The interactions between Chlorella vulgaris and algal symbiotic bacteria under photoautotrophic and photoheterotrophic conditions

A Chlorella vulgaris ATCC 13482 culture was semi-continuously cultivated for 18 months in a 4-L photobioreactor and formed associated consortia with other symbionts. Three symbiotic bacterial strains were isolated on heterotrophic medium agar plates. Based on 16S rDNA analysis, they were found to show closest similarity to Pseudomonas alcaligenes, Elizabethkingia miricola and Methylobacterium radiotolerans. C. vulgaris was co-cultured with each bacterial strain, and it was found that the symbiotic bacterium Pseudomonas sp. had a growth-promoting effect on C. vulgaris while the other two inhibited algal growth. The interactions between C. vulgaris and Pseudomonas sp. were further investigated under different cultivation conditions. The co-culture resulted in 1.4 times greater algal cell concentration than that of C. vulgaris alone under photoautotrophic condition. In contrast, the algal cell concentration was lower in the co-culture compared with single algal culture when glucose was supplied in the medium (photoheterotrophic). Under both cultivation conditions, the number of Pseudomonas sp. increased at the beginning of experiment, and then decreased. However, the bacterial number decreased to almost zero under photoheterotrophic conditions, while the growth of bacteria went into a stationary phase under photoautotrophic conditions. The chlorophyll content in C. vulgaris cell was higher in co-culture than in single algal culture. Algal cells in photoautotrophic condition showed higher photosynthetic efficiency compared to those in photoheterotrophic condition. Extracellular organic carbon dissolved in the medium continuously increased under photoautotrophic condition. The mutualistic and competing relationships between C. vulgaris and symbiotic bacteria observed in this study could aid our understanding of algae–bacteria interactions in nature as well as broadening its practical applications.     

Occurrence of sucrose and sucrose metabolizing enzymes in achlorophyllous algae

The presence of sucrose and the enzymes related to sucrose metabolism, i.e. sucrose synthase (SS) (UDP-glucose: D-fructose-2-glucosyl transferase, EC 2.4.1.13), sucrose phosphate synthase (SPS) (UDP-glucose: D-fructose-6-phosphate-2-glucosyl transferase, EC 2.4.1.14) and invertase (β-D-fructofuranoside fructohydrolase, EC 3.2.1.26) was demonstrated in Prototheca zopfii, a colorless alga. The levels of enzyme activities were lower than those obtained in Chlorella vulgaris, which is generally considered the photosynthetic counterpart of P. zopfii. Whem enzyme activities were measured in bleached cells of C. vulgaris, the levels were of the same order than those found in P. zopfii. These results would indicate that the sucrose metabolizing enzymes are not related to the algae ability to carry on photosynthesis.     

Promising microbial consortia for producing biofertilizers for rice fields

Two cyanobacterial cultures from rice paddies of Kyzylorda Provence, Kazakhstan were isolated and characterized: Anabaena variabilis and Nostoc calsicola. Based on these cultures, new consortia of cyanobacteria, microalgae and Azotobacter were developed: ZOB-1 (Anabaena variabilis, Chlorella vulgaris, and Azotobacter sp.) and ZOB-2 (Nostoc calsicola, Chlorella vulgaris, and Azotobacter sp.). High growth rate and photosynthetic activity of microalgae were observed in these consortia. The active consortium ZOB-1 was selected, which improved germination and growth of rice plants. ZOB-1 was recommended as a biostimulator and biofertilizer for crops.     

Storage glucan biosynthesis in Cyanidium, Chlorella and Prototheca: evidence for endosymbiosis?

The storage glucans of Chlorella pyrenoidosa and Prototheca zopfii are identical and consist of a linear polyglucan akin to amylose and a branched amylopectin component. The branched glucans of these algae differ markedly from that formed by the hot-springs alga, Cyanidium caldarium. The more highly branched Cyanidium glucan appears to be formed by branching glucosyltransferases which are different from those of the other two algae. The relevance of the data to the possibility of Cyanidium being a Prototheca-like Chlorella that has acquired symbiotic Cyanobacteria as chloroplasts is discussed.     

