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Managing Global Genetic Resources: Agricultural Crop Issues and Policies 10 The Genetic Resources of Microorganisms Microorganisms generally receive scant or no attention in overall reviews of biological diversity and global genetic resources, perhaps because they are often studied by different methodologies and scientists based in laboratories rather than herbaria, museums, botanic gardens, or germplasm banks (Cronk et al., 1988; Office of Technology Assessment, 1987a; Plucknett et al., 1987; Wilson and Peter, 1988; Wolf, 1987). This is disproportionate to the key roles microorganisms play in the biosphere and is despite the extent to which they are already exploited commercially. Similarly, the genetic resources conservation movement has tended to underemphasize microorganisms, perhaps partly because of the common misconception that these are ubiquitous and so do not merit consideration in a conservation context. In ecosystems, microorganisms are important as symbionts (endophytes, mycorrhizae, and in insect guts), in nitrogen fixation (rhizobia, cyanobacteria, cyanobacteria-containing lichens), in the biodegradation of dead animal and plant material, and in controlling the size of populations of plants and insects through natural biocontrol. Microorganisms are not readily circumscribed. They include algae, bacteria (including cyanobacteria), fungi (including yeasts), certain protistan groups, tissue cultures, and viruses. Tissue cultures and animal and plant cell lines are not discussed here. This chapter assesses the extent of the maintained gene pool of microorganisms and focuses on the problems of preserving genetic stability in the long term and constraints to the development and
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies enhancement of microorganisms. The actions needed to safeguard this massive resource so that future generations can investigate its utility are also considered. ORGANIZATION OF MICROBIAL CULTURE COLLECTIONS The World Federation of Culture Collections (WFCC) is the key international coordinating body on the culture collections of microorganisms. This organization, established in 1970, is recognized by both the International Union of Biological Sciences and the International Union of Microbiological Societies and promotes liaison between individuals and organizations responsible for the maintenance and development of culture collections (Kirsop and DaSilva, 1988). A series of handbooks describing the resources available to culture collections has been initiated by WFCC; volumes concerned with filamentous fungi (Hawksworth and Kirsop, 1988) and yeasts (Kirsop and Kurtzman, 1988) have already been issued and others covering bacteria and animal cell lines are in preparation. The World Data Center for Microorganisms (WDC), now the responsibility of WFCC (Komagata, 1987), produced the first World Directory of Collections of Cultures of Microorganisms in 1972; the third edition of this directory (Staines et al., 1986) includes information on the names of organisms in 327 culture collections distributed throughout 56 countries. This information is complemented by the Microbial Strain Data Network (MSDN), sponsored by the Committee on Data for Science and Technology, WFCC, and the International Union of Microbiological Societies (Kirsop, 1988a). The MSDN was established in 1985 to provide on-line information on the data elements coded for strains by individual collections using a controlled vocabulary (Rogosa et al., 1986); it is accessed primarily by electronic mail. The United Nations Educational, Scientific, and Cultural Organization started to identify a series of microbial resources centers (MIRCENs) in 1974; (DaSilva et al., 1977; Kirsop and DaSilva, 1988; Zedan and Olembo, 1988). Sixteen MIRCENs are currently recognized worldwide and are expected to provide the infrastructure for an international network geared to the management, distribution, and utilization of the world's microbial gene pool. The European Culture Collections Organization, founded in 1982, has provided synopses of the resources available in Europe and arranges annual conferences. The Commission of the European Community commenced an ambitious program to establish a Microbial Information Network Europe (MINE) in 1985. Culture collections in Belgium, France, Greece, Germany, Italy, The Netherlands, Portugal,
