Nostoc (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Nostoc sphaericum - 1. habit of mature thalli. N. commune - 2, detail of filaments in gelatinous thallus; var. flagelliforme - 3, habit. N. verrucosum - 4, cross-section of a gelatinous thallus; 5, details of filaments in gelatinous thallus. N. linckia - 6, detail of filaments in gelatinous thallus. N. muscorum - 7, detail of filament.

Nostoc Vaucher ex Bornet & Flahault

Protologue: Révis. Nostoc. hét.: 181 (1886) [1888].

Family: Cyanophyceae

Chromosome number: Prokaryotic, thus no chromosomes

Major species and synonyms

• Nostoc commune Vaucher ex Bornet & Flahault, Révis. Nostoc. hét.: 203 (1886) [1888], incl. var. commune and var. flagelliforme Berk. & M.A. Curtis ex Bornet & Flahault, Révis. Nostoc. hét.: 206, synonym of latter var.: N. flagelliforme Berk. & M.A. Curtis ex Bornet & Flahault (1886).

• Nostoc linckia (Roth) Bornet & Thur. ex Bornet & Flahault, Révis. Nostoc. hét.: 192 (1886) [1888], synonym (Drouetian): Calothrix parietina (Nägeli) Thur. ex Bornet & Flahault (1886).

• Nostoc microscopicum Carmich. ex Bornet & Flahault, Révis. Nostoc. hét.: 210 (1886) [1888], synonym (Drouetian): Nostoc commune Vaucher ex Bornet & Flahault (1886) [1888].

• Nostoc muscorum C. Agardh ex Bornet & Flahault, Révis. Nostoc. hét.: 200 (1886) [1888], synonym (Drouetian): N. commune Vaucher ex Bornet & Flahault (1886) [1888]. * Accepted name is now (2016): Desmonostoc muscorum (C.Agardh ex Bornet & Flahault) Hrouzek & Ventura (2013).

• Nostoc verrucosum Vaucher ex Bornet & Flahault, Révis. Nostoc. hét.: 216 (1886) [1888], synonym (Drouetian): N. commune Vaucher ex Bornet & Flahault (1886) [1888].

Vernacular names

• Star jelly, witches' butter, mares' eggs (En)
• Indonesia: jamur batu (Java)
• Philippines: tabtaba (= Nostoc linckia). China: fah-tsai or facai. Japan: ishikurage.

Origin and geographic distribution

Nostoc has a cosmopolitan distribution. These common terrestrial and sub-aerial algae can be found in alkaline soils, especially in rice fields, and on moist rocks and cliffs. Occasionally they occur in marine waters or in brackish habitats, such as salt marshes and mangrove swamps. Nostoc-containing lichens can be dominant primary producers in some areas.

Uses

N. commune is collected in moist hilly locations of the Ilocos region in the Philippines and eaten as green salad. Some other Nostoc spp. (N. linckia, N. microscopicum) are also collected in the same area. In Thailand N. verrucosum is used for food. The marine form of N. commune, var. flagelliforme, is collected for food in China, Japan and Java (Indonesia). The dried algae are cooked with noodles, vegetables and mushrooms, and served as a vegetarian dish or a soup by the Chinese. They often serve it as a New Year's dish. In paddy soils, the ability of Nostoc to fix atmospheric nitrogen increases the nitrogen content of those soils, and thus may increase rice yields. The blue-green algae living in the water fern Azolla Lamk may belong to the genus Nostoc, although they are usually considered to be Anabaena spp. Nostoc colonies can be a nuisance on sport turfs, as they make them very slippery.

Production and international trade

Dried N. commune var. flagelliforme is exported from China to Malaysia, Singapore, Hong Kong and Taiwan, but data on international trade are not available.

Properties

Per 100 g dry weight N. commune contains: protein 39.9 g, lipids 5.0 g, carbohydrates 5.5-6.1 g and ash 24.3-27.5 g. The major essential amino acids (% of total protein) include leucine (6.7-9.2%), valine (7.1-9.2%), threonine (6.0-7.8%) and phenylalanine (5.5-7.2%). The dominant fatty acids (% of total fatty acids) are 16:0 (23-33%), 16:1 (10-18%), 18:1 (17-28%), 18:2 (4-18%) and 18:3 (3-28%).

