Synthetic Biology | State of the Art
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BioBrick™ parts
Description
Promoters
Recruitment sites for transcription machinery RNA Polymerase
binding sites
Ribosome binding sites
Region on mRNA for ribosomal binding translation initiation
Protein domains
Encodes functional compartments of
protein sequence
Protein coding sequences
Encodes the amino acid sequence of a protein
Translational units
Translational units are composed of a ribosome binding site and
a protein coding sequence. They begin at the site of translational
initiation, the RBS, and end at the site of translational
termination, the stop codon.
Terminators
Transcription stop signal at the end of
a gene or operon
DNA
DNA parts provide functionality to the DNA itself. DNA parts
include cloning sites, scars, primer binding sites, spacers,
recombination sites, conjugative transfer elements, transposons,
origami, and aptamers.
Plasmid backbones
A plasmid is a circular, double-stranded DNA molecule typically
containing a few thousand base pairs that replicate within the
cell independently of the chromosomal DNA. A plasmid backbone
is defined as the plasmid sequence beginning with the BioBrick™
suffix, including the replication origin and antibiotic resistance
marker, and ending with the BioBrick™ prefix.
Plasmids
A plasmid is a circular, double-stranded DNA molecule typically
containing a few thousand base pairs that replicate within the
cell independently of the chromosomal DNA. If you're looking for
a plasmid or vector to propagate or
assemble plasmid backbones,
please see the set of plasmid backbones. There are a few parts in
the Registry that are only available as circular plasmids, not as
parts in a plasmid backbone. Note that these plasmids largely do
not conform to the BioBrick™ standard.
Primers
A primer is a short single-stranded DNA sequence used as a
starting point for PCR amplification or sequencing. Although
primers are not actually available via the Registry distribution,
commonly used primer sequences are included.
Composite parts
Composite parts are combinations of two or more BioBrick™
parts.
Table 3: Types of parts available from the BioBrick™ Registry Repository (modified from iGEM (2014)).
Synthetic Biology | Applications of Synthetic Biology
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4
Applications of
synthetic biology
Synthetic biology has a vast range of potential practical applications (Porcar and Pereto 2012). It is perceived
as a way to tackle problems, among others, in cell and tissue engineering, gene therapy, biologically derived
materials, biocatalysis and natural product synthesis (Arkin and Fletcher 2006). In addition, it is believed to
facilitate mass production of useful compounds and a variety of chemicals (drugs, biofuels, etc.), to be key in
the development of bioremediation, to increase crop yield, lead to the production of novel food ingredients,
and improve human health (Porcar and Pereto 2012). Upon careful design, it offers the possibility to minimise
unwanted (side) effects (like production of any undesirable substances that might reduce yield or inhibit
metabolic pathways), to reduce energy costs to the cells, and to establish good conversion from substrate(s) to
desired product (Ellis and Goodacre 2012).
Major efforts toward potential application of synthetic biology include the production of biofuels like ethanol,
algae-based fuels, bio-hydrogen and microbial fuel cells; bioremediation like wastewater treatment, water
desalination, solid waste decomposition and CO
2
recapturing; the production of biomaterials like bioplastics,
bulk chemicals, pharmaceuticals, flavourings, fragrances, and compounds for cosmetics; and finally the
production of novel cells and organisms, which includes the generation of protocells and xenobiology (see CBD
(2014) and OECD (2014) for excellent recent overviews).
4.1
Synthetic biology in microorganisms
Device or system design is done in context of a particular host cell (Kitney and Freemont 2012). The major
model microbial species in which the foundational work in synthetic biology (
i.e. metabolic engineering and
minimal genome construction) was carried out have been
Escherichia coli and
Saccharomyces cerevisiae
(Cameron et al. 2014). Fabrication facilities (biofabs) are developed to construct, characterise and standardise
biological components for widely used platform organisms (Nielsen and Keasling 2011). The big advantage of
concentrating on a few organisms is obviously that much knowledge is accumulated, allowing for better
prediction of the results of engineering strategies.
Microbes, in particular
Escherichia coli or yeast, may also be used as experimentally convenient heterologous
hosts to reconstitute biosynthesis (Li and Pfeifer 2014). Such an approach offers considerable advantages as
compared to production in, e.g., the native plant host or chemical synthesis strategies, which may be
hampered by slow growth kinetics and low native titres. Companies design strains (e.g.
Escherichia coli Clean
Genome®, Scarab Genomics) with “enhanced genetic stability, improved metabolic efficiency and improved
production yields” with the aim of creating efficient production platforms. The desired properties are achieved
by deleting nonessential gene, insertion sequence (IS) elements, recombinogenic/mobile DNA, cryptic viruses
and virulence genes, and the strains are being offered as a platform to optimise processes for the production
of, e.g., therapeutic proteins, plasmid DNA and vaccines. Also
Saccharomyces cerevisiae is already well
adapted to industrial conditions and thus its use for industrial production is easy and straight-forward (“plug-
and-play solution”) (Nielsen and Keasling 2011).
Remarkably both
Escherichia coli and
Saccharomyces cerevisiae are in addition important model organisms,
ensuring the availability of an impressing amount of data originating from basic research. Not least,
mathematical models for systems biology have been developed for them, potentially allowing for the
modelling of the interaction between all the components in the system. Finally, powerful synthetic biology
tools have been demonstrated within these two species (Montague et al. 2012). The major limitation is that
important metabolic and biological tools are absent – e.g. traits of photosynthesis or the capacity to express
large mammalian genes exhibiting splicing and post-translational modifications that both involve many genes