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies Spain, and the United Kingdom enter data in a common format (Gams et al., 1988) through national centers to produce an integrated machine-readable catalog. In the United Kingdom, more extensive strain data, including biochemical and physiologic characteristics, have been compiled into the on-line Microbial Information Service (MiCIS); MiCIS and MINE are expected to become fully integrated. The objectives and key features of these systems have been compared by Allsopp et al. (1989). For the Scandinavian countries, the Nordic Register of Culture Collections was initiated in 1984, but this is not yet generally accessible. Nationally, culture collection liaison is, in some cases, coordinated by Federations of Culture Collections, as in Brazil, Japan, the United Kingdom, and the United States. These activities have been reviewed by Krichevsky et al. (1988). Only in the case of Brazil, however, has a single integrated national catalog been produced (Canhos et al., 1986). Individual culture collections can be divided into four main, but not mutually exclusive, categories. Service collections, which have as their primary objective the supply of authenticated cultures to all who request them. These are generally listed in publicly available catalogs; such collections are invariably directly or indirectly supported by government funds and supply cultures at less than full economic cost. In-house collections, which are established to meet the requirements of particular organizations, institutions, or individual companies. Collections of this type can be very substantial, but catalogs are not generally available and cultures are supplied on a discretionary basis. Research collections, which are built up by individual scientists or teams as a part of their research programs. Such collections are often unique resources, because they include novel and unusual strains in restricted groups, but long-term storage facilities are rarely adequate and resources permit cultures to be made available only to close colleagues. Research collections are often endangered or lost when individual scientists change positions, retire, or pursue different lines of research. Laboratory suppliers, which make available limited numbers of organisms, generally single strains of species, which are commonly used in teaching or research. Prices are generally below those that service collections are obliged to levy. The funding arrangements for culture collections vary markedly, but apart from some service collections sponsored by national governments or international coalitions of collections, these are rarely
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies adequate or sufficiently long-term to enable collections to optimize their value as a resource to the scientific community. Further information on particular collections and their services has been compiled by Hawksworth (1985), Hawksworth and Kirsop (1988), Kirsop and Kurtzman (1988), Malik and Claus (1987), and Staines et al. (1986). MICROBIAL RESOURCES IN CULTURE COLLECTIONS The only overview of the microbial resource maintained in culture collections worldwide is that found in the World Directory (Staines et al., 1986). Although this compilation cannot be considered comprehensive, particularly with regard to in-house and research collections, it includes all major service culture collections and does provide a reasonable approximation to the numbers of species of microorganisms available publicly. Because this catalog accepts whatever name is used for a particular organism by each collection (but cross-references synonyms), an allowance must also be made for synonymy in interpreting this compilation. Table 10-1, which was constructed to allow for this factor, indicates that about 18,500 species of microorganisms are currently available from culture collections. Species numbers alone do not, however, provide an adequate representation of the gene pool, in view of the considerable range of genomic variation known to occur even within single species. The number of microorganisms in which the genetic diversity has been analyzed in depth and experimentally is small. In those cases in which this has been accomplished, the numbers of genotypes distinguished can be substantial. For example, in the alga Chlamydomonas reinhardtii, 159 mutant lines are known (Harris, 1984; Harris et al., 1987); in the filamentous fungus Neurospora crassa, this figure is about 3,000 (Fungal Genetics Stock Center, 1988); in the yeast Saccharomyces cerevisiae, about 850 genetic strains are maintained at the Yeast Genetic Stock Center (Kirsop, 1988b); numerous special forms and races of plant pathogenic fungal species are kept at the collection of fungal pathotypes of the Institut voor Platenziektenkundig Ondersoek in Wageningen, The Netherlands; 6,000 strains of Escherichia coli with various genetic markers are maintained at the E. coli Genetic Stock Center (Bachmann, 1988), and some 1,500 serological types of Salmonella are maintained at the World Health Organization's International Salmonella Center (Staines et al., 1986). Nitrogen-fixing bacteria of the genus Rhizobium have been the focus of many collections; 73 collections in 38 countries have significant strains of the six species of this genus from about 220 different host legumes (McGowan and Skerman, 1986). Furthermore, many filamentous fungi (for example,
