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be adequate to assess the risk of gene transfer. Gene transfer of synthetic plants depends on the likelihood of
plant pollination, but also the release of high-copy plasmids from dead cells might result in gene transfer.
Interactions between plants with synthetic modifications and natural organisms have to be considered as well.
Such modifications may enable synthetic cells to adhere with natural cells or invade cell membranes.
Experiments need to be carried out in order to measure any synergistic or toxic effect on cells caused by the
synthetic plant (Moe-Behrens et al. 2013).
Currently, it is highly unclear how all risks that may occur with synthetic higher plants can be fully assessed.
This applies in particular for organisms which are based potentially on a different nucleic acid or on an
enlarged genetic alphabet. In this context it has to be noted that organisms based on an enlarged genetic
alphabet might avoid natural predators at all, possibly enabling unrestricted spread. Moreover, the use of an
extended genetic code is mentioned in scientific literature, but only in connection with bacteria and not with
higher plants. So it is speculated that the use of an extended genetic code and a corresponding novel
polymerase could lead to a synthetic
Escherichia coli organism. However, it is extremely unlikely that anything
like that or even more that a synthetic higher plant will soon occur (Schmidt 2010a).
5.4
Assessment of the practical consequences and risks of a release into the
environment of plants created by synthetic genomics
From the data available, it is extremely unlikely that release experiments of synthetic higher plants in the strict
sense will be performed in the near and mid future. What is more realistic are synthetic biology approaches
implemented for the development of photosynthetic microorganisms, cyanobacteria and microalgae
(unicellular algae). Different approaches for redesign of the photosynthetic apparatus of microalgae or novel
pathway for the production of compounds with novel chemical properties were reported (Zurbriggen et al.
2012).
Microalgae modified by genetic engineering are currently used for different industrial processes, of which the
most prominent is the production of biofuels (Wageningen UR 2014). The most important risk assessment
strategies for these release scenarios have been described which provide fundamental aspects that are
essential to be mentioned also with respect to microalgae produced by new technologies including synthetic
biology.
Microalgae can be cultivated in different aqueous systems, from open air ponds to closed bioreactors with
closely controlled environments. Potential hazards may be identified in connection with the amplification of
microbial populations, microalgae (including synthetic organisms), toxins, and enzymes in such cultivation
systems that may be potentially hazardous to the environment and individuals. Each process could produce
potentially pathogenic, toxic, infective, or allergenic compounds. Any impacts of a release scenario, therefore,
can be risk assessed only by the complete understanding of the process employed and the specific algal
organism used. Specifications of the synthetic organisms and their behaviour under different conditions need
to be fully understood and characterised.
Therefore, the most important points in relation to the risk assessment of the production of industrial
compounds including biofuels by synthetic microalgae are (modified from EFSA (2011); Wozniak et al. (2012)):
submission of all available data on the microorganism(s) (e.g. the synthetic biology approach) and the
planned
activities,
a priori evaluation of the release into the environment,
information and discussion concerning actual or potential effects on health
or the environment of the
microalgae along with their phenotypic and ecological characteristics,
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utilisation of experimental data proving the absence of pathogenicity (e.g. toxicity studies) taking
account of:
the presence and levels of synthetic material or other new constituents (synthetic DNA/proteins,
unnatural
molecules, etc.)
the differences between the synthetic organism and natural systems regarding e.g. gene regulation,
metabolic functions, chemistry, cellular components, responses
to different environments
the impact of other changes in anatomical, nutritional and physiological characteristics
due to the
synthetic design process
information about the proposed field testing activity including the objectives and significance of the
activity with a rationale for the release in the environment,
the numbers and frequency of microorganisms released
by the proposed application,
full characterisation of the location including the geographical, physical, chemical,
and biological
features, and proximity to human habitation or activity, and
description of the proposed confinement procedures, potential mitigation and emergency procedures,
and the procedures for routine termination of the activity.
5.5
Biosafety considerations on BioBricks™ used for Synthetic Biology
The backbone of biosafety assessment is the classification of host (micro-) organisms into four risk groups as
set out in Table 5 (WHO 2004).
Risk
Classification
Definition
Explanation
Risk Group 1
no
or
low
individual
and
community risk
A microorganism that is unlikely to cause human or animal disease.
Risk Group 2
moderate
individual
risk,
low community
risk
A pathogen that can cause human or animal disease but is unlikely
to be a serious hazard to laboratory workers, the community,
livestock or the environment. Laboratory exposures may cause
serious infection, but effective treatment and preventive measures
are available and the risk of spread of infection is limited.
Risk Group 3
high
individual
risk,
low
community risk
A pathogen that usually causes serious human or animal disease but
does not ordinarily spread from one infected individual to another.
Effective treatment and preventive measures are available.
Risk Group 4
high
individual
and community
risk
A pathogen that usually causes serious human or animal disease and
that can be readily transmitted from one individual to another,
directly or indirectly. Effective treatment and preventive measures
are not usually available.
Table 5: Classification of host (micro-) organisms by risk groups (NIH 2013)
As any new technique may represent a risk to human, animal or environmental health Synthetic Biology is
subject to specific regulations in order to perform research in a responsible and safe way (Check 2005). This
circumstance is of special relevance for projects intended to be released into the environment or for
commercial use.
The focus of risk assessment of constructs designed with BioBricks™ has usually been put on laboratory safety
based upon biosafety guidelines as published by the NIH (NIH guidelines for research involving recombinant or
synthetic nucleic acid molecules) (NIH 2013) and WHO (Laboratory biosafety manual) (WHO 2004).
However, a biosafety level designation is not exclusively based upon the classification of the host organism but
is a composite of design features, construction, containment facilities, equipment, practices and operational
procedures required for working with agents from the various risk groups as displayed in Table 6.