Per g dry weight it contains the following pigments: phycobiliproteins 89 mg, chlorophyll a 1.8-2.7 mg and carotenoids 0.37-0.53 mg. The composition of the phycobiliproteins (% of total content) is as follows: phycocyanin (58%), allophycocyanin (25%) and phycoerythrin (19%). The carotenoids consist of β carotene (39%), zeaxanthin (10%), echinenone (17%), canthaxanthin (7%), caloxanthin (8%), nostoxanthin (7%) and myxoxanthophyll (8%).

The nitrogen fixation rate on the basis of acetylene reduction activity ranges between 567-1090 nM C₂H₄g/h.

Phenolic extracts from N. muscorum have fungicidal and bactericidal properties. These inhibit mycelial development of the soil-borne phytopathogenic fungus Cunninghamiella blakesleana. Another species, N. ellipsosporum (Desm.) Rabenh. ex Bornet & Flahault, contains a bioactive compound cyanovirin. This irreversibly inactivates the HIV virus without adversely affecting the host cells. Work on this compound is being actively pursued.

Description

Plants with mucilaginous, gelatinous or coriaceous thalli; thalli first globose to oblong, later globose, foliose, filiform, bullate, lobed, or warty, solid or hollow, free or attached, with periphery surrounded by firm, dense and darkly coloured surface layer (pellicle); filaments flexuous, curved or entangled; sheath distinct or diffluent; trichomes torulose; cells depressed, spherical, barrel-shaped or cylindrical; heterocysts intercalary; spores spherical or oblong.

• N. commune. Thalli firm, gelatinous, at first globose, later flattened, expanding, undulated, membranous or leathery, often perforated, up to 20 cm in diameter, blue-green, olivaceous or brown; filaments flexuous, entangled; sheath mostly only distinct at the periphery, thick, yellowish-brown, often lamellated, inside the thallus hyaline; trichomes 4.5-6 μm broad, cells short barrel-shaped or nearly spherical, mostly shorter or a little longer than broad, 5 μm long; heterocysts almost spherical, about 7 μm broad; spores very rare.

• N. linckia. Thalli gelatinous, attached, young stages punctiform, tuberculate or globose, when mature more or less formless, expanding, torn, varying in size, blue-green to violet or black-green to brown; filaments densely entangled, flexuous or highly coiled; sheath diffluent, colourless inside, distinct only in peripheral portion; trichomes 3.5-4 μm broad, pale green, cells short barrel-shaped; heterocysts subspherical; spores subspherical, 6-7 μm × 7-8 μm, epispore smooth.

• N. microscopicum. Thalli soft, but with firm outer surface, attached, spherical or ellipsoidal, usually 1 cm in diameter or smaller, first glistening, later olivaceous or brown; filaments loosely entangled; sheath more or less distinct, yellowish; trichomes 5-8 μm broad, blue-green or olive-green, cells subspherical or barrel-shaped; heterocysts nearly spherical, 7 μm broad; spores oval, 6-7 μm × 9-15 μm, olivaceous, epispore smooth.

• N. muscorum. Thalli gelatinous-membranous, irregularly expanded, attached by lower surface, tuberculate, 2-5 cm in diameter, dull olive or brown; filaments densely entangled; sheath only distinct at periphery, yellowish-brown; trichomes 3-4(-5) μm broad, cells short barrel-shaped to cylindrical, up to twice as long as broad; heterocysts almost spherical, 6-7 μm broad; spores rare, oblong, many in series, 4-8 μm × (7-)8-12 μm, epispore smooth, yellowish.