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies TABLE 10-1 Numbers of Species of Microorganisms Maintained in Culture Collections Compared with the Numbers Described and Probable World Species Totals Proportion of Species Maintained, in Percent Group Species in Culture Collectionsa Described Species Estimate of Total World Species Described World Estimate Algae 1,600 40,000c 60,000 4 2.5 Bacteria (including cyanobacteria) 2,200b 3,000 30,000 73 7 Fungi (including lichen-forming fungi) and yeasts 11,500 64,200d 800,000g 18 1.5 Viruses (including plasmids and phages) 2,900 5,000e 130,000 58 2 Protoctists (including protozoa, but excluding algae and "fungalprotoctists) 300 30,800f 100,000 1 0.3 Total 18,500 143,000 1,120,000 13 2 a Staines et al. (1986) rounded figures allowing for 25 percent synonymy in fungi and 10 percent in bacteria and algae. b Totals for species with valid names are given here. c P C. Silva (in Hawksworth and Greuter, 1989). d Hawksworth et al. (1983). e 700 Plant viruses (Martyn, 1968, 1971), 1,300 from insects (Martignoni and Iwai, 1981); those from other hosts are estimated. f Wilson and Peter (1988). g In a more recent study, Hawksworth (1991) conservatively estimates the total number of fungi species in the world as 1.5 million.
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies Coprinus and Schizophyllum species) have different, or in some cases multiple, mating type alleles, meaning that additional strains require preservation. Most collections do not specialize to the extent of individual genera or species, but to varying degrees, they concentrate on particular systematic or biological groups. Such specialization is usually in response to the requirements of the funding bodies of the collections or the particular research interests of the staff or institutions where they are located. Most also have strains predominantly isolated from the geographical area in which they are located. In view of these factors and bearing in mind the extent of infraspecific genetic variability that may well occur in many species, it is prudent to consider the existing culture collections as being essentially complementary rather than duplicatory. Even when strains derived from the same original isolation are retained in more than a single collection, they cannot be assumed to be genetically identical. This phenomenon results from the often inherent genotypic variability, so different genotypes may be deposited in different collections; inadvertent selection during maintenance for survival under the different preservation methods used; or contamination with other strains (Bridge and May, 1988; Bridge et al., 1986; Lawrence, 1982). The present efforts have developed on an ad hoc basis over the past 80 years, and at present, they do not appear to be capable of adequately conserving this vital world resource. Informal and often unwritten agreements to specialize in different areas exist between collections, as their curators are generally alert to the need to maximize their combined efforts to adequately preserve the microbial gene pool. Although the WFCC, through the WDC and MSDN, compiles data on the contents and coverage of collections, it has no executive authority over collections and lacks the resources needed to encourage and enable particular collections to expand to establish new collections where gaps in the world's coverage are identified. CONSERVING MICROBIAL DIVERSITY To make a realistic assessment of the efficacy of the current system of culture collections in conserving microbial diversity, it is useful to obtain estimates of the numbers of species of known or potential economic importance. Microorganisms, with the exception of some larger fungi, lichen-forming fungi, and larger algae, in general lack a history of inventory production on a regional basis equivalent to those of the floras and faunas covering, for example, vascular plants, bryophytes, birds, mammals, arthropods. In addition, when surveys
