Genera Of Cyanobacteria Research Articles

The Effects of Pulsed Streamerlike Discharge on Cyanobacteria Cells

Recently, cyanobacteria blooms (or water blooms) occurred on the surface of water bodies frequently and extensively due to eutrophia of the water. That has posed more and more serious environmental problems worldwide. In this paper, the effects of pulsed streamerlike discharge on M. aeruginosa cells are reported, which are one genus of cyanobacteria and ease to form water blooms. A stainless needle with a diameter of 30 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$muhboxm$</tex> was employed as a point discharge electrode, which is 15-cm apart from the cylinder cathode, and a 2- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$muhboxs$</tex> 160-kV pulse was applied. A pulsed streamerlike discharge was obtained in the water filled with cyanobacteria cells (named as sample water in this paper). From the experimental result, it can be found that the discharge collapsed the intracellular-structure gas vesicles in the M. aeruginosa cells, and the colonies of the cells sank to the bottom of the discharge chamber and rotten gradually.

Evaluating genotoxicity associated with microcystin-LR and its risk to source water safety in Meiliang Bay, Taihu Lake

In recent years cyanobacteria blooms have become a severe problem in Taihu Lake, a large shallow eutrophic lake in China. Microcystins produced by certain genera of cyanobacteria can affect public health in this area because of their acute and chronic toxic effects. In this study, samples of cyanobacteria were collected and extracted by two solvent systems. The extracts were tested with three short-term genotoxicity assays, the ara test, the Ames test, and the SOS/umu test. In addition, temporal variation in the concentrations of microcystin-LR in the water samples was determined and monitored by an ELISA assay. Then the concentration of microcystin-LR in the drinking water was estimated. The risk of microcystin-LR exposure by drinking water was assessed according to tolerable daily intake (TDI). The three genotoxicity assays showed negative results regardless of the solvent system used, and there were clear inconsistencies in the spatiotemporal profiles of genotoxic potential and microcystin concentrations in Taihu Lake. Risk assessment showed that the drinking water from Taihu Lake was not safe from the end of July to the beginning of November because of a high concentration of microcystin-LR. Our study indicated the drinking water from Taihu Lake posed a risk because of the microcystin-LR, although it was neither genotoxic nor associated with genotoxicity of the lake water.

Liquid chromatography–tandem mass spectrometry and accurate m/ z measurements of cyclic peptide cyanobacteria toxins

Microcystins are cyclic peptide hepatotoxins that are produced by several genera of cyanobacteria. We briefly review the molecular structural features of 67 reported cyclic heptapeptide microcystins and a related cyclic pentapeptide toxin. These substances present a significant analytical challenge because multiple toxins are often found in any given cyanobacteria or water sample, and it is likely that some structural variants have yet to be identified. We briefly describe a hybrid linear ion trap – Fourier transform ion cyclotron resonance (LT-FT-ICR) mass spectrometer equipped with a liquid chromatography (LC)/electrospray sample-introduction system. This instrument system was used to obtain LC/mass spectrometry (MS) data from the commercially available cyanobacteria toxins (microcystin-LR, -YR, -RR and nodularin). We review the electrospray mass spectra of these toxins and the significance of accurate m/ z measurements of toxin precursor and product ions. We discuss the collision-induced dissociation of [M + H] +, [M + H] 2+, and fragment ions in terms of ion-fragmentation pathways and mechanisms. The principal focus of this review is the potential for the efficient determination of microcystin structures with these MS techniques when no analytical standards are available or when new microcystin toxins are present in a sample.

Nicotine effects on the activity of mice exposed prenatally to the nicotinic agonist anatoxin-a

Anatoxin-a is a nicotinic agonist produced by several genera of cyanobacteria, and has caused numerous deaths of wildlife, livestock and domestic animals world-wide. Several studies in the literature have shown that exposure of mice and rats to nicotine early in development alters its effects when the rodents are subsequently challenged with nicotine. We therefore determined the effect of nicotine on the motor activity of adult mice that had been exposed prenatally to anatoxin-a. Pregnant CD-1 mice received either saline vehicle or one of two doses of (+/−) anatoxin-a (125, 200 ug/kg), i.p., on GD13–17. As adults (8 months), control mice of both genders were used to determine the effect of nicotine (0, 0.1, 0.3, 1.0 or 3.0 mg/kg, s.c.) on motor activity measured for 30-min in a photocell device. Under these conditions, nicotine produced dose-related decreases in both horizontal and vertical activity, with an ED50 estimated to be 0.65 mg/kg. Next, additional control mice and mice exposed prenatally to anatoxin-a received the nicotine ED50 and saline vehicle, in a counterbalanced fashion, with one week separating treatments. Nicotine decreased both horizontal and vertical activity in all mice, regardless of prenatal anatoxin-a treatment. Thus, no enduring effects of prenatal anatoxin-a were obtained in adult mice following nicotine challenge.