• N. verrucosum. Thalli often gregarious, at first spherical or subspherical, solid, gelatinous and firm, surface undulate or verrucose, later hollow, vesicular, soft, torn, up to 10 cm in diameter, black-green, olive-green or brown-green; filaments flexuous, densely entangled at the periphery; sheath thick, at the periphery yellowish-brown, inside the thallus hyaline and diffluent; trichomes 3-3.5 μm broad, cells short barrel-shaped, shorter than broad; heterocysts subspherical, 6 μm broad; spores oval, many in series, 5 μm × 7 μm, epispore smooth and yellowish.

Growth and development

The cells of Nostoc divide by binary fission, which increases the length of the contorted trichomes. Reproduction is through the development of akinetes (spores) and by hormogonia (short, motile trichomes) as well as by fragmentation or budding of large colonies. Not all species form akinetes. In N. commune akinetes do not occur. The development of motile hormogonia forming a mature aggregate of filaments occurs entirely within a common matrix, and thus the aggregate has a fixed shape within the pellicle. This pellicle can be ruptured by the protruding hormogonia ("budding"), resulting in the formation of new colonies. The formation of motile hormogonia is promoted by red, but is blocked by green or white light. In N. muscorum and other Nostoc spp. hormogonia can form gas vesicles which probably allow the species to disperse more rapidly in flooded soils. Some strains of Nostoc are probably facultatively heterotrophic: in laboratory experiments many strains are able to grow on glucose, fructose, ribose, or sucrose.

Nostoc spp. are able to use various nitrogen sources, including inorganic nitrogen, amino acids, and atmospheric nitrogen. Several factors influence the rate of atmospheric nitrogen fixation. Activity increases at higher temperatures (up to 35°C) and decreases at low moisture levels. The addition of ammonia lowers nitrogen fixation rates, but the addition of nitrate probably has little effect.

Ecology

Optimal temperatures for growth of N. commune range between 20-30°C, while optimal pH ranges between 6.5-8.5. The alga colonies can survive desiccation for months or years and recover their metabolic activity after rehydration. During desiccation, specific proteins are synthesized, fatty acid profiles and mRNA pools are altered, and nitrogenase activity is lost. The large amount of sheath material increases the resistance of the alga to desiccation and also protects it against high light intensity and grazer attack. N. commune var. commune is a freshwater variety that occurs on moist soils, rocks and in stagnant waters, including paddy fields. N. verrucosum occurs also on moist soils and rocks, while N. linckia, N. microscopicum and N. muscorum are mainly limited to moist soils only, including paddy-field soils.

N. commune is one of the dominant algae in rice fields. The abundance of the alga is found to be significantly correlated to mean solar radiation and the amount of orthophosphate in the floodwater, but is suppressed by the addition of urea. Phosphorus and inorganic carbon generally limit productivity of Nostoc. Other elements related to maintenance of growth, photosynthesis or nitrogenase activity include boron (both for growth and nitrogenase synthesis), molybdenum (in nitrogenase and nitrate reductase) and vanadium (can partly substitute for molybdenum).

An important interaction of Nostoc with fungi is the formation of lichens. The fact that Nostoc can withstand repeated drying, is photosynthetic and is able to fix atmospheric nitrogen, makes it an ideal symbiont for fungi. Some Nostoc spp. interact symbiotically with various plants, including liverworts, hornworts, mosses, cycads, and several Angiosperms. All known Gunnera spp. support a Nostoc sp. as an endosymbiont. The Nostoc supplies fixed nitrogen to the host.

Propagation and planting

N. commune can be grown in liquid or solidified inorganic medium (2% w/v agar), either BG11 or Bold's Basal Medium. The nitrogen source can be omitted, especially if the cultures are being used for nitrogen-fixation studies. Illumination (42 μmol photon m²s¹) can be provided by fluorescent lamps (Grolux or Truelite) under a 12:12 h light-dark cycle. The cultures are non-homogenous, with the filaments forming aggregates even though they are agitated by orbital shaking.

Phycoculture

There is no commercial cultivation of N. commune. However, this is one of the species in the blue-green algal mixture cultured for use as biofertilizer in rice fields (algalization). In India, the soil-based mixture of algae is cultured in iron trays or cement tanks containing water mixed with 8-10 kg soil, 200 g superphosphate and 10 g insecticides.

