Algae are relatively undifferentiated organisms which, unlike plants, have no true roots, leaves, flowers or seeds. They are found in marine, freshwater and terrestrial habitats. Their size varies from tiny microscopic unicellular forms of 3-10 µm (microns) to large macroscopic multicellular forms up to 70 meters long and growing at up to 50 cm per day. Algae do not have water-conducting tissues, as they are, at some stage, surrounded by water, which is also important for reproduction by spores. The spores may be motile or non-motile. Most of the algae are photosynthetic organisms that have chlorophyll. Apart from chlorophyll, they contain additional pigments, which are the basis of classification.
Phytoplankton, seaweeds and symbiotic dinoflagellates (unicellular, biflagellate organisms) in corals and sea anemones are marine algae. Seaweeds are classified as Green algae (Chlorophyta), Brown algae (Phaeophyta), Red algae (Rhodophyta) and some filamentous Blue-green algae (Cyanobacteria). Most of the seaweeds are red (6000 species) and the rest known are brown (2000 species) or green (1200 species). Seaweeds are used in many maritime countries as a source of food, for industrial applications and as a fertilizer. Nori (Porphyra spp.), a Japanese red seaweed, is very popular in the Japanese diet, has a high protein content (25-35% of dry weight), vitamins (e.g. vitamin C) and mineral salts, especially iodine. Industrial utilization is at present largely confined to extraction for phycocolloids, industrial gums classified as agars, carrageenans and alginates. Agars, extracted from red seaweeds such as Gracilaria , are used in the food industry and in laboratory media culture. Carrageenans, extracted from red seaweeds such as Chondrus, Gymnogongrus, and Eucheuma among others, are used to provide particular gel qualities. Alginates are derivatives of alginic acid extracted from large brown algae such as Laminaria. They are used in printers' inks, paints, cosmetics, insecticides, and pharmaceutical preparations. In the USA, alginates are used as stabilizers in ice cream and also as a suspending agent in milk shakes. In 1995, the estimated value of international seaweed gums market was $560 million dollars.
Northeastern University, in the United States, has filed a PCT application related to transformation of multicellular marine algae via Agrobacterium. Marine algae are defined by the applicants as non-angiosperm photosynthetic eukaryotic organisms that live in the ocean or in saline water. According to the disclosure, marine algae could serve as a source of valuable pharmaceutical compounds through genetic engineering. They naturally have a very high protein content and are easy to grow for biomass.
With respect to genetic transformation, the applicants claim to provide a stable method for genetic transformation of multicellular marine algae. The method comprises wounding the outer cell wall layer of an alga in order to facilitate the access of Agrobacterium T-DNA with a gene of interest. The transformation of algal cells takes place in an environment containing seawater to ensure the survival of the transformed algae. To exemplify their invention, the applicants describe the transformation of the red alga Porphyra, known as nori, for which worldwide production is estimated at $1.5 billion dollars annually.
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