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Chapter 11 Future Perspectives in Microbiology Certain major turning points in history have resulted from scientific break- throughs, but the advances from the new knowledge have not been restricted to science. Rather they have also helped solve philosophical puzzles, changed economies, and often improved the quality of life. Science and technology are being called on today to help mankind alter a pattern of life that has been lavish in the use of finite natural resources and turn to one more dependent upon renewable substances. Two significant kinds of renewable resources are those that depend on photosynthesis and those that take advantage of the useful and beneficial activities or properties ~ . . OI mlCrOOrgaIllSmS. In previous chapters of this report, a few well-known examples were cited to illustrate the impact that microbiology has had on human welfare. But what about the future? In this brief chapter, mention will be made of addi- tional areas in microbiology that may—if certain developments occur-lead to great economic and social benefits as well as contributing to fundamental knowledge. Development of this potential need not be restricted to highly developed industrialized countries; in fact, some advances in microbiology may more easily come from less-developed regions of the world. New basic techniques are being discovered and old ones improved in biol- ogy, biochemistry and chemistry. Some of these techniques are precise and relatively easy to perform. Others are more complex and require expensive instruments and facilities not available to all scientists. Still others depend upon microbiological techniques such as animal and plant tissue culture re- search. Plant tissue culture, for example, may lead to improved varieties of plants by enabling scientists to select mutants (both in haploid and diploid lines) and to study protoplast fusion, regeneration of whole plants, and other plant functions. Much of our recent knowledge in genetics and molecular biology that is leading to so-called genetic engineering has been cradled in microbiology. There is little doubt that basic and applied research with microorganisms in these fields will continue to provide valuable information and technology of economic value. This knowledge can be used for improvements on com- 186
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FUTURE PERSPECTIVES IN MICROBIOLOGY 187 mercial fermentation processes, in agriculture, in the pharmaceutical industry for production of improved bacterial and viral vaccines, and possibly in mak- ing substances to correct metabolic defects in human beings. For example, bacteria were recently engineered to make insulin by transplanting into them the gene from rat cells that carries the instructions to synthesize insulin. Much research remains to determine whether such insulin will function in human diabetics, if the bacteria can be implanted in the human intestine, and if they will then continue to produce the hormone. In a similar manner, a strain of Escherichia cold has been used to produce in the laboratory the human hormone somatostatin, which is normally formed in the hypo- thalamus at the base of the brain. Research on plasmids formed by the bacterium Agrobacterium tume- faciens is giving us much basic information on how tumors are produced in plants. This knowledge may be helpful in other types of cancer research; other similar ways of using microorganisms for cancer study are in experi- mental stages. Certain bacteria (Halobacterium halobium) contain in their cell mem- branes a purple protein pigment closely related to the visual pigment of vertebrates. Indications are that the vertebrate purple protein constitutes an essential link in the signal chain of the visual process in animals and human beings. Speculation is that research on the bacterial purple pigment will help explain the mechanism of how animals see. Some microscopic marine green algae (Dunaliella species) grow in waters of high salt content (for example, the Red Sea and the Dead Sea), where they produce large quantities of glycerol. Possible commercial extraction of the glycerol from these algae is contemplated. Microorganisms are known to produce a wide variety of metabolic prod- ucts; in fact, over 5,000 metabolites have been identified and some 500 enzymes described. Most scientists believe these metabolites and enzymes represent only a fraction of the total existing in nature. It seems reasonable to assume that some of these substances may be useful and have economic value. In fact, interesting possibilities exist that some of these substances have pharmacological potential. For example, Japanese scientists have isolated from culture filtrates of actinomycetes (Streptomyces testaceus) a substance called pepstatin, possessing strong antipepsin activity. The substance is being used to analyze the role of pepsin in stomach or duodenal ulcers. Certain microorganisms produce antitumor compounds, which show promise for future production by fermentation and eventually for therapeutic use. A species in the bacterial genus Nocardia, for example, produces potent com- pounds called ansamitocins, which are active antitumor substances. Culture filtrates of a fungus (~Fusarium oxysporum) contain a compound identified as fusaric acid, which inhibits the enzyme dopamine-,B-hydroxylase. This enzyme appears to be related in some way to Parkinson's disease in