Optimization of intracellular microcystin extraction for their subsequent analysis by high-performance liquid chromatography

Microcystins are a family of heptapeptide hepatotoxins produced by some genera of cyanobacteria. These toxins have been responsible for the illness and death of both animals and humans. Due to their hazard to human health, extraction of all intracellular microcystin variants is required to characterize and quantify all microcystins present in a sample. To date, there is little work reported comparing results obtained with different extraction methods. Findings reported to date indicate that selection of solvent will vary depending on sample and its microcystin contents. In the present work, a wide range of extraction volumes and solvents were evaluated over a range of pH and extraction times in order to optimize a suitable method for the extraction of a wide range of microcystins. The number of extractions required was also studied. This study was carried out using mainly two laboratory cultures which contain microcystin variants with quite different hydrophobicities. This is the first time that the most commonly used solvents for intracellular microcystin extraction have been studied in detail.

Cyanobacterial Photosystem I lacks specificity in its interaction with cytochrome c6 electron donors

In cyanobacteria, plastocyanin and cytochrome c(6), the alternate donor proteins to Photosystem I, can be acidic, neutral or basic; the role of electrostatics in their interaction with photosystem I varies accordingly. In order to elucidate whether these changes in the electron donors' properties correlate with complementary changes in the docking site of the corresponding photosystem, we have investigated the kinetics of reactions between three cytochrome c(6) with isoelectric points of 5.6, 7.0 and 9.0, with Photosystem I particles from the same three genera of cyanobacteria which provided the cytochromes. The model systems compared here thus sample the full range of charge properties observed in cytochromes c(6): acidic, basic and neutral. The rate constants and dependence on ionic strength for photosystem I reduction were distinctive for each cytochrome c(6), but independent of Photosystem I. We conclude that the specific structural features of each cytochrome c(6) dictate their different kinetic behaviours, whereas the three photosystems are relatively indiscriminate in docking with the electron donors.

A comparative study of cyanobacterial diversity in polluted and unpolluted microbial mats by means CLSM

Abstract This paper is a summary of the results obtained from a study of the diversity of cyanobacteria in oil polluted and unpolluted natural environments. Our work group identified the different genera of cyanobacteria by means of CLSM, as this technique is specifically appropriate for studying the diversity of these microorganisms in stratified bentonic environments (microbial mats). The cyanobacteria identified in pristine ecosystems show that the most abundant cyanobacteria correspond to the genera: Microcoleus chthonoplastes, Oscillatona sp., Lyngbya sp., Leptolyngbya sp., and Limnothrix sp. Phormidium sp.and Pseudanabaena sp. were also identified, although they were less abundant. On the other hand, in the ecosystems heavily polluted with oil (Etang de Berre) neither Microcoleus chthonoplastes nor Oscillatoria sp. were detected, although the other genera mentioned were. With respect to coccoid cyanobacteria, the most abundant groups in the Ebro delta were Gloeocapsa sp. and Synechocystis sp. and al...

Typology of secondary cyanobacterial metabolites from minimum spanning tree analysis

Recently, two main events have spurred a rapid increase in cyanobacteria chemical, toxicological, and ecological research. The first deals with the interest in isolating compounds from these organisms as source of active products with potential therapeutic applications. The second pertains the crucial problem of harmful cyanobacterial blooms in the aquatic environments. In this context, 594 secondary metabolites belonging to more than 30 genera of cyanobacteria were retrieved from literature. In order to perform their typology, they were first associated with 87 different molecular archetypes and two orphan classes. These 89 groups of molecular structures were then confronted to minimum spanning tree analysis. Attempts were made to graphically derive chemotaxonomical relationships. The interest of QSAR models for estimating the potential pharmacological interest of the cyanobacterial secondary metabolites was also discussed.