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies are carried out, only rarely is there any attempt to study systematically all the different habitats available even to a single group of microorganisms. This is an inevitable consequence of the labor intensiveness of sampling, culturing, and identifying massive numbers of microorganisms. Numbers and Richness of Microbial Species The numbers of species described and currently accepted in most groups of microorganisms worldwide can be estimated with some confidence from available catalogs of names (Table 10-1). However, about 120 new species of bacteria and 1,500 new species of fungi are described as being new to science each year, clearly demonstrating that knowledge of these groups is grossly inadequate. It is hazardous to extrapolate from such figures to the numbers that can reasonably be expected to occur in nature, particularly because the numbers of newly described species can be taken as an indication of the limited numbers of microbiologists actively engaged in systematic work rather than of the numbers of species to be found. An analysis of the information presented in Table 10-1 indicates that 1,120,000 is a reasonably conservative estimate of the world's microorganism species. With respect to culture collections, this indicates that, overall, only 2 percent of the species expected to be found are currently preserved in them. For all groups of microorganisms other than bacteria and viruses, only 1 to 18 percent of the described and currently accepted species are represented in culture collections, representing a mere 0.3 to 2.5 percent of the estimated number of species actually in the world. The higher proportions for bacteria, 73 and 7 percent, respectively, may be due at least in part to an underestimate of the known but now not validly published species and a consequently low value for the estimated figure worldwide. MAINTENANCE OF GENETIC STABILITY IN CULTURE Preservation methods of major service culture collections that aim to conserve genetic resources must be capable of maintaining genetic stability and viability in the long term. This is of major concern not only from the conservation standpoint but also to industry, agriculture, and medicine, for which particular biochemical, pathogenic, or other attributes need to be safeguarded. The problems are particularly acute with respect to plasmids and viruses, which must be preserved within the cells of the host organism. In the case of plasmids in bacteria and yeasts and of viruses in filamentous fungi, there is a
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies danger that the genomic material of the plasmid will be incorporated into that of the host (Chater, 1980). Strains cited in patents are deposited in specially recognized collections (Bousefield, 1988); such collections have a responsibility to maintain patent strains in an unaltered state for a minimum of 30 years (Crespi, 1985). Traditional Preservation Methods Traditional preservation methods involving regular subculturing of growth at low temperatures or maintenance under mineral oil are subject to inadvertent selection and contamination, especially when collections lack sufficient numbers of specialists to operate adequate quality control protocols. While growth is continuing, albeit at a much reduced rate, normal sexual processes involving changes in the genome can occur; these can include sexual and parasexual recombination, aneuploidy, and polyploidy. Freeze-Drying and Liquid Nitrogen Preservation In bacteria, yeasts, and filamentous fungi with discrete propagules, freeze-drying (lyophilization) in a cryoprotectant is currently the preferred long-term storage method; regular viability checks are still needed, however, as the long-term value of the method is not considered to be fully established. Freeze-drying gives very low survival rates for algae and protozoa and is not yet applicable in these groups. Liquid drying (drying without freezing) is used in some bacterial and yeast collections for strains that are difficult to maintain by freeze-drying (Banno and Sakane, 1979) and is adequate for at least 10 years. Bacteriologists sometimes also maintain strains as suspensions frozen onto glass beads and stored at -60 °C to -70 °C, but this cannot be recommended for resource centers when long-term viability must be assured. The ideal long-term preservation method for microorganisms is in the vapor of or immersed in liquid nitrogen at -150 °C to -196 °C when viability is expected to be indefinite. Rates of freezing and the cryoprotectant used can affect survival of the freezing process, but it is possible to tailor procedures to ensure optimal survival for particular groups (Morris et al., 1988). The development of protocols for cooling and thawing are also critical for many groups of algae and protozoa. At present even genetically important stocks of algae must be maintained by subculturing on agar plates, in liquid media, or in water. Light is essential for photosynthetic algae maintained by subculture techniques. The main disadvantage of the use of liquid nitrogen storage systems
