Saturday, 24 January 2015

Eleftheria terrae

I've been warning you about the imminent end of useful antibiotics as more and more pathogens become resistant to everything we have in the shot-locker.  It is decades since a really new form of antibiotic was discovered.  Big Pharma would much rather patent a me-too modification of penicillin than go out into the wide world and isolate a new bacteria killing bacterium.  One thing that puts a disheartening stop to any new frontiers gallop is the well-known fact that 99% of known bacteria cannot be cultured in the lab. We cannot make the environment on a petri-dish sufficiently complex to satisfy their fastidious requirements, that's why, for example, we call it Clostridium difficile.

Then 12 years ago Kim Lewis and Slava Epstein had a "b'god I wish I'd said that" idea and developed a product called an iChip (i as in isolation, Chip as in plastic sandwich for high-throughput data processing). Picture. This is what you do:
  • Dig up a trowelful of soil and wash off all the bacteria into a cup
  • dilute them so that each chamber in the chip has about one bacterium
  • seal the chambers with micropore filters that will allow soluble products in but keep stray bacteria out
  • pop the iChip back in the soil and see what grows
You can then take a pure sample of, say, 10 million of a particular never-before-cultured bacterium and plate them out with Staphylococcus aureus, the cause of MRSA and impetigo.  If the growth of S.aureus is inhibited you concentrate on that sample and try to chemically characterise the active principle.  Just like one of the early lab strains of E.coli was isolated from the back-passage of Andre Lwoff, so a lot of the soil samples came from the back-yard of Losee Ling, the Head of R&D at NovoBiotic Pharma, Lewis and Epstein's start-up company.

It turns out that this is a fruitful source of novel bacteriocidals, rather too fruitful in many ways because a lot of the Staph-killing products were detergents that killed everything, including human cell-lines. After a decade of bump-and-grind they have this month released details of a totally new way of killing gram-positive bacteria called Teixobactin isolated from a species they have named Eleftheria terrae. I've had cause to be snitty-snotty about the cultural shallowness of some American scientists when it comes to the naming of parts.  NovoBiotic have patriotically called their new bug Freedom [Gk] of the land [L.] but C.P. Scott, editor of The Guardian 100 years ago, was chilling "Television? The word is half Greek, half Latin. No good can come of it" in his deprecation of mixing Greek and Latin roots.  John Logie Baird sent the first (crap-quality) transatlantic TV broadcast in 1929, Scott died in 1932 before he had a chance to see how wrong he'd called it.

<geek alert>
Teixobactin (τειχω = wall) is a depsipeptide (new word for me): a compound made up of amino acids (some weird) in which some of the bonds in the chain are ester bonds not regular peptide bonds.  Like penicillin of old, Teixobactin prevents bacteria from forming a cell wall so that they leak out their innards and die.  But it's a totally different mechanism of interference in wall building and so will hopefully provide a few decades of tinkering about with the core idea to generate another family of related therapeutics.  Even now Teixobactin has huge therapeutic potential.  €5 says Lewis and Epstein get a Nobel Prize within the next ten years.

No comments:

Post a Comment