Microcystin-LR affects cytoskeleton and morphology of rabbit primary whole embryo cultured cells in vitro

Microcystin-LR is the most frequently studied cyclic heptapeptide produced by different genera of cyanobacteria and is hepatotoxic to livestock and human populations. The adverse effects of microcystin-LR on morphology and cytoskeletal elements in different stages of early embryonal development have been studied in vitro. Embryos and whole embryo cultures have been exposed to microcystin-LR (10–100 μM). Actin filaments were visualized by fluorescence staining and the microtubular network labelled by immunostaining. Growth, development and cytoskeleton organization of the embryos embedded in zona pellucida are not affected by microcystin-LR in concentrations up to 100 μM, while whole embryo cell cultures are affected by the presence of microcystin-LR in the culture medium. High microcystin-LR concentrations (100 μM) cause cells to be detached and destroyed, while lower concentrations (10–20 μM) profoundly affect actin and microtubule organization. These effects are confirmed also by the presence of transformed microcystin-LR in all the media at the lowest concentrations. It seems that the changes to the cells are far more serious than that expressed in cell morphology. From our experiments we conclude that the presence of zona pellucida is an effective way of embryo protection against xenobiotics like microcystin-LR.

Production of novel polyclonal antibodies against the cyanobacterial toxin microcystin-LR and their application for the detection and quantification of microcystins and nodularin

A novel conjugation method was developed by linking the hapten, the cyanobacterial hepatotoxin microcystin-LR, via 2-mercaptoethylamine to keyhole limpet haemocyanin. Polyclonal antisera were raised against this conjugate and an indirect competitive immunoassay (ELISA) developed which can detect purified microcystin-LR and the toxin in extracts of cyanobacteria from fresh-, brackish and marine waters. The cross-reactivity of the microcystin-LR antibodies was investigated with a range of purified microcystin variants (-LR, -LA, -LY, -LW, -LF, -D-Asp 3-RR, and -Asp 3( Z)-Dhb 7-HtyR) and nodularin. The antibodies cross-reacted well with all microcystin and nodularin variants. The microcystin-LA was the most readily detectable, followed by microcystins-LR, -LF, -LW, -D-Asp 3-RR, -LY, nodularin and microcystin-Asp 3( Z)-Dhb 7-HtyR. Extracts from several genera of cyanobacteria were investigated by the ELISA and the results compared to high performance liquid chromatography with diode array detection (HPLC–DAD). By the ELISA procedure, 60% were positive, compared to detection of microcystins in 45% of the samples by HPLC–DAD. Analysis of microcystin-LR equivalents by ELISA and HPLC–DAD showed good correlation ( R=0.96, p<1×10 −10). The application of the anti-microcystin-LR antibodies for the detection and quantification of microcystins and nodularin in environmental water samples is discussed.

Isolation and Characterization of Microcystins, Cyclic Heptapeptide Hepatotoxins from a Lake Erie Strain of Microcystis aeruginosa

Cyanobacteria (blue-green algae) dominated by Microcystis aeruginosa were detected in phytoplankton samples collected from several sites in the western basin of Lake Erie during the summer of 1996 and one site in 1995. Toxin content of the samples was measured using ELISA and found to be equivalent to as much as 1 μg microcystin/L. Microcystins are potent liver toxins and tumor promoters produced by several genera of cyanobacteria. The Lake Erie M. aeruginosa colony strain (LE-3) was isolated and cultured to characterize chemically the specific microcystins (MCYSTs) present. Structures were assigned based on analytical high performance liquid chromatography (HPLC) retention times, amino acid analyses, and mass spectrometric data, revealing the leucine-arginine analog, microcystin-LR as the predominant product.