Algae as Bio-fertilizers: Between current situation and future prospective

Bio-fertilization is a sustainable agricultural practice that includes using bio-fertilizers to increase soil nutrient content resulting in higher productivity. Soil micro-flora has been exposed to improve soil fertility and increase biomass productivity and identified as a correct environmentally friendly bio-based fertilizer for pollution-free agricultural applies. The majority of cyanobacteria can fix nitrogen from the atmosphere and several species including Anabaena sp., Nostoc sp., and Oscillatoria angustissima is known to be effective cyanobacterial based bio fertilizers. Acutodesmus dimorphus, Spirulina platensis Chlorella vulgaris, Scenedesmus dimorphus, Anabaena azolla, and Nostoc sp. are some of the green microalgae and cyanobacteria species that have been successfully used as bio fertilizers to boost crop growth. Also, Chlorella vulgaris is one of the most commonly used microalgae in bio fertilizer studies. The addition of seaweed species that are Sargassum sp. and Gracilaria verrucosa leads to chemical changes as a soil fertility indicator on clay and sandy soils, and the addition of seaweed conditioner to soil can improve its organic content, return pH to normal, and reduce C/N ratio in both sandy and clay soil. This review provides an effective approach to increase soil fertility via environmentally friendly bio-based fertilizer using micro and macro algae. Instead of the usage of inorganic and organic fertilizers that have polluted impacts to soil as aggregation of heavy metals, in addition to there their human carcinogenic effects.     

Biological activity of l-2-azetidinecarboxylic acid,isolated from Polygonatum odoratum var. pluriflorum, against several algae

The biological activities of an aqueous fraction extracted from Polygonatum odoratum var. pluriflorum Owhi and of l-2-azetidinecarboxylic acid (AZC), purified from the extract, on the growth of several types of algae were tested. The aqueous fraction was prepared by methanol extraction of P. odoratum var. pluriflorum rhizomes followed by reverse partitioning with butanol. The aqueous extraction inhibited growth of the green alga Chlorella vulgaris by less than 10% at a concentration of 1000 mg L⁻¹. However, growth of the blue-green alga Microcystis aeruginosa was inhibited by 22.0%, 67.9%, and 87.1%, respectively, at 3.1, 6.2, and 12.5 mg extract L⁻¹. AZC was isolated from the aqueous extract and was shown to be the major active substance inhibiting algal growth. AZC concentrations higher than 25 μM inhibited growth, while at 400 μM, growth of the green algae C. vulgaris and Scenedesmus spp. was inhibited by 71.2% and 70.4%, respectively. In contrast, growth of the blue-green algae Anabaena affinis and M. aeruginosa was inhibited at concentrations greater than 1.6 and 0.2 μM, respectively, whereas 92% control required concentrations of 6.3 and 1.6 μM, respectively. AZC also suppressed the growth of the red-tide microalga Cochlodinium polykrikoides by 86.9% and 100% at concentrations of 6.3 and 12.5 μM, respectively. Azetidine and 2-azetidinone showed little activity on the tested algae. The results demonstrate that AZC selectively inhibits algal growth at low concentrations. The green algae C. vulgaris and Scenedesmus spp. were tolerant, whereas M. aeruginosa, A. affinis, and C. polykrikoides were relatively sensitive. Thus, extract and AZC, prepared from P. odoratum rhizomes, showed a potential as natural selective algicide for the control of harmful algae in laboratory assay.     

Low molecular weight carbohydrates in Cyanidium caldarium and some related algae

Floridoside (2-O-glycerol-α-d-galactopyranoside) and a small amount of iso-floridoside (1-O-glycerol-α-d- galactopyranoside) were found in Cyanidium caldarium. Floridoside was also found in the red algae Porphyridium cruentum and Porphyra yezoensis, although in the latter iso-floridoside was the main component. Sucrose and glucose were found in the green algae Chlorella pyrenoidosa and Scenedesmus obliquus, and also in a blue-green alga, Anacystis nidulans. Another blue-green alga, Phormidium foveolarum, contains mostly trehalose. From these results and from morphological considerations, it is suggested that Cyanidium caldarium belongs to the primitive Rhodophyta.     

The toxicity of phenolic compounds to soil algal population and toChlorella vulgaris andNostoc linckia

Summary p-Nitrophenol (PNP),m-nitrophenol (MNP), 2,4-dinitrophenol (DNP) and catechol were tested for their effects on algal population in a soil and on pure cultures of two algae isolated from soil. Both PNP and MNP, even at 0.5 kg ha⁻¹ level were toxic to the soil algae; high doses effected increase in toxicity. Inhibition of algae was relatively more with PNP compared to the other two nitrophenols. Catechol treatment up to 1.0 kg ha⁻¹ led to a significant initial enhancement of algae with a subsequent far less toxic effect. The toxicity of the phenolic compounds towardChlorella vulgaris, a green alga andNostoc linckia, a blue-green alga, decreased in the order: MNP≧PNP>DNP>Catechol. However, algicidal or algistatic effect of the test chemicals was fairly more againstC. vulgaris, suggesting that the eukaryotic alga is highly sensitive to such soil pollutants compared to the prokaryotic alga.     

