTRPM channel conductance is strongly associated with sensing and navigation, highlighting the role of these proteins on sensory systems throughout evolution.Funding: FONDECYT 1110906

Characteristics of the Digestive Vacuole Membrane of the Alga-Bearing Ciliate Paramecium bursaria

Cells of the ciliate Paramecium bursaria harbor symbiotic Chlorella spp. in their cytoplasm. To establish endosymbiosis with alga-free P. bursaria, symbiotic algae must leave the digestive vacuole (DV) to appear in the cytoplasm by budding of the DV membrane. This budding was induced not only by intact algae but also by boiled or fixed algae. However, this budding was not induced when food bacteria or India ink were ingested into the DVs. These results raise the possibility that P. bursaria can recognize sizes of the contents in the DVs. To elucidate this possibility, microbeads with various diameters were mixed with alga-free P. bursaria and traced their fate. Microbeads with 0.20μm diameter did not induce budding of the DVs. Microbeads with 0.80μm diameter produced DVs of 5-10μm diameter at 3min after mixing; then the DVs fragmented and became vacuoles of 2-5μm diameter until 3h after mixing. Each microbead with a diameter larger than 3.00μm induced budding similarly to symbiotic Chlorella. These observations reveal that induction of DV budding depends on the size of the contents in the DVs. Dynasore, a dynamin inhibitor, greatly inhibited DV budding, suggesting that dynamin might be involved in DV budding.

Macroalgae reduce growth of juvenile corals but protect them from parrotfish damage

Inhibition of early life stages of corals by benthic algae is a critical bottleneck to the recovery and resilience of corals. Increasingly frequent and severe disturbances are causing large- scale coral mortality, usually followed by colonisation and dominance by benthic algae. The capacity of corals to re-establish in such algal-dominated habitats will depend on the effects of the algae on growth and survivorship of juvenile corals. We experimentally evaluated the competition between juvenile corals Porites astreoides and algae and the effects of algae on the exposure of juvenile corals to damage by parrotfishes (family Scaridae) in a Colombian Caribbean reef. We also explored whether those effects were consistent among climatic seasons (upwelling and non-upwelling). Ben- thic algae had negative and positive effects on the juvenile corals. The removal of algal turfs and fleshy macroalgae enhanced coral growth. Unexpectedly, removal of algae from around the juvenile corals increased predation upon the corals by parrotfishes. When algae were removed, at least 50% of the corals were grazed by parrotfishes, but no bites were observed on corals with intact algae. Coral growth and parrotfish damage were not affected by season. However, damage by parrotfishes neither lessened survivorship nor resulted in negative growth for any of the grazed coral colonies. The beneficial effects of algae in protecting the juvenile corals from parrotfish damage seem to be outweighed by the negative effects of the algae on coral-algal competition. Understanding such complexities in the interactions between algae and early life stages of corals can provide insight into the roles of algae in coral reef resilience.

The photophysics of cryptophyte light-harvesting

Recent studies of the optical properties and the critical role of phycobiliproteins in the absorption of green light for photosynthesis in cryptophyte algae ( Rhodomonas CS24 and Chroomonas CCMP270) are reviewed. Investigations of two different isolated proteins, phycoerythrin 545 (PE545) and phycocyanin 645 (PC645), whose crystal structures are known to 0.97 and 1.4 Å resolution respectively, are described. Steady-state spectroscopic measurements, including polarization anisotropy and circular dichroism, are used in combination with ultrafast transient grating and transient absorption techniques to elucidate a detailed picture of resonance energy transfer within the light-harvesting proteins. Quantum chemical calculations are employed to estimate phycobilin excited states, and generate transition density cubes which are used to calculate accurately the electronic coupling between the chromophores in PE545 and PC645. Energy transfer dynamics are examined using the generalized Förster theory. Kinetic models for energy transfer dynamics in both proteins are presented for comparison. Investigations of energy transfer from phycoerythrin 545 to chlorophyll-containing light harvesting complexes and photosystems in the intact algae Rhodomonas CS24 and Chroomonas CCMP270 are also reported.

Lead and copper effects on lipid metabolism in cultured lichen photobionts with different phosphorus status

We evaluated the ability of heavy metals (copper, lead) to alter lipid metabolism in four algal lichen photobionts following short term exposure. Metal concentrations (10 μM) were equivalent to environmentally relevant levels that have been reported to have effects on intact algae. The algae were grown under normal or deficient phosphate conditions to assess any interactions with the heavy metal stress. Given the frequent sensitivity of lichens to copper and lead, there were surprisingly small changes on lipid metabolism, as assessed by radiolabelling from [1- 14C]acetate. The main effects, which were seen in a number of cases, were an overall inhibition of total lipid labelling and a relative increase in the labelling of triacylglycerols in the non-polar fraction. Both of these changes can be viewed as reflecting general toxicity of heavy metals. The Coccomyxa photobiont species were more sensitive than Trebouxia species, which fits with the general distribution of the latter in lichens inhabiting harsh environments.