BIOCHEMICAL COMPOSITION AND FATTY ACID CONTENT OF FILAMENTOUS NITROGEN‐FIXING CYANOBACTERIA

The biochemical composition and fatty acid content of twelve strains of filamentous, heterocystous, nitrogen‐fixing cyanobacteria have been determined. When grown under diazotrophic conditions, protein, carbohydrate, lipid, and nucleic acids comprised 37–52%, 16–38%, 8–13%, and 8–11% of the dry weight, respectively. The presence of a combined nitrogen source resulted in an increase in the protein content of the cells and a decrease in the levels of lipids and carbohydrates, although biomass productivity was not affected significantly. Biochemical composition also changed during culture growth, with the highest levels of proteins and lipids occurring as the culture entered stationary phase, whereas the highest levels of carbohydrate and nucleic acids were found during the exponential phase. Total fatty acid levels in the strains assayed ranged between 3 and 5.7% of the dry weight. With regard to fatty acid composition, all strains showed high levels of polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SAFAs), with values of 24–45% and 31–52% of total fatty acids, respectively, whereas the levels of monounsaturated fatty acids (MUFAs) were in general lower (11– 32%). Palmitic acid (16:0) was the most prevalent SAFA, whereas palmitoleic (16:1n‐ 7) and oleic acid (18:1n‐9) were the most abundant MUFAs in all the strains. Among PUFAs, γ‐linolenic acid (GLA, 18:3n‐6) was present at high levels (18% of total fatty acids) in Nostoc sp. (Chile) and at lower levels (3.6% of total fatty acids) in Anabaenopsis sp. The presence of GLA has not been previously reported in these genera of cyanobacteria. The rest of the strains exhibited high levels (12–35% of total fatty acids) of α‐linolenic acid (ALA, 18:3n‐3). Linoleic acid (18:2n‐6) was also present at a substantial level in most of the strains. Eicosapentaenoic acid (EPA, 20:5n‐3) was also detected in Nostoc sp. (Albufera). Some filamentous nitrogen‐fixing cyanobacteria therefore represent potential sources of commercially interesting fatty acids.

Gaseous hydrocarbons associated with black layer induced by the interaction of cyanobacteria and Desulfovibrio desulfuricans

Black layer is a condition of high-sand-content golf greens that results in a subsurface blackened layer in the sand produced by sulfate-reducing bacteria. Black layer can be the product of an interaction of cyanobacteria and sulfate-reducing bacteria and may or may not be toxic to the grass growing on the sand. The organic byproducts of the cyanobacteria coat and plug the sand thereby creating an anoxic environment for development of the sulfate- reducing bacteria. The present study was initiated to determine the range of gaseous hydrocarbons evolved from black layered sand produced by the interaction of two genera of cyanobacteria, Nostoc and Oscillatoria, and Desulfovibrio desulfuricans. The gaseous hydrocarbons measured included methane, ethane, ethylene, and propylene. In nonblackened sand, Nostoc evolved the highest levels of these gases, Oscillatoria evolved relatively low levels except for propylene, and D. desulfuricans evolved the smallest quantities of the gases. When the cyanobacteria and D. desulfuricans were combined to develop black layered sand some changes occurred in the evolution of the gases. Evolution of the gases from Nostoc + D. desulfuricans decreased or remained the same relative to Nostoc alone, and increased relative to D. desulfuricans alone. Except for propylene evolution, gases from Oscillatoria + D. desulfuricans increased relative to Oscillatoria or D. desulfuricans alone. Propylene evolution from Oscillatoria + D. desulfuricans remained unchanged relative to Oscillatoria alone, but increased relative to D. desulfuricans alone. The gases measured are discussed relative to the organisms observed and the conditions of the study.

Spatial and temporal distribution of tropical phytoplankton species and biomass in the Gulf of Carpentaria, Australia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 118:255-266 (1995) - doi:10.3354/meps118255 Spatial and temporal distribution of tropical phytoplankton species and biomass in the Gulf of Carpentaria, Australia Burford, M. A., Rothlisberg, P. C., Wang, Y. The biomass and species composition of tropical phytoplankton in Albatross Bay, Gulf of Carpentaria, northern Australia, were examined monthly for 6 yr (1986 to 1992). Chlorophyll a (chl a) concentrations were highest (2 to 5.7 ug l-1) in the wet season at inshore sites, usually coinciding with low salinities (30 to 33 ppt) and high temperatures (29 to 32*C). At the offshore sites chl a concentrations were lower (0.2 to 2 ug l-1) and did not vary seasonally. Nitrate and phosphate concentrations were generally low (0 to 3.68 uM and 0.09 to 3 uM for nitrate and phosphate respectively), whereas silicate was present in concentrations in the range 0.19 to 13 uM. The phytoplankton community was dominated by diatoms, particularly at the inshore sites, as determined by a combination of microscopic and high-performance liquid chromatography (HPLC) pigment analyses. At the offshore sites the proportion of green flagellates increased. The cyanobacterium genus Trichodesmium and the diatom genera Chaetoceros, Rhizosolenia, Bacteriastrum and Thalassionema dominated the phytoplankton caught in 37 um mesh nets; however, in contrast to many other coastal areas studied worldwide there was no distinct species succession of the diatoms and only Trichodesmium showed seasonal changes in abundance. This reflects a stable phytoplankton community in waters without pulses of physical and chemical disturbances. These results are discussed in the context of the commercial prawn fishery in the Gulf of Carpentaria and the possible effect of phytoplankton on prawn larval growth and survival. Tropical phytoplankton . Biomass . Community . Seasonal changes . Gulf of Carpentaria Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 118. Publication date: March 09, 1995 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 1995 Inter-Research.

