Manipulation of Bacteria by Genetic Engineering
Genetic manipulation by the deliberate introduction of defined genes into a specified organism is a very powerful technique which is relatively new and certainly in constant development, sometimes at phenomenal rates of progress. The techniques have produced some exciting hybrids in all areas of research, both microscopic; bacteria and fungi, usually described as recombinants, and macro-scopic; principally higher plants and animals, commonly described as transgenics. The latter term refers to the principle of deliberate transfer of a gene from one organism to another in which it is not normally resident. This earns the incom-ing gene the title of ‘foreign’. Some examples of these which are relevant to environmental biotechnology will be discussed later.
Some of the developments are of great potential interest and represent some exciting and innovative work. However, it must be said that, in practice, a very tiny proportion of all endeavour in the name of environmental biotechnology has, or is likely to have in the future, a direct reliance for its effectiveness on the type of recombinants and transgenics currently being developed. This is not because of the limits of genetic engineering, which in principle are almost boundless, given sufficient resources, but because of cost. It is a principal factor as the technology and research to produce transgenic organisms attract an inherently high price. While such a situation may be sustainable by pharmaceutical compa-nies and perhaps to a lesser extent, agribiotechnology companies possibly able to command a high return on sales of the product, it is rarely sustainable in appli-cations of environmental technology. Few commercial organisations are excited at the prospect of spending a large proportion of their income on waste disposal for example, and will normally only do so when absolutely necessary.
There are other factors which affect the suitability of transgenic organisms in this science due to current requirements for containment. In addition, the way in which such a recombinant is utilised may cause problems of its own. For example, if the recombinant is a micro-organism structured to improve the rate of degradation of a pollutant, its performance may be exemplary in laboratory conditions but when it is applied in bio-augmentation it is in competition with indigenous species which could outgrow the recombinant. The novel bacterium may also lose its carefully engineered new capability through normal transfer of genes given the high level of promiscuity between bacteria. A highly controlled and contained environment such as a bioreactor may circumvent some of these objections but it is not always practical to move the contamination to the solution rather than the solution to the contamination. Again this involves expense and practical considerations, not least of which are safety concerns associated with the transport of contaminated material.
In reality, there is rarely any need to use recombinants or transgenics and it is far more likely that the required metabolic capability will be provided by indigenous organisms, or ones which have been trained for the task. There are, however, some exotic and ingenious applications, and by way of illustration, some examples are given here. The aim is to provide an overview of some of the more frequently used technologies together with specific examples. There are very many excellent textbooks and specialised publications which should be consulted should a more detailed and working knowledge be required. However, an overview of the principles of genetic engineering are given here for the benefit of those unfamiliar with the technology.