Diseases and pests

Some cyanophages can infect Nostoc, but no studies have been published regarding the importance of infection in natural populations. Insecticides such as folidol (1 ppm), parathion (7.5 ppm) or carbofuran (3% granules) are added to prevent breeding of mosquitoes and other insects in the culture basin.

Harvesting

The blue-green algae for soil algalization are harvested in the form of a soil-based mixture.

Yield

In the mixed cultures of blue-green algae for soil algalization each tray or tank measuring 2 m × 1 m × 0.25 m may yield up to 1.5-2 kg of algal material; however, the percentage of biomass contributed by N. commune is not known.

Handling after harvest

After sun-drying, soil flakes containing the mixture of bluegreen algae are applied in rice fields at 8-10 kg per ha, 1 week after transplanting. N. commune thalli collected for food are either directly sold at local markets or sun-dried before transport.

Prospects

Investigations into the control of the nitrogenfixation process in N. commune, especially at the molecular level, should be intensified. This includes the search for more information on the use of Nostoc and other blue-green algae in sustainable agricultural practices. Efforts should also focus on the selection of highyielding strains. The potential of these algae as sources of fine chemicals, such as pigments and bioactive compounds (antibiotics and anti-HIV compounds), is worth exploring. Their demonstrated cholesterol-reducing ability suggests future use as nutraceutical. The possibility of growing these algae by immobilization for the photoproduction of gas should also be investigated.

Literature

• Cobelas, M.A. & Lechado, J.Z., 1989. Lipids in microalgae. A review. I. Biochemistry. Grasas y Aceites 40(2): 118-145.
• Dodds, W.K., Gudder, D.A. & Mollenhauer, D., 1995. The ecology of Nostoc. Journal of Phycology 31: 2-18.
• Emralino, G. & Rodulfo, B.R., 1987. Cultural studies on blue-green algae III. Nostoc microscopicum Carmichael. The Philippine Journal of Science 116: 67-72.
• Martinez, M.R. & Querijero, N.M.B., 1986. Macrocolony formation in the nitrogenfixing bluegreen alga, Nostoc commune Vauch. The Philippine Agriculturist 69(4B): 547-565.
• Martinez, M.R. & Querijero, N.M.B., 1986. Fate of applied bluegreen algae and their effects on the yield of wetland rice. The Philippine Agriculturist 69(4B): 611-627.
• Moreno, J., Rodriguez, H., Vargas, M.A., Rivas, J. & Guerrera, M.G., 1995. Nitrogenfixing cyanobacteria as source of phycobiliprotein pigments. Composition and growth performance of ten filamentous heterocystous strains. Journal of Applied Phycology 7: 17-23.
• Nichols, B.W., 1973. Lipid composition and metabolism. In: Carr, N.G. & Whitton, B.A. (Editors): The biology of bluegreen algae. Blackwell Scientific Publications, Oxford, United Kingdom. pp. 144-161.
• Scherer, S. & Zhong, Z.P., 1991. Desiccation independence of terrestrial Nostoc commune ecotypes (cyanobacteria). Microbial Ecology 22: 271-283.

Sources of illustration

Desikachary, T.V., 1959. Cyanophyta. ICAR Monographs on algae. Indian Council of Agricultural Research, New Delhi, India. Plate 70, fig. 1, p. 386 (N. verrucosum); Frémy, P., 1930. Les myxophycées de l'Afrique équatoriale française [The myxophyceae of French Equatorial Africa]. Archives de Botanique 3, Mémoire No 2: fig. 281, p. 341 (N. muscorum), fig. 283, p. 343 (N. commune); Frémy, P., 1934. Les cyanophycées des Côtes d'Europe [The Cyanophyta of the European coasts]. Mémoires de la Société Nationale des Sciences Naturelles et Mathématique de Cherbourg 41: plate 58 (N. linckia, N. commune var. flagelliforme), plate 59 (N. sphaericum). Redrawn and adapted by P. Verheij-Hayes.

Authors

• S.-M. Phang