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies is the cost of both refrigerated containers and the supply of liquid nitrogen; at least one major collection manufactures its own liquid nitrogen on site. In the case of microorganisms that cannot be grown on artificial media, such as many plant pathogenic fungi (for example, Puccinia rust) and plant viruses, they can sometimes be successfully maintained by placing the infected host tissue in liquid nitrogen. At present, the major service culture collections lack the substantial resources necessary to take advantage of the enormous potential for such on-host preservation. In both freeze-drying and liquid nitrogen storage techniques, as all metabolic processes are suspended, the possibility of genetic change taking place during extended periods of storage is precluded. However, instability can arise from differential survival of propagules during the freezing and thawing processes, and there is consequently some risk of inadvertent selection during the process. This is unlikely to be significant when a high percentage of the propagules survive the freezing process. Current research aims at improving protocols to maximize survival rates of individual propagules (Morris et al., 1988). A new generation of ultra-low-temperature mechanical refrigerators able to operate below -130 °C are becoming available and may provide an alternative to liquid nitrogen storage in the future. Various aspects of stability have been discussed by Kirsop (1980); for further information on the preservation methods for microorganisms see Gherna (1981), Kirsop (1988c), Kirsop and Snell (1984), Malik and Claus (1987), Smith (1988b), and Smith and Onions (1983). MAINTENANCE IN NATURAL HABITATS Although the conservation of habitats for other groups of organisms inevitably safeguards the environment for those microorganisms that are already present, the range of potential habitats to be safeguarded is immense and these do not always coincide with those environments that are important for other groups of organisms. Furthermore, because of the current state of knowledge of the world's microbial groups, habitats previously unexplored and considered unimportant repeatedly yield novel organisms (see above). The concepts of the classification of plant communities and centers of plant diversity that are proving of value in the conservation of vegetation types (International Union for the Conservation of Nature and Natural Resources, 1987) are difficult to translate into microbiology. Some of the problems encountered with respect to the fungi have been reviewed by Apinis (1972). In addition, while a scientist wishing to collect a particular flowering
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies plant, tree, bird, or mammal known to be in a conserved habitat should have a high expectancy of success, the isolation of micro organisms is both a time-consuming and an uncertain task. Interesting and novel strains are not uncommonly found at low frequencies. Furthermore, many of the larger fungi, rusts, smuts, and other host specific species are strongly seasonal in occurrence, may not be visible in every year, or may have fruiting bodies that mature and disappear within a few hours. The probability of a research worker being able to obtain another isolate of a strain from a particular habitat in situ is, consequently, often extremely low. It could also be both exorbitantly expensive, time-consuming, and cost-ineffective. In addition, because the ecological roles and extent of functional redundancy among microorganism populations are unknown, management schemes to preserve then in situ cannot, in most cases, be made with confidence. Once isolated in culture and found to be new or to have new properties, the only realistic option available to ensure that it continues to be available is in most cases ex situ conservation in a culture collection. Only in the case of perennial lichen-forming fungi is habitat conservation a realistic measure for the maintenance of microbial diversity (Seaward, 1982). Although the conservation of unmodified natural habitats should be supported by microbiologists, as they are sources of numerous novel organisms, in general, in situ conservation is not a viable option for the supply of already isolated and characterized microbial genetic material