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188 MICROBIAL PROCESSES human beings. Also, oral administration of fusaric acid causes experimental animals and human beings to become sensitive to alcohol. Unpleasant side effects often result when persons eat mushrooms (Coprinus atramentarius) and drink alcoholic beverages. Scientists have recently discovered the basic anti-alcohol compound (coprin) in the mushroom, and it may become effec- tive in the treatment of alcohol addiction. Further study of these relation- ships may contribute to our knowledge of Parkinsonism and alcoholism, and in turn have profound social, medical, and economic significance. Similar examples can be cited of microbes producing substances that lower hypertension and destroy cholesterol in the blood, or serve as anti-inflamma- tory agents, neuromuscular blocking compounds, or other useful pharma- cological agents. Agriculture can also benefit from microbial research. One illustratio among many is the unique product produced by bacteria (Pseudomonas abikor~ensis, P. fianii) that inhibits the growth of the bacterium (Xan- thomonas citri) responsible for cankers on citrus-fruit trees and the fungus (Piricular~a oryzue) that causes blast in rice. The discovery that biologically active substances can be fixed artificially to insoluble polymers (such as membranes and particles), which act as supports or carriers, has greatly advanced certain areas of science and technology. Useful microbial enzymes that are rapidly inactivated by heat can be stabi- lized by attachment to inert polymeric supports, and in other cases these so-called "insolubilized microbial enzymes" can be used in nonaqueous envi- ronments. Whole bacterial cells can also be immobilized inside poly- acrylamide beads and used for a variety of purposes. The possibilities seem limitless for the use of certain microbial cells and their products. The transfer of microbial DNA to plant cells in nature appears to be of considerable importance in causing plant diseases and economic losses. This area of plant pathology and microbiology deserves more attention. For instance, crown gall in plants is initiated during the first few days of infection by the causative bacterium (Agrobacterium tumefaciens). But once the plant cells are transformed and have produced a gall, the living bacteria are no longer necessary to maintain the tumorous state. Tumor cells free of bacteria can be isolated from diseased plants and cultured in vitro by usual tissue- culture methods. Such cultured cells of crown gall proliferate as tumors when grafted onto suitable host plants, and in some cases even pass on the trans- formed characteristics to the healthy host cells. Study of these characteristics may be important to the understanding of mechanisms that control—or fail to control—orderly cell multiplication. New hope for discovering chemical substances to cure virus diseases has arisen with the successful use of adenine arabinoside to treat herpes enceph- alitis, a virus disease that destroys brain cells. Similar viruses cause fever blisters, genital herpes, and other diseases. This advance may be comparable to the discovery of penicillin.
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FUTURE PERSPECTIVES IN MICROBIOLOGY 189 The possibility of using the unicellular alga Cosmarium turpinni as a protein supplement for animal feeds holds promise. When this alga is culti- vated in the laboratory in the presence of cellulysin (from Trichoderma reesei) it forms only protoplasts (cells without rigid cell walls) either in light or in the dark. This obviates having to break cell walls to release cellular proteins, which is one of the problems associated with the use of single-cell proteins for livestock and poultry feeds. Interest in geomicrobiology has been growing in recent years, with the development of new insights into the role of microbes in a number of geo- logical processes. Microbes are now recognized as important geologic agents, playing a role in such geologic processes as mineral formation, mineral degra- dation, sedimentation, weathering, and geochemical cycling. From a human standpoint, these processes may either be beneficial or harmful, depending on the context. Beneficial effects include microbial extraction by solubilization (leaching) of commercially useful substances. This enables metals like cobalt, copper, lead, zinc or uranium (see Chapter 6) to be separated from low-grade ores from which they cannot be economically extracted by more conventional methods of milling and flotation. Beneficial effects may also include the microbial genesis of sulfur from sulfate or of methane from organic residues in natural environments, immobilization or volatilization of polluting toxic elements such as arsenic or mercury, the microbial desulfurization of coal, the microbial removal of methane from coal mines, and the use of aliphatic hydrocarbon-utilizing bacteria in prospecting for petroleum deposits. Harmful effects may be the microbial genesis of acid mine-drainage from microbial pyrite oxidation in bituminous coal seams, occurring after exposure to air and moisture during mining; the release of toxic substances such as antimony or arsenic from naturally occurring minerals into the environment; or the microbial weathering of building stone such as limestone, leading to defacement or structural weakness. Discoveries of previously unknown microbial interactions with inorganics, like the deposition of manganese in nodules and crusts on the ocean floor, are continuing and will provide further insights into geological processes and are likely to yield many new practical applications of microbes for economic benefit. For instance, two useful microbial processes are being tested for obtaining petroleum products from oil shale and tar sands. Carbonates in shale decrease permeability and hinder extraction of the oil. By applying certain bacteria that produce acids from shale components, the carbonates are dissolved in the shale matrix, increasing porosity and facilitating the removal of oil products. Many difficulties exist in the extraction of oil from the tar sands. A novel approach for obtaining hydrocarbons from such sands has been described whereby microbes adsorb and emulsify the oil, thus aiding in conventional processing methods.
