Strengthening Development of the Science of Microscopic Organisms
Prof. Liu Zhili from the Nanjing University Institute of Life Sciences discussed the importance of strengthening the development of the science of microscopic organisms from the perspective of the 50 years he spent working in the field and observing its development and changes. Microscopic organisms are very important to basis science The appearance of bacteria and blue-green algae about 3.8 billion years ago had a profound effect on the evolution of the atmosphere, lithosphere and biosphere. Blue-green algae photosynthesis emitted oxygen into the primeval atmosphere, promoting the emergence and evolution of lithosphere and biosphere. Petroleum and natural gas were generated from palaeo-microalgae and its biomarkers, and their fossils are a key basis for comparing oil strata, determining the sediment environments, origins, abundance and quality of oil and gas. China is a nation famous for its annual petroleum production, worth about 300 billion yuan per year. Microalgae are the productive force in oceans, lakes and rivers. This productive force is six times that of terrestrial organisms. As an applied biological science, microbiology deals with many important practical problems in medicine, agriculture and industry. Some of the most serious human, animal and plant diesases are caused by microorganisms. Microorganisms play an important role in soil fertility and the formation of animal products. Many large-scale industrial processes are microbially based, and they lave led to the development of the whole new discipline of biotechnology. Algae as ecological indicators It is believed that eutrophication in lakes and seas is caused by pollution. Recent research shows that 65 percent of the lakes in our country are eutrophic. Wherever conditions of temperature, light, and nutrition are appropriate, increased growth of blue-green algae or dinoflagelletes may occur. This phenomenon is called water bloom or red tide. Some blue-green algae and dinoflagelletes may produce toxins, hepatotoxic cyclic peptides such as microcystins and nodularins. Microorganisms are an important source of nutrients and a treasure chest of human medicine Many antibiotics are acquired from actinomyces and fungi, for example, penicillin, streptomycin, chloromycetin, terramycin (oxytetracyclin), cycloheximide, amphotericin, nystatin, blasticidin and kasugamycin. There are hundreds of antifungal antibiotics, most of which are produced by a few species of Actinomycetes of the Streptomyces genus, and fungi of the Penicillium and Aspergillus genera and their close relatives. After these antibiotics were discovered, they served as effective medicines in controlling diseases in humans, domestic animals and cultivated plants. Microalgae contain more than ten vitamins, five polyunsaturated fatty acids, and many kinds of complex chemicals. Some of the vitamins that are produced by algae are of particular commercial interest, for example, vitamin B12, vitamin E(tocopherol), nicotinic acid, vitamin C(ascorbic acid), d-Ca-pantothenate, vitamin A, thiamine HCl(B1), pyridoxine(B6), riboflavin(B2), folic acid and biotin.
Vitamins and polyunsaturated fatty acids are a source of nutrition and medicines for humans. It has been reported that under certain conditions up to 85% of the dry weight of microalgae is lipids, and 30.229% of the total oil and fat content isγ-linolenic acid.
Pharmaceutical and biologically active compounds have already received considerable attention from researchers in the areas of pharmacy, antibiotics and biologically active compounds. Both cell extracts and growth media extracts of many unicellular algae(e.g. Chlorella vulgaris, Chlamydomonas pyrenoides) in vitro are effective against both Gram-positive and Gram-negative bacteria. Studies in this area began at the Roche Research Institute of Marine Pharmacology. A wide range of in vitro active anti-fungal activities have also been reported from extracts of green algae, diatoms and dinoflagellates.
Similarly, many microalgae have been screened to date and most of them contain and/or excrete pharmacologically active compounds. For example, the dinoflagellates Gymnodinium sp. and Gonyaulax sp. produce alkylguanidine compounds that affect the central nervous system, and extracts from Dunaliella tertiolecta and Rivularia firma show a range of pharmaceutical activities. In R. firma the activity is due to brominated bi-indoles.
The red unicellular alga Porphyridium cruentum and Gracilaria lichnoides have been found to produce lipid arachidonic acid, which is conventionally obtained from animal tissue such as the adrenal gland and liver. It is both an essential component of the humans diet and the precursor of a number of C20 compounds like prostaglandins, prostacyclins and thromboxanes. A kind of immobilized microsome prostaglandin is synthesized from alga-derived arachidonid acid. Optimal growing conditions (e.g. 320C, 8000lux) give a maximum arachidonic acid yield of (0.46mg l-1 h-1) in actively growing cultures. It is also produced in high concentration by the freshwater chryophytes Ochromonas danica, O. malbamensis and Poteriochromanas stipil. Microalgae such as Ochromonas sp., Prymnesium parvum Alexandrium catenella, Dinophysis aenta, and Gymnodinium breve and a number of blue-green algae produce toxins, but they have potential pharmaceutical application. Some blue-green algae, especially Lyngbya spiralis, have also shown to have anti-parasitic activity against Trichomonas sp.
Microorganisms in the ocean that are a resource for complex chemicals are an important locus of growth for our national economy
Sigma Co. of America produces more than ten thousand kinds of complex chemicals, most of which are from marine microorganisms. Over 98 % of such chemicals our country needs are imported from abroad. China should develop this chemicals industry. Its value could exceed that of all agriculture. In the US, the value of vitamins produced for human consumption is over 1.1 billion dollars. The price of prostaglandin is $8,600 /g, thromboxane $54,000 /g, EPA $25,000 /g and DHA $1,300 /g.
As of now, microbiology has already developed into a large number of subdisciplines, for instance, medical microbiology and immunology, clinical microbiology and virology, genetics and superfine structure, and molecular biology of industrial microorganisms.
There is a shortage of qualified scientists and technicians in all disciplines of microscopic organisms in our country
There are still empty fields like the biology of Archaea, Nanoplankton etc. Many people in charge of treating eutrophication of lakes and seas do not know what algae or the inception of productivity are. Therefore, Prof. Liu suggests that China should strengthen the development of the field of microbiology and energetically train qualified scientists and technicians to serve the national economy.