to researchers. POTENTIAL OF MICROBES IN THE AGRICULTURAL, BIOTECHNOLOGICAL, AND INDUSTRIAL SECTORS The current uses to which microorganisms are put in the agricultural (including food), biotechnological, and industrial sectors are manifold and difficult to summarize succinctly (Table 10-2). Worldwide, the positive economic value of microorganisms must be calculated in at least many tens of billions of U.S. dollars, bearing in mind their role in the pharmaceutical and fermentation-based industries. However, the economic potential of only a small percentage of the microorganisms already present in culture collections has been investigated. Exploitation of Metabolites An indication of the richness of microorganisms is by the number of secondary metabolites from these organisms that are exploited. By
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies 1974, 3,222 antibiotics were known from microorganisms (Berdy, 1974), about 60 percent of these being from actinomycete bacteria. The filamentous fungi are particularly promising from this standpoint: while ß-lactan antibiotics continue to be of major importance, significant new drugs are being obtained from fungi, including ones that act as immunosuppressants and those that lower cholesterol levels. Cyclosporin, first approved for use in 1983 and obtained from a fungus regarded for almost a century as unimportant, helps prevent the human body from rejecting organ transplants (Winter, 1985). Secondary metabolites have been reported from only about 2,000 species of fungi, or 3 percent of the known species, and most species have been represented by single strains studied when grown under a single set of conditions. Numerous biologically active metabolites remain to be isolated and characterized. When a desired property is located, production can be increased dramatically by strain improvement; Penicillium strains that produce over 25,000 units of penicillin per ml are now used, early Penicillium strains produced only 300 units per ml (Kristiansen and Bu'Lock, 1980). Genetic Engineering Genetic engineering methods increase the potential applications of the beneficial products that are discovered. Gene sequences producing desired enzymes or other compounds from one organism can be introduced via plasmids into the cells or, in some cases, the genomes of hosts, which can be cultured in bulk. Examples are the transfer of the insecticidal crystal protein gene from Bacillus thuringiensis into Escherichia coli (Qi and Yunliu, 1988); manufacture of human insulin, alpha interferon, and other products from similarly engineered E. coli strains (Primrose, 1986); transfer of enzymes from filamentous fungi to yeasts (van Arsdell et al., 1987); transfer of human tissue plasminogen activator genes into filamentous fungi (Upshall et al., 1987); and the expression of human immunodeficiency virus enzyme into years (Barr et al., 1987). The range of possibilities is immense, and the technology is rapidly advancing (Bennett and Lasure, 1985). Hybridization between protoplasts of different species of fungi and the subsequent production of recombinants has been effected and has opened an area with tremendous promise (Peberdy, 1987). Application of Microorganisms in Agriculture The range of applications of microorganisms in agriculture is already substantial and is rapidly developing into new areas. The Ti
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies TABLE 10-2 Applications of Microorganisms in the Agricultural, Biotechnological, and Industrial Sectors Uses Examples of Microorganisms Used Selected References Cheese production Bacteria (Lactobacillus, Streptococcus) and fungi (Penicillium) Marth (1982) Beers, wines, brandy, and distilled alcohols Fungi (Saccharomyces) Benda (1982), Brandt (1982), Helbert (1982) Biocontrol of grasshoppers Protozoa (Microsporidium moscema lacustris) R.J.L. Muller, International Institute of Parasitology, St. Albans, United Kingdom, personal communication, September 1989 Biomass conversions (waste biodegradation) Bacteria (Clostridium) and fungi (Sporotrichum, Trichoderma) Birch et al. (1976), Rolz (1984) Breads Fungi (Saccharomyces) Ponte and Reed (1982) Fermented foods Bacteria (Pediococcus) fungi (Monascus, Neurospora, Penicillium, Rhizopus, Saccharomyces) Steinkrause (1983), Wang and Hesseltine (1982) Food (direct usage) Fungi (Agaricus, Auricularia, Lentinus, Pleurotus, Tremella, Volvariella) Chang and Hayes (1978), Wu (1987) Organic acids (e.g., citric, oxalic) Bacteria (Bacillus), fungi (Aspergillus, Candida, Penicillium, Pichia) Meers and Milsom (1987) Vitamins ( e.g., riboflavin) Fungi (Aspergillus, Blakeslea, Nematospora) D.L. Hawksworth, International Mycological Institute, personal communication, January 1989) Enzymes (e.g., cellulases, lipases) Bacteria (Bacillus, Escherichia), fungi (Aspergillus, Auerobasidium, Candida, Rhizoctonia, Trichoderma) Böing (1982), Moo-Young et al. (1986)