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190 MICROBIAL PROCESSES The search for life on other planets has been largely unsuccessful, but it has provided new techniques for the identification of microbes and their products using automated and miniature apparatus. This kind of apparatus is finding important application in other fields of biology. For example, so- called pyrolysis-spectrometry techniques can distinguish between healthy and diseased or abnormal tissues in the body. High hopes exist for using these techniques to reduce the time required to identify genetic defects in fetal cells obtained by amniocentesis. The search for microbes on other planets may thus be responsible for important spin-offs that may have considerable significance in the future. From these brief descriptions of microbial processes, it is apparent that the science of microbiology has reached a point where it can make real contribu- tions to improving the welfare of mankind. The main question now is whether ingenious and well-informed microbiologists and bioengineers have the vision—and the ability—to convince the public that the beneficial activ- ities of the microbial world can be exploited for human good. References and Suggested Reading Anonymous.1977.Proteinsfromsyntheticgenes.lVature270:202. Borowitzka, L. J., et al. 1977. The salt relations of Dunaliella. Further observations on glycerol production and its regulation. Archiv fuer Mikrobiologie 1113 :131-138. Brady, R. O., et al. 1974. Replacement therapy for inherited enzyme deficiency. Use of purified glucocerebrocidase in Gaucher's disease. New England Journal of Medicine 291:989. Brierley, C. L. 1978. Bacterial leaching. CRC Critical Reviews in Microbiology 6: 207-262. Da Silva, E. J., Olembo, R., and Burgers, A. 1978. Integrated microbial technology for developing countries: springboard for economic progress. Impact of Science on Soci- ety 28:159-182. Dimmung, W. 1977. Feedstocks for large-scale fermentation processes. In Microbial en- ergy conversion, H. G. Schlegel and B. Barnea, eds. Oxford: Pergamon Press. Heden, C.-G. 1977. Enzyme engineering and the anatomy of equilibrium technology. Quarterly Review of Biophysics 10:1 13-135. Henderson, R. 1978. The purple membrane of halobacteria. In Relations between struc- ture and function in the prokaryotic cell: 28th Symposium of the Society for Gen- eral Microbiology, University of Southhampton, April 1978, R. Y. Stanier, H. J. Rogers, and J. B. Ward, eds., pp. 225-231. Cambridge-New York: Cambridge Univer- sity Press. Litchfield, J. M. 1977. Single-cell proteins. Food Technology 31:5:175-179. Prave, P. 1977. Utilization of microbes-modern developments in bacteriological tech- nology. Angewandte Chemie (En". ea.) 16: 205-213. Snyder, H. E. 1970. Microbial sources of protein. Advances in Food Research 1 8:85-140. Stanton, W. R., and Da Silva, E. J., eds. 1978. GIAM V. Global impacts of applied microbiology. State of the art: GIAM and its relevance to developing countries. pp. 323. Kuala Lumpur: University of Malaysia Press. Tannenbaum, S., and Wang, D., eds. 1975. Single-cell protein II. Cambridge: MIT Press. Viking Mission to Mars. Science 193(4255):759-815. Waslein, C. I., et al. 1969. Human intolerance to bacteria as food. Mature 211 :84-85.
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