Introduction

Recently there has been a considerable increase in interest in developing genetically modified microorganisms (GMMs) for a range of different purposes in the environment such as bioremediation, mineral leaching, improvement of soil nutrient status and biological control. Numerous experiments, virtually all with bacteria, have been carried out using genetic manipulation to increase or decrease expression of genes associated with these processes or to transfer or delete them (see Crawford et al., 1993; Stotzky et al., 1993; Lindow, Panopoulos & MacFarland, 1989). However, before commercial development of these functional GMMs can occur, the environmental risks associated with the release into the environment of GMMs lacking deliberate functional manipulation must be addressed. Consequently, for the purpose of estimating the risks of such GMM releases, a series of step-wise assessment procedures has been developed. This approach was recommended by the Organisation for Economic Co-operation and Development (OECD, 1992) and has been adopted in regulatory frameworks in most countries. These start with laboratory and glasshouse studies under contained conditions and, depending on the results, are followed by field releases and post-release monitoring procedures.

Terminology associated with risk assessment is not strictly defined (see Teng & Yang, 1993), but essentially the key initial process in the risk assessment procedure is to identify any potential hazards associated with the use of a GMM. These include pathogenicity, phenotypic and genetic stability of the parental strain, potential for survival, establishment and dissemination, potential for gene transfer and, finally, potential to affect or cause an impact on other organisms or ecological processes.