4.9 Concluding Remarks, Challenges, and Future Directions 714.9 Concluding Remarks, Challenges, and Future Directions
Directions
Streamlined-genome E. coli strains are representatives of a promising direction
of synthetic biology research. The goals of cell simplification have already been
partially fulfilled. Reduced complexity arising from elimination of redundant and
unnecessary functions helped to elucidate hitherto unknown functions and net-
work interactions. Increased phenotypic uniformity and genetic stability can be
exploited for maintaining unstable synthetic constructs. Demonstration of
increased amino acid production by reduced-genome cells may hint at improve-
ments in cellular economy.
Numerous applications, from bacterial computation and gene network
model building to vaccine production and plasmid biopharmaceutical manu-
facturing, have been suggested for streamlined-genome E. coli. However, most
tangible applications to date were research oriented, and despite all the
advances, published biotechnological applications of streamlined-genome cells
were limited to a few pilot studies (Table 4.1). In order to attain a more wide-
spread status as production hosts, simplified cells clearly need improvements,
and superior performance over traditional production strains have to be
demonstrated.
On one hand, construction of a superior chassis should involve not only
streamlining but also extensive rational optimization. Introduction of muta-
tions known to increase fitness or compensating for loss of certain genetic
material could enhance performance. Advantageous features of different E. coli
strains (e.g., the high recombinant protein production capability of BL21 and
the easy genetic accessibility and high stability of K-12 MDS) could be com-
bined in a single host [95]. New genome manipulation techniques are at hand to
accelerate the optimization process. MAGE allows simultaneous, targeted
introduction of small modifications at many genomic sites [121]. New DNA
Table 4.1 Published biotechnology-related applications of streamlined-genome E. coli.
Application ReferencesRecombinant protein production [113–115]
Construction of lentiviral expression vectors [99]
Enhanced l-threonine production [47, 116]
Stabilized maintenance of genetic constructs [4, 5]
Expression of avian influenza virus gene [117]
Dengue reporter virus constructions [118]
Periplasmic delivery of human interleukin-10 [119]
Investigation of antimicrobial peptide sensitivity [120]
Construction of IS-free P1 phage [7]
Incorporation of unnatural amino acids in proteins [110]