Molecular Evolution of Lycopene Cyclases Involved in the Formation of Carotenoids in Eukaryotic Algae

Carotenoids play crucial roles in structure and function of the photosynthetic apparatus of bacteria, algae, and higher plants. The formation of carotenoids from lycopene is catalyzed by the enzyme lycopene cyclase (LCY), which is structurally and functionally conserved in all organisms. A comparative genomic analysis regarding the LCY revealed that the higher plant (Arabidopsis thaliana) and the green alga (Ostreococcus sp. RCC809, Ostreococcus tauri, Ostreococcus lucimarinus, Micromonas sp. RCC299, Micromonas pusiua, Chlorella vulgaris, Volvox carteri, and Coccomyxa sp. C-169) possess two different LCY (beta- and epsilon-type). This indicated that an ancient gene duplication event must have occurred, which produced two classes of LCY in algae. However, some other green alga retained only one class of LCY, such as Haematococcus pluvialis (beta), Dunaliella salina (beta), Chlamydomonas reinhardtii (epsilon), and Chlorella sp. NC64A (epsilon), and the other gene copy was lost in these species. Furthermore, the similar LCY lost occurred in red alga (Cyanidioschyzon merolae) and Heterokontophyta (Phaeodactylum tricornutum and Thalassiosira pseudonana), which possess only the LCYB. In addition, the protein sequence of LCYB is highly similar to capsanthin–capsorubin synthase (CCS), which is another carotenogenic enzyme of plants. As a result, it is proposed that the CCS evolved from a duplicated LCYB. The discovery of two classes of LCY families in some algae suggests that carotenoid biosynthesis is differentially regulated in response to development and environmental stress in these algae, like members of LCY families are differentially regulated during development or stress in some higher plants.     

Effets du cuivre sur l'ultrastructure de Scenedesmus quadricauda et Chlorella vulgaris. Effect of copper on the ultrastructure of Scenedesmus quadricauda and Chlorella vulgaris

A laboratory investigation was conducted to study the effect of various concentrations of copper on the freshwater algae Scenedesmus quadricauda and Chlorella vulgaris. Electron-dense inclusions were observed in the vacuoles of S. quadricauda, and this alga showed some growth at a dose as high as 2,500 μg.1⁻¹. The occurrence of the electron-dense inclusions was correlated significantly with the copper concentration and seems to be implicated in the tolerance of the species. C. vulgaris was much more sensitive to copper than S. quadricauda and showed osmotic changes and membrane damage.     

EFFECTS OF HYDROXAMATE SIDEROPHORES (STRONG Fe (III) CHELATORS) ON THE GROWTH OF ALGAE1

Varying concentrations of Fe were tested with three hydroxamate siderophores to demonstrate the interactions affecting growth of Chlamydomonas reinhardtii and Chlorella vulgaris. Schizokinen was purified from the excretions of the blue-green alga Anabaena sp. grown in low-Fe medium. Chlamydomonas reinhardtii was inhibited by schizokinen when in molar excess of the Fe concentration; the inhibition was overcome with excess Fe. The growth of C. vulgaris was not affected by this chelator. Results with desferrioxamine were similar. A weaker chelator, rhodorulic acid, did not inhibit the growth of either alga. Low concentrations of the chelators may stimulate algal growth when Fe precipitates are hydrolyzed. Since different algae respond differently to the presence of the chelators, the observed interactions could be important in determining competitive relationships when Fe is limiting. If an alga can excrete a strong chelating agent, as does Anabaena, algae lacking the ability to compete with the chelator may not grow.     

Bioprospecting for oil producing microalgal strains: evaluation of oil and biomass production for ten microalgal strains

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20-50% of dry weight) of lipids. A successful and economically viable algae based oil industry depends on the selection of appropriate algal strains. In this study ten species of microalgae were prospected to determine their suitability for oil production: Chaetoceros gracilis, Chaetoceros mulleri, Chlorella vulgaris, Dunaliella sp., Isochrysis sp., Nannochloropsis oculata, Tetraselmis sp., Tetraselmis chui, Tetraselmis tetrathele and Thalassiosira weissflogii. The study was carried out in 3 L glass flasks subjected to constant aeration and controlled artificial illumination and temperature at two different salinities. After harvesting, the extraction of oil was carried out using the Bligh and Dyer method assisted by ultrasound. Results showed that C. gracilis presented the highest oil content and that C. vulgaris presented the highest oil production.     

