In a broad sense, biotechnology is concerned with the manipulation of organisms to develop and manufacture useful products. The term “biotechnology” was first used in 1917 by a Hungarian engineer, Karl Ereky, to describe an integrated process for the large-scale production of pigs by using sugar beets as the source of food. According to Ereky, biotechnology was “all lines of work by which products are produced from raw materials with the aid of living things.” This fairly precise definition was more or less ignored. For a number of years, biotechnology was used to describe two very different engineering disciplines. On one hand, it referred to industrial fermentation. On the other, it was used for the study of efficiency in the workplace—what is now called ergonomics. This ambiguity ended in 1961 when the Swedish microbiologist Carl Göran Hedén recommended that the title of a scientific journal dedicated to publishing research in the fields of applied microbiology and industrial fermentation be changed from the Journal of Microbiological and Biochemical Engineering and Technology to Biotechnology and Bioengineering. From that time on, biotechnology has been defined as the application of scientific and engineering principles to the processing of material by biological agents to provide goods and services. It is grounded on expertise in microbiology, genetics, biochemistry, immunology, cell biology, and chemical engineering.
Commodity production by naturally occurring microbial strains on a large scale is often considerably less than optimal. Initial efforts to enhance product yields focused on creating variants (mutants) using chemical mutagens or radiation to induce changes in the genetic constitution of existing strains. However, the level of improvement that could be achieved in this way was usually limited biologically. If a mutated strain, for example, synthesized too much of a compound, other metabolic functions often were impaired, thereby causing the strain’s growth during large-scale fermentation to be less than desired. Despite this constraint, the traditional “induced mutagenesis and selection” strategies of strain improvement were extremely successful for a number of processes, such as the production of antibiotics.
The traditional genetic improvement regimens were tedious, time-consuming, and costly because of the large numbers of microbial cells that had to be screened and tested. Moreover, the best result that could be expected with this approach was the improvement of an existing inherited property of a microorganism rather than the expansion of its genetic capabilities. Despite these limitations, by the late 1970s effective processes for the mass production of a wide range of commercial products had been perfected.
Today we have acquired sufficient knowledge of the biochemistry, genetics, and molecular biology of microbes and other organisms to accelerate the development of useful and improved biological products and processes and to create new products that would not otherwise occur. Distinct from traditional biotechnology, the modern methods require knowledge of and manipulation of genes, the functional units of inheritance, and the discipline that is concerned with the manipulation of genes for the purpose of producing useful goods and services using living organisms is known as molecular biotechnology. The pivotal developments that enabled this technology were the establishment of techniques to isolate genes and to transfer them from one organism to another. This technology is known as recombinant DNA technology, and it began as a lunchtime conversation between two scientists working in different fields who met at a scientific conference in 1972. In his laboratory at Stanford University in California, Stanley Cohen had been developing methods to transfer plasmids, small circular DNA molecules, into bacterial cells. Meanwhile, Herbert Boyer at the University of California at San Francisco was working with enzymes that cut DNA at specific nucleotide sequences. Over lunch at a scientific meeting in Hawaii, they reasoned that Boyer’s enzyme could be used to splice a specific segment of DNA into a plasmid and then the recombinant plasmid could be introduced into a host bacterium using Cohen’s method.
Recombinant DNA Technology
It was clear to Cohen and Boyer, and others, that recombinant DNA technology had far-reaching possibilities. As Cohen noted at the time, “It may be possible to introduce in E. coli, genes specifying metabolic or synthetic functions such as photosynthesis or antibiotic production indigenous to other biological classes.” The first commercial product produced using recombinant DNA technology was human insulin, which is used in the treatment of diabetes. The DNA sequence that encodes human insulin was synthesized, a remarkable feat in itself at the time, and was inserted into a plasmid that could be maintained in a nonpathogenic strain of the bacterium E. coli. The bacterial host cells acted as biological factories for the production of the two peptide chains of human insulin that, after combining, could be purified and used to treat diabetics who were allergic to the commercially available porcine (pig) insulin. Today, this type of genetic engineering is commonplace.
milestone Construction of Biologically Functional Bacterial Plasmids In Vitro
Cohen SN, Chang ACY, Boyer HW, Helling RB. 1973.
Proc. Natl. Acad. Sci. USA 70:3240–3244.
The landmark study of Cohen et al. established the foundation for recombinant DNA technology by showing how genetic information from different sources could be joined to create a novel, replicable genetic structure. In this instance, the new genetic entities were derived from bacterial autonomously replicating extrachromosomal DNA structures called plasmids. In a previous study, Cohen and Chang (Proc. Natl. Acad. Sci. USA. 70:1293–1297, 1973) produced a small plasmid from a large naturally occurring plasmid by shearing the larger plasmid into smaller random pieces and introducing the mixture of pieces into a host cell, the bacterium E. coli. By chance, one of the fragments that was about 1⁄10 the size of the original plasmid was perpetuated as a functional plasmid. To overcome the randomness of this approach and to make the genetic manipulation of plasmids more manageable, Cohen and his coworkers decided to use an enzyme (restriction endonuclease) that cuts a DNA molecule at a specific site and produces a short extension at each end. The extensions of the cut ends of a restriction endonuclease-treated DNA molecule can combine with the extensions of another DNA molecule that has been cleaved with the same restriction endonuclease. Consequently, when DNA molecules from different sources are treated with the same restriction endonuclease and mixed together, new DNA combinations that never existed before can be formed. In this way, Cohen et al. not only introduced a gene from one plasmid into another plasmid but also demonstrated that the introduced gene was biologically active. To their credit, these authors fully appreciated that their strategy was “potentially useful for insertion of specific sequences from prokaryotic or eukaryotic chromosomes or extrachromosomal DNA into independently replicating bacterial plasmids.” In other words, any gene from any organism could theoretically be cloned into a plasmid which, after introduction into a host cell, would be maintained indefinitely and, perhaps, produce the protein encoded by the cloned gene. By demonstrating the feasibility of gene cloning, Cohen et al. provided the experimental basis for recombinant DNA technology and established that plasmids could act as vehicles (vectors) for maintaining cloned genes. This motivated others to pursue research in this area that rapidly led to the development of more sophisticated vectors and gene cloning strategies. It also engendered concerns about the safety and ethics of this kind of research that, in turn,