MadSci Network: General Biology
Query:

Re: What are some Economic Importance of the protists

Date: Sat Mar 27 12:25:30 1999
Posted By: Dominique Dugourd, Post-doc/Fellow, Microbiology, Sunnybrook HSC
Area of science: General Biology
ID: 920519207.Gb
Message:

I must confess that I am not thrilled by this kind of question. I am always sorry when there is an ecological catastrophe to see that we are very fast to put numbers on the economical losses that will likely be faced as though it would be the only thing that will really affect the population.

There is a richess that you can't even count in economic terms, solet's see about the protist. The protists are unicellular eucaryotes. They are divided in 3 groups including fungi, algae and protozoa.

Each group has its own economical importance. Originating from France, I will start by the group I enjoy the most; fungi.

Fungi
The importance of fungi in the food industry is tremendous, just think to the cheeses that rely on them to mature and gain their particular flavours.

Yeast have a major role in the food industry in fermentation of beer and wine, and in the making of bread.

Scientific Research:
Yeast are also used as a model organism for higher cell types. Yeast are single-celled, fast growing, cheap to keep and easy to manipulate. A lot of their physiology and genetics are already known - that makes it easier to use yeast for the discovery of new drugs or as a tool to better understand the eucaryotes.

The second group is composed of the algae.

Food Industry:
Although red algae have been consumed by humans for at least 2,800 years, their full agronomic and biotechnological potential have yet to be realized. At least 344 species are considered to be of economic value, but only species of Porphyra, Gelidium, Gloiopeltis, Euchuma, and Gracilaria have been cultivated by any significant extent.

In 1999 only the production of green algae Spirulina for human consumption was 2630 metric tons. Spirulina has been marketed and consumed as a human food and has been approved as a food for human consumption by many governments, health agencies and associations of over 70 countries.

Chemical Usage:
The main chemicals commercially obtained from seaweeds are the phycocolloids. Phycocolloids are used extensively in the food, cosmetic, and pharmaceutical industries, as emulsifiers and as gelling agents. Like the extract from terrestrial plants, the pectins, they are cell wall components which are soluble in hot water and relatively insoluble in cold. Three major types of commercial phycocolloid are produced: the alginates (from members of the Phaeophyta), the carrageenans, and the agars. Their combined value is in excess of U.S. $200 million annually.

  1. Carrageenans: Carrageenans are phycocolloids obtained from members of the Hypneaceae, Phyllophoraceae, Solieriaceae, and Gigartinaceae of Rhodophyta.Carrageenan is used in the food industry as an emulsifier, particulary in dairy products; as a size in the textile and leather industries; and as an emulsifier in the pharmaceutical industry.
  2. Agar: Agar is a Malay word for the gelling substance extracted from Eucheuma, which is ironically now known to be a carrageenan. Agar is extracted from a number of species of Gelidium, and to a lesser extent from Gracilaria, Pterocladia, Acanthopeltis, and Ahnfeltia. There are two compounds; agarose and agaropectin. Aga is principally used in the preparation of high-quality bacteriological and tissue culture media. Pure agarose is now used as a gel in electrophoretic and chromatographic studies.

    The annual production is 10,000 tonnes with a value of about U.S. $ 50 million.

  3. Gelans : There are a great number of substances which, from the meagre information available, resemble kappa-carrageenan except that the degree of sulphation is much less.
Fertilizers:
Seaweeds have adequate amounts of postassium and nitrogen, but are low on phosphate. Crustose coralline algae material collected directly from the sublittoral, as in England, is the most superior fertiliser. It contains a certain quantity of nitrogenous and phosphoric substances although these do show some seasonal variation. Seaweeds also rich in trace elements and may contain hormones and growth regulators. Seaweed manures have the advantage of being free from weeds and pathogenic fungi.

Medicines:
Seaweeds have been extensively used in the traditional medicines of maritime nations as vermifuges, anaesthetics, and ointments, as well as for the treatment of coughs, wounds, gout, goitre, hypertension, venereal diseases, cancer, and a variety of other ills. The typical example is the use of Digenia simplex which contains a potent vermifuge, kainic acid. The vitamin and mineral content of marine algae also are potentially important in the prevention of other dietary insufficiency diseases.

Crude extracts of many species contain substances with antibiotic properties against bacteria, fungi, and viruses. Antiviral compounds reported in red algae include polysaccarides containing D-glycosyl groups, which are apparently active in the control of herpes viruses. They act by blocking viral attachment points on the cell membrane. Many seaweeds contain sterols and related compound, which are antagonistic to cholesterol in mammalian systems and may reduce elevated blood pressure associated with atherosclerosis.

Carrageenan may be used to induce ulceration in the stomach and intestines of animals to test anti-inflammatory compounds. It do not cause ulcers in humans and has been used in the treatment of peptic ulcers. The abilites of carrageenans and alginates to form metal salts have suggested their use as non-toxic chelating agents in the treatment of heavy metal and radionucleotide poisonings.

Soil dressing:
Several species of crustose coralline algae can occur in an unttached 'loose-lying' state, producing extensive beds in the shallow sublittoral. The coralline sand is carted for use in liming the highly acidic soils which are found along much of the European coast.

The third group is composed by the protozoaires.

I will just give details about one member of this group because of its major health related impact; Plasmodium. Plasmodium protozoa, P.falciparum, P.vivax, P. ovale and P.malarioe are the causative agents in humans of the malaria. Of these, P.falciparum accounts for the majority of infections and is the most lethal.

Malaria is a public health problem today in more than 90 countries, inhabited by a total of some 2400 million people ­­ 40% of the world's population. Worldwide incidence of the disease is estimated to be on the order of 300­500 million clinical cases each year. More than 90% of all malaria cases are in sub­Sahara Africa, with two­thirds of the remainder concentrated in six countries ­­ India, Brazil, Sri Lanka, Afghanistan, Viet Nam and Colombia, in decreasing order of prevalence. Mortality due to malaria is estimated at 1.5 to 2.7 million deaths each year.

In many developing countries, and in Africa especially, malaria exacts an enormous toll in lives, in medical costs, and in days of labour lost. Costs to countries include costs for control and lost workdays - estimated to be 1-5% of GPD in Africa

You just can't live a day without encountering protists.


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