Joan Slonczewski: September 2011 Archives

Last post, someone asked whether we've gone beyond molecules to engineer development of an organism. Molecules are what runs development--molecules made by genes. Consider the homeobox HOX genes (which Charlie mentions in Glasshouse). The same fundamental set of HOX molecules turn on development for the fruit fly, the mouse, and the human.

Picking a drug-producing bacterium off a bar counter is one thing. But would we pick a baby because it makes one molecule?

We already do. Suppose your child has an incurable defect, a single broken gene that fails to make one protein. In some cases, the child can be "cured" by stem cells from the umbilical cord of a matched relative. To get the stem cells, you fertilize in vitro, and grow the embryos in a dish. Then pick the one with the right gene that makes the right protein. So that embryo gets implanted, and when s/he is born, the umbilical cord blood cures the sibling. But what about those other embryos in the dish?

In The Highest Frontier, parents pick genes to make their kids look like Paul Newman; and so the entering class is full of Newmans. But to make synthetic babies, why stop with what's human? I once asked Francis Collins, before an audience of a thousand industrial chemists, whether we should improve humans using chimp genes, since the chimp has a stronger immune system. He gave me a look of horror, then took the next question.

Whatever genes we choose, cord blood won't always do. Suppose it's a brain defect, or a cancer? Then we need to carry the gene in with something really good at infecting cells--HIV. The main media refused to actually name AIDS virus for several weeks; it took a comic strip and SF blogs to say it. Of course, the lentiviral vector can't be one that actually causes AIDS; it has to be stripped down and modified for safety. The way you make it safe is (1) gut out the AIDS-causing genes, (2) add animal virus regulators, such as from woodchuck hepatitis virus and cow respiratory virus. Just hope you're not a woodchuck.

Would you like to have chimp genes to fight cancer and malaria? Or maybe kudzu genes for antioxidants?

Could microbes grow the starship? Starships grow as organisms in George Zebrowski's Macrolife, and in Octavia Butler's Lilith's Brood. A single cell could multiply into a living starship made of trillions of cells. The starship could divide and form a whole fleet of them, enough to sustain generations of human travelers. Any damage could be repaired, since every cell's DNA would contain all the blueprint of the entire structure. Our own teeth grow biofilms that survive decades of brushing and dentistry--maybe they could survive outer space.

So far, most synthetic biology looks at one molecule at a time. Synthetic biology basically extends what microbiologists call the fermentation industry. The original fermentation product was ethanol, in yeast-fermented beverages that kept water safe to drink. Today, microbes make all kinds of products, most notably antibiotics like penicillin. Pharma companies send explorers to remote parts of the globe to find exotic drug-producing strains. My students discovered a new drug producer growing from a crack in a bar counter at the local college hangout. To prove it, they first spread tester bacteria on a Petri plate; then spotted four different bar isolates on top of the testers. The isolate at left shows a clear ring where its antibiotic diffused out and killed the tester. We don't yet know what the antibiotic is, but if it's new we could patent it for Kenyon.

We imagine making products "not found in nature"--but even natural microbes make molecules that organic chemists would never dream of. Look at this antitumor agent discovered from a filamentous soil bacterium, the kind of bacteria that give soil that new smell in the springtime (Science 297:1170). Those sets of three parallel lines are each triple bonds, within a nine-carbon ring. Who would even think to draw such a thing, let alone make it? To make it, the bacteria use modular enzymes, nanoscale assembly lines that condense one functional part after another. The original nanotechnology.

In principle, microbes could produce any organic molecule. In The Highest Frontier, microbial machines "print out" any molecule or complex--even viruses, unfortunately, like flu or Ebola. A new twist on "computer virus." And in Brain Plague, where the microbes grow buildings, they develop cancers--blobs of building material that crawl off to tap a power line. Still, is it worth a try to grow a microbial starship?

Thanks so much for Charlie's introduction, and for his extremely generous invitation to post here. I've enjoyed Charlie's books, especially Rule 34, and the discourse on this blog. I will see what I can come up with, while Charlie and my other lucky friends head off to a spaceship conference. And they complain of jet lag? For me just a trip to Oxford Street (from rural Ohio) would be worth the jet lag.

My book that Charlie kindly mentioned, The Highest Frontier, turned out to be controversial. Greg Benford and Don Sakers loved it, but someone else feared reading it would make himself ill, while yet another wanted to see "if the test readers live." I thought readers might pause at the zoophiles, the twin towers scene, or the gay-married college president. But the main flashpoint was salt (NaCl). Could table salt become a controlled substance?

Salt's taste and antimicrobial power run through human history. There have always been salt roads, salt taxes, and salt wars. Salt trade drove the rise of cities like Liverpool, and destroyed cities in Europe and Asia. Gandhi's independence movement began with a salt march. In America, the Iroquois called colonial Europeans "Salt Beings" for their obsession with it. Today, in modern medicine, the salt wars continue.

In The Highest Frontier, Jenny Ramos Kennedy is a Cuban-American student-athlete who goes to college in a casino-financed space habitat. She likes to capture ultraphytes (invasive UV-photosynthetic extraterrestrials) and keep them in the cellar, just as kids today keep skunks or pythons. But unlike pythons, cyanide-producing ultraphytes make the bioterror list. Ultraphytes (today's colonial Salt Beings) are actually halophiles, life forms that need high salt. To curb the spread of ultraphytes, Homeworld Security controls salt. If that sounds about as useful as controlling toothpaste in your carry-on, read and find out.

The orbital spacehab is something I'd like to learn more about. Could an orbital spacehab really get made by 2100? Engineering is not my field, but from the Wright brothers to commercial jets took 50 years. Today, the International Space Station does surprisingly well with pathetic investment; what if someone were to stake more? I wonder if the folks who built Vegas could put something more outrageous in space. And when the government outlaws vice on Earth, they'll need someplace off-world to keep it--and tax it.

What most interests me space biology. My microbiology textbook opens with the Mars Phoenix lander. Could we grow space lift cables as bacterial cell walls? Some bacteria related to anthrax already grow as thread-like macrofibers, which genetic engineering might convert to nanotubes. The cables would be self-healing, amid all that Kessler debris. Could photosynthetic bacteria run fuel cells and make hydrogen? This is no longer fiction, it's science today. Could solar microbes someday power a space habitat? We need power generation off-world, the sooner the better, because all large-scale energy sources have large downsides for planet Earth.

Have to run and check my drug-resistant bacteria, but let me know if the test readers live.



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