Oil production by six microalgae: impact of flocculants and drying on oil recovery from the biomass

Oil production in batch photoautotrophic cultures of the following microalgae is reported: the freshwater microalgae Chlorella vulgaris, Choricystis minor, and Neochloris sp.; the marine microalgae Nannochloropsis salina and Cylindrotheca fusiformis; and C. vulgaris grown in a full-strength seawater medium. In all cases, the solvent extraction of lipids from freeze-dried biomass is compared with extraction from the fresh biomass paste. For all algae, the oils could be extracted equally effectively from freeze-dried samples and the paste samples (67–88 % moisture by weight). Moisture content determinations of the biomass using the freeze-drying method and the high-temperature oven drying were found to be equivalent for all algae. The biomass recovered by flocculation with metal salts (aluminum sulfate, ferric chloride) followed by centrifugation had a certain amount of the flocculant irreversibly bound to it. Washing failed to remove the adsorbed flocculants. For all algae, the adsorbed flocculants did not interfere with oil recovery by solvent extraction. The solvent system of chloroform–methanol–water proved highly effective for quantitative extraction of the lipids from all algae.     

The circadian rhythm in Bryophyllum leaves: Phase control by radiant energy

An inactivated nitrate reductase (EC 1.6.6.1) formed in vivo by the green alga Chlorella fusca Shihira and Kraus is shown to be a cyanide complex. The partially purified inactive enzyme releases 0.048 nmol of HCN per unit of enzyme activated. This compares with 0.066 nmol of HCN liberated in similar previous measurements with the inactivated enzyme from Chlorella vulgaris. The nitrate reductase from C. fusca has been purified to a level of 67 mol nitrate reduced per min per mg enzyme. It contains a cytochrome b₅₅₇, at a level 1.9-fold higher per unit of active enzyme, than the nitrate reductase from C. vulgaris.Abbreviations FAD flavin-adenine dinucleotide - NADH nicotineamide-adenine-dinucleotide (reduced)     

The cell content and secretion of water-soluble vitamins by several freshwater algae

Three green algae, Chlamydomonas reinhardii, Chlorella vulgaris and Scenedesmus obliquus, and one blue-green alga, Anabaena cyclindrica, were grown in chemically defined media. All the algac examined contained folates, -carotene and vitamins C and E; several of the B-vitamins and vitamin A were found in varying amounts in some but not in all the algae examined. All the green algae secreted significant amounts of folate and biotin and all but Scenedesmus secreted pantothenate into their growth medium; Anabaena secreted folate and pantothenate.This work was done with the support of grant BMS 74-08918 from the National Science Foundation     

Ensifer shofinae sp. nov., a novel rhizobial species isolated from root nodules of soybean (Glycine max)

Two bacterial strains isolated from root nodules of soybean were characterized phylogenetically as members of a distinct group in the genus Ensifer based on 16S rRNA gene comparisons. They were also verified as a separated group by the concatenated sequence analyses of recA, atpD and glnII (with similarities ≤93.9% to the type strains for defined species), and by the average nucleotide identities (ANI) between the whole genome sequence of the representative strain CCBAU 251167^T and those of the closely related strains in Ensifer glycinis and Ensifer fredii (90.5% and 90.3%, respectively). Phylogeny of symbiotic genes (nodC and nifH) grouped these two strains together with some soybean-nodulating strains of E. fredii, E. glycinis and Ensifer sojae. Nodulation tests indicated that the representative strain CCBAU 251167^T could form root nodules with capability of nitrogen fixing on its host plant and Glycine soja, Cajanus cajan, Vigna unguiculata, Phaseolus vulgaris and Astragalus membranaceus, and it formed ineffective nodules on Leucaena leucocephala. Strain CCBAU 251167^T contained fatty acids 18:1 ω9c, 18:0 iso and 20:0, differing from other related strains. Utilization of l-threonine and d-serine as carbon source, growth at pH 6.0 and intolerance of 1% (w/v) NaCl distinguished strain CCBAU 251167^T from other type strains of the related species. The genome size of CCBAU 251167^T was 6.2 Mbp, comprising 7,581 predicted genes with DNA G+C content of 59.9 mol% and 970 unique genes. Therefore, a novel species, Ensifer shofinae sp. nov., is proposed, with CCBAU 251167^T (=ACCC 19939^T = LMG 29645^T) as type strain.     

INHIBITION OF PHOTOSYNTHESIS IN ALGAE BY DIMETHYL SULFOXIDE1

Photosynthetic oxygen evolution and ¹⁴CO₂ fixation by 3 blue-green algae, Anabaena flos-aquae, Oscillatoria sp., and Anacystis nidulans, and 1 green alga, Chlorella pyrenoidosa, were: inhibited by dimethyl sulfoxide at concentrations above 1%.