P.C. Shannon

I was joking around with some classmates the other day and hypothesized that a professor had engineered his E. coli to produce crack. I thought about it a little more, what would it take for a bacteria to produce cocaine?

It’s not a protein, so you can’t just clone the gene for it. There has to be some biochemical pathway to produce it, and fortunately, that pathway already exists in cocoa plants. So could you clone the genes for the enzymes in that pathway into your bacteria of choice and get coke out of it? It’s probably not that simple. There are indubitably some peculiarities in the functioning of the enzymes that will get lost in the translation from plants to bacteria. Then there’s the matter of purifying your product.

Sure, it’s theoretically possible. But it would be wise to try the idea out on something that’s not illegal.

Along with the phage idea from a few days ago, I was thinking about how you would synthesize really big pieces of DNA with a novel sequence from scratch. Obviously we can produce oligos but it’s just not practicle (nor feasible I would think) to build really long pieces this way. I can’t remember if this is an idea i had or (more likely) something someone else came up with and I just can’t recall where I’ve seen it before.

You could synthesize a lot of oligos (maybe 20-mers) for your sequence and the complementary strand. The oligo would be designed such that the breaks in one strand fall in the middle of an oligo for the other strand, crudely diagrammed thusly:

BBBBBBBBBB BBBBBBBBBB BBBBBBBBBB
BBBBB BBBBBBBBB BBBBBBBBBB BBBBB

For best results, the gaps could even span multiple bases in the antisense strand. Mix with some PolIII and ligase, repeat until sufficiently long DNA.

I started reading this article yesterday about using bacteriophages to treat infections, especially strains that are resistent to most antibiotics. The great thing about phages is that they can be built entirely from their DNA. Cellular processes depend on having a progenitor — one cell becomes two becomes four. It’s been a very long time since nothing became one cell. But a bacteriophage is described entirely by its DNA; no other part of the virus enters the host. (Many viruses of higher organisms, HIV for instance, contain enzymes within in the virus particle that are required to complete their life cycle. Thus the entire virus must enter the host cell.)

The other exciting thing about phages is that they are lytic — they destroy their host. So I started thinking about ways to hijack their lifecycles. It’s routine to clone a gene who’s protein you’re interested in, overexpress it in E. coli and then purify the protein. But it can be tricky to get the protein out of the bacteria. Wouldn’t it be simpler if the bacteria broke open once they filled up with the protein? It seems like you could clone the protein into a phage genome and let it go to town.

That’s pretty academic, though. Consider a patient who’s got a nasty bacterial infection, one that’s resistent to antibiotics. You could attack with phage and it would be all good, but what if we could get those bacteria to produce something else while they’re being destroyed by the phages. You’d have 1% of your phages actually be pseudo-phages, virus particles that contain non-viral DNA that encodes some other product. This other product could be a painkiller or perhaps a cytokine or other compund to boost the immune system.