Use of a colorimetric protein phosphatase inhibition assay and enzyme linked immunosorbent assay for the study of microcystins and nodularins

Microcystins and nodularins are cyclic peptide hepatotoxins and tumor promoters produced by several genera of cyanobacteria. Using a rabbit anti-microcystin-LR polyclonal antibody preparation, the cross-reactivity with 18 microcystin and nodularin variants was tested. A hydrophobic amino acid, 3-amino-9-methoxy-10-phenyl-2,6,8-trimethyl-deca-4(E),6(E)-dienoic acid (Adda), which has the (E) form at the C-6 double bond in both microcystin and nodularin, was found essential for these toxins to express antibody specificity. Modification of -COOH in glutamic acid of microcystin and nodularin did not alter their antigenicity. Antibody cross-reactivity of these toxins was compared with their ability to inhibit protein phosphatase type 1 (PP1). Detection of PP1 inhibition was done by measuring the inhibition effect of the toxins on p-nitrophenol phosphate activity toward PP1. PP1 was obtained as recombinant PP1 expressed in E. coli. The inhibition effect of five microcystins and two nodularins on recombinant PP1 activity toward p-nitrophenol phosphate was measured in a microwell plate reader. The concentration of microcystin-LR causing 50% inhibition of recombinant PP1 activity (ic50) was about 0.3nM, while that of two modified microcystins had a significantly higher ic50. Microcystin-LR and nodularin with the (z) form of Adda at the C-6 double bond or having the monoester of glutamic acid did not inhibit PP1. These three toxins were also nontoxic in the mouse bioassay. These results show the importance of Adda and glutamic acid in toxicity of these cyclic peptides and that PPI inhibition is related to the toxins' mechanism of action.

Massenentwicklung von Nostoc cf. microscopicum (CARMICHAEL) Harvey ex Bornet & Flahault in alkalischem, salzhaltigem Milieu einer Höhle in den Drakensbergen Südafrikas (Golden Gate Highlands National Park)

Summary We report about an unusual mass development of the cyanobacterium Nostoc microscopicum in a 25 m deep cave in Clarens-sandstone (Karoo-system, Stormberg formation) of the Drakensberg mountains, South Africa. Besides N. microscopicum , several other genera of cyanobacteria ( Chroococcus, Gloeocapsa, Nostoc, Oscillatoria ) occurred, but were less abundant. Numerous diatoms of the genera Cymbella, Denticula and Nitzschia were also present within a gelatinous matrix on the surface of the rock. Seepage water, coming from the wall and the ceiling at the back of the cave is the only source of water. The pH of the water, as well as pH of the rock, showed strongly alkaline values (9-9.2). The growth environment of N. microscopicum and the diatoms is, to some extent, comparable to that found in soda-lakes or the so called SodiumSolontschak, a salt containing, alkaline soil type. N. microscopicum was isolated and kept in culture for taxonomical studies, which will be discussed in this paper.

The homologies of gas vesicle proteins.

