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The number of bacterial cells in your body at this very moment is equivalent to the total population of your own cells. For the most part they are beneficial, preventing infection, aiding digestion, and perhaps even producing useful chemicals. These commensals, as they are called, have evolved with humans in a strongly symbiotic relationship. Clearly, our body is already conditioned to hold a vast army of prokaryotes to do its bidding. How can synthetic
biology harness this potential?

Imagine a time in the not-too distant future. Elliott wakes up in the morning to get ready for work. After taking a shower, he examines his clean, clear face in the mirror, deciding that he can probably wait another month before re-applying the bio-spray that keeps his skin pores clean and renders shaving unnecessary. The spray contains skin surface bacteria engineered to eat dirt, oil, and dead skin, as well as dissolve the keratin in facial hair, while keeping the skin intact. They also prevent colonisation by foreign bacteria that can cause infection of pores in skin, preventing acne. He looks at his old toothbrush in the medicine cabinet, and decides to throw it away. Ever since the dentist gave him the oral wash earlier in the year, he has had no use for it. The wash contained a population of bacterial cells programmed to vigorobreak down any stains or food residue, and dissolve plaque buildup. They also created a special biofilm which prevents other bacteria from colonising, eliminating halitosis and gingivitis. Elliott decided to change his breath scent, and picked up a small pen light which he set to yellow and flashed in his mouth. A few minutes later he checked his breath. Faintly sweet and citrusy, very pleasant. The bacteria had been programmed to produce different aromatic compounds. The type Elliott had washed with gave him seven popular scents to choose from.

Elliott now wanted his breakfast. He had a bowl of cereal and milk, along with a spicy southwest omelette and some sausages. He used to be wary of many foods, as he was prone to frequent indigestion, especially from spicy foods or dairy products. But since his visit to the dietician earlier this year, those problems no longer bother him. After analysing his symptoms, the doctor selected a digestive commensal from the Biobricks 3000 catalog which had been programmed for his needs. Now lactose and the irritating chemicals in most spicy foods were broken down with ease in his stomach, before they could cause any distress . An added benefit was that he no longer had to worry about food poisoning. The new commensals specifically targeted and killed any pathogens from a long list of possible food contaminants, and could even neutralize the toxins these bacteria produced. Elliott relished his new state of permanent gastrointestinal bliss.

Source: http://openwetware.org/wiki/Synthetic_Biology

To many scientists, real appeal is that this new field provides a new way to unlock the mysteries of biology. Trying to do the things that nature does - say, orchestrating the interactions of genes and proteins triggered by some external event - is a way to discover fundamental principles that govern living systems. Now a growing number of researchers are working on ways to alter the circuitry of cells. Chemical engineer Jay Keasling at the Lawrence Berkeley National Laboratory, has refitted the gut bacterium Escherichia coli with the circuitry it needs to synthesize a precursor to the powerful antimalarial drug artemisinin. If this proves to be a cheap, reliable source of the drug, it could transform the treatment of malaria.

Once synthetic biology becomes sufficiently advanced, the big application will be construction. Biological systems are great at producing large-scale structures from small beginnings: Theoretically a seed could be programmed to grow into a house.

By reducing the molecular biology of the cell to a list of standard modules with predictable behavior, professional biodesigners could engineer molecular machines in much the same way that system-on-chip designers create silicon systems. Just as a circuit designer does not need to be an expert in silicon physics and manufacturing processes, the future biodesigner will not need a detailed knowledge of biochemistry to effectively create complex biochemical machines.

Synthetic biology is now raising a lot of moral and ethical questions. Should limits be set on what is attempted? If so, what should they be and how should they be enforced? And what steps can be taken to ensure that a rogue organisation, or even a state-sponsored bioweapons programme, does not use the technology to synthesize a dangerous microbe?

Biology is the future subject where lots of fascinating developments will take place. We have no choice but to respond to these emerging ideas.