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies Antibiotics Bacteria (Streptomyces), fungi (Acremonium, Penicillium) Blanch et al. (1985), Berdy (1974, Goodfellow et al. (1988) Amino acids (e.g., glutamic acid) Bacteria (Corynebacterium, Brevibacterium, Escherichia) Nakayama (1982) Fuel production (acetone-butanol, ethanol, biogas) Bacteria (Clostridium), fungi (Saccharomyces) Blanch et al. (1985), Moo-Young et al. (1986) Herbicides Fungi (Collectotrichum) Templeton et al. (1979) Nitrogen fixation Bacteria (Rhizobium) Pesticides Bacteria (Bacillus), fungi (Beauveria, Trichoderma, Verticillium), viruses (Baculoviridae) Aronson et al. (1986), Brady (1981), Entwistle (1983), Wood and Way (1988) Blood products (e.g., factor 8, interferon) Bacteria (engineered Escherichia coli) Primrose (1986) Pickling (lactic acid fermentation) Bacteria (Lactobacillus, Leuconostoc, Pediococcus) Vaughn (1982) Protein (single-cell) Algae (Chlorella, Scenedesmus, Spirulina, bacteria (Methylophilus, Pseudomonas), fungi (Candida, Chaetomium, Fusarium, Paecilomyces, Trichoderma) Birch et al. (1976), Kristiansen and Bu'Lock (1980), Olsen and Allermann (1987), Reed (1982) Sausages (fermented; e.g., salami) Bacteria (Lactobacillus, Micrococcus, Pediococcus) Haymon (1982) Mycorrhizae Fungi (Boletus, Rhizoctonia, Russula) Harley and Smith (1983) Vinegars Bacteria (Acetobacter) Ebner (1982) Waste detoxification Algae (Prototheca, Scenedgumm) Robinson et al. (1988) Yogurts (and other fermented dairy products) Bacteria (Lactobacillus, Leuconostoc, Streptococcus) Chandan (1982)
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies plasmid of Agrobacterium tumefaciens is important to biotechnology and plant breeding for use in introducing cloned genes into a variety of crop plants (Fillatti et al., 1987). The potential for introducing gene sequences from bacteria or fungi capable of producing natural insecticides into the genomes of crop plants is especially exciting. Following the recognition of the role of bacteria on plant surfaces in ice nucleation and, therefore, frost damage, new horizons for the control of this damage have opened (Lindlow, 1983); application of Pseudomonas syringae strains that lack a crucial protein favoring ice nucleation reduces frost damage. The application of microorganisms in the biocontrol of pests and weeds are becoming increasingly recognized. The bacterium Bacillus thuringiensis can control a wide range of insect pests, especially lepidopteran larvae (Aronson et al., 1986), as can strains of some fungi, particularly Metarrhizium species (Brady, 1981), and insect viruses (Entwistle, 1983). Work on the control of weeds by using fungal pathogens is arguably one of the fastest growing areas of biocontrol, with narrowly host specific Cercospora and Collectotrichum strains and rusts proving to be particularly efficacious (Wood and Way, 1988). There is also major potential for new applications in the conversion of agricultural, forestry, and other wastes to usable products such as cattle feed; in the detoxification of harmful compounds in situ by microorganisms (Sahasrabudhe and Modi, 1987); and in the control of environmental pollution (Hardman, 1987). Immobilized microalgal cells show potential for a wide range of applications, including the accumulation of phosphate ions from effluents and chlorinated hydrocarbons (Robinson et al., 1988). A new strain of Pseudomonas tolerant of toluene also promises to be of value in pollution control (Inoue and Horikoshi, 1989). In developing countries, major short- and medium-term benefits can be expected from improved inocula for mycorrhizae and nitrogen-fixing Rhizobium strains; these improve tolerance to environmental stress and reduce the need to apply artificial fertilizers, respectively (Mantell, 1989). In addition to new and developing fields described above, it must not be forgotten that living collections of microorganisms are also relevant to breeding programs, because authentic sources of pathogens are prerequisites for resistance testing in both plant and animal breeding programs. They are also essential for raising monoclonal and polyclonal antibodies and developing other diagnostic methods for the rapid identification of pathogens; the strains from a wide geographic or host spectrum essential to developing such systems are only likely to be supplied quickly through service culture collections.