In addition to GvpA, the main structural protein, an SDS-soluble protein has been found in gas vesicles isolated from six different genera of cyanobacteria. N-terminal sequence analysis of the first 30 to 60 residues of the gel-purified proteins showed that they were homologous to GvpC, a protein that strengthens the gas vesicle in Anabaena flos-aquae. The proteins from some of the organisms showed rather low homology, however, and this may explain why the genes that encode them have not been found by Southern hybridization studies. The gas vesicles of another cyanobacterium, Dactylococcopsis salina, contained two SDS-soluble proteins (M(r) 17,000 and 35,000) that were identical in sequence for the first 24 residues but not thereafter; these two proteins showed no clear homology to GvpC. The sequence of GvpA, the main structural gas vesicle protein, was very similar in each of the organisms investigated. GvpA from the purple bacterium Amoebobacter pendens was different for the first 8 residues but 51 of the next 56 residues were identical to those of the cyanobacterial GvpA. Analysis of the GvpA and GvpC sequences provides support for the idea that the low diversity of GvpA reflects a high degree of conservation rather than a recent origin followed by lateral gene transfer between different bacteria.

Effects of physical factors on the survival and growth of antarctic terrestrial algae

The survival and growth of four genera of cyanobacteria and microalgae isolated from Antarctic fellfield soils were investigated. Survival of freezing and desiccation were studied by vital staining, and the effects of photon flux density (PFD) and temperature on growth rates were determined by direct counts of cultures maintained on a thermogradient bar. Monitoring of seasonal changes in environmental factors in a fellfield ecosystem demonstrated that the experiments were carried out under ecologically relevant conditions. The coccoid chlorophyte Planktosphaerella exhibited the highest growth rates under most conditions. Growth rates of the other species were similar to each other, although the diatom Pinnularia maintained near-maximum growth rates over a wider range of conditions than the filamentous cyanobacterium Phormidium or the filamentous chlorophyte Zygnema. Maximum growth of all species occurred at 15–20°C and no growth was observed at 0°C, indicating that there is little adaptation to growth at low temperature. Optimal PFD was generally 100–400 μmol m-2 s-1 and photoinhibition of growth occurred at a PFD significantly lower than that incident on the soil surface, even on cloudy days. Such results are consistent with the observation that the soil flora largely occurs beneath the surface of the soil where PFD is reduced. All species survived repeated 24 h freeze-thaw cycles, following an initial decline on the first cycle. Survival of desiccation differed markedly between species, from a few hours in Planktosphaerella to many weeks in Phormidium and Pinnularia, and is probably a major factor in the ability of these genera to colonize the fellfield soils.

Homology of Gas Vesicle Proteins in Cyanobacteria and Halobacteria

Continuous N-terminal amino acid sequences between 26 and 64 residues long were determined for the gas vesicle protein (GVP) isolated from four genera of cyanobacteria and two species of halobacteria. Definite homology was established between the GVPsof all six organisms. Within the cyanobacteria the homologies varied from 98% to 85% with the order of decreasing similarity to Anabaena being Aphanizomenon, Oscillatoria, and Dactylococcopsis, in agreement with phylogenetic affinities. (Further homologies were also established between sequences at the C-terminus of GVP from Anabaena and Microcystis.) In the GVP from Halobacterium there was a short non-homologous sequence near the N-terminus followed by 39 residues showing 70% homology with GVP from Anabaena, and 79% with that from the halophilic Dactylo-coccopsis. An antibody raised against the Anabaena gas vesicles was effective in agglutinating gas vesicles from five different cyanobacteria, Microcyclus (a colourless eubacterium), the two halobacteria and Methanosarcina (another archaebacterium). The origin of the gas vesicle is discussed.

A carotenoid-protein from cyanobacteria

Easily solubilized carotenoid-containing proteins have been found in aqueous extracts from three genera of cyanobacteria. The three proteins have been purified, and the absorption spectra have been determined to be virtually identical with absorption maxima at 495 and 465 nm. During the purification the orange protein spontaneously changed to a red protein with a single, broad absorption maximum at 505 nm. The orange protein showed a molecular weight of 47 000 on gel filtration while that of the red protein was 26 700. Sodium dodecyl sulfate polacrylamide gel electrophoresis indicated a single polypeptide of M r 16 000 in both the red and orange forms, but this method removed the chromophore from the proteins. The main carotenoid component of the complex was determined to be 3′-hydroxy-4-keto-ββ-carotenoid or 3′-hydroxyechinenone. The number of carotenoid molecules per molecule of orange protein of molecular weight 47 000 was between 20 and 40. The stoichiometry of carotenoid to protein seemed reasonably constant.