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies RECOMMENDATIONS The microbial genetic resources base currently maintained in culture collections worldwide is scarcely representative of the global genetic resource. This situation is fully recognized by the WFCC; indeed, the Sixth International Congress of Culture Collections held at the University of Maryland in November 1988 passed a resolution calling for "appropriate financial and material support for research on the isolation, characterization, systematics, ecology and conservation of natural and genetically engineered organisms to enable the Collections to competently and professionally fulfill their research and service potentialities" (Canhos, 1989:501). The need to conserve genetic resources was stressed in 1972 at the United Nations Conference on the Environment (United Nations, 1973). Unfortunately, the participants did not appear to have appreciated the enormous diversity of microorganisms not preserved in culture collections. The recommendations mentioning microorganisms focused on the production of inventories of collections, although it was suggested that governments "cooperatively establish and properly fund a few large regional collections" (Unit Nations, 1973:15). This last proposal has not been taken up internationally to any significant extent, with notable exceptions being the MIRCEN-sponsored collections in developing countries (Kirsop and DaSilva, 1988). Frankel (1975a) considered the following actions to be necessary to conserve the world's genetic resources of crop plants: (1) linking existing institutions by agreements for the exchange of material and information; (2) the designation of base collections for particular crops or regions operating under agreements on technical standards; (3) the establishment of a cooperative network of data banks; (4) institution of a program of emergency collecting of threatened genetic resources; and (5) training in genetic resources work. All these actions are equally applicable to microorganisms, with only minor modifications and additions. International and national action is needed in several areas to adequately conserve the world's microbial gene pool. A much greater proportion of the microbial gene pool must be captured in world collections. The number of species in service culture collections worldwide needs to be increased substantially. Increased acquisitions of strains from previously unexplored habitats and regions will inevitably lead to the discovery of species not previously known in culture and species that have not been described previously. The priority must clearly
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies be species and strains already proved to be of value to humans The second priority should be those species that have already been described, that is, biotic material about which something is known. This would provide a cost-effective opportunity to build on what is already known without the need to attempt to repeat original isolations or characterizations. Further, retaining these is preferable to the costs and uncertainties of reisolation. To achieve these two objectives, a substantial increase in existing capacity would be required (Table 10-1). The system of base collections specializing in particular regions developed by the International Board on Plant Genetic Resources appears to be a model for developing a strategy for the world conservation of microorganisms. Secure, long-term international funding is needed for conserving, managing, and using the world's microbial diversity. Because service culture collections must necessarily take a long-term view of their role in conservation, it is imperative that they preserve as a wide a range of the world's microbial genetic resources as possible. Funding must be sufficient both to maintain a sufficient volume of strains and to enable long-term preservation methods and adequate quality control procedures to be implemented. If the model of world base resource collections is eventually adopted for microorganisms, international rather than national funding will be required. The figures given in this chapter demonstrate that the global genetic resource of microorganisms is not adequately conserved in existing culture collections. The extent to which increased resources should be devoted to isolating additional species and maintaining them must reflect their potential value. In the first instance, the priority in the case of service collections should be to make available known species and strains whose activities have been documented. Isolation, culture, preservation, and documentation methods are needed for conservation and to ensure the long-term viability and usefulness of microbial resources. Particular attention needs to be given to the preservation of obligate pathogenic and symbiotic microorganisms, together with infected hosts or their natural symbionts, especially since many of these microorganisms can be expected to have potential biocontrol and in enhanced productivity. Researchers often need to locate strains with particular combinations of physiological, biochemical, and other attributes. To do this,
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Managing Global Genetic Resources: Agricultural Crop Issues and Policies computerized data bases readily accessible over telephone lines or electronic mail networks are required; significant progress in this direction is being made through the MSDN and MINE/MiCIS initiatives (see above), but progress has been slow because of limited resources.
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Representative terms from entire chapter: