These examples show that natural products evolved
to exploit the inherent weaknesses of bacteria28, and additional compounds
that subvert important enzymes into killing devices are likely
to be discovered. Teixobactin binds to multiple targets, none of which
is a protein (Fig. 3e and Extended Data Fig. 7). Polyprenyl-coupled cell
envelope precursors, such as lipid II, are readily accessible on the outside
ofGram-positive bacteria andrepresent an ‘Achilles heel’ for antibiotic
attack28. The target of teixobactin, the pyrophosphate-sugar moiety
of thesemolecules, is highly conservedamong eubacteria. The producer
is a Gram-negative bacterium, and its outer membrane will protect it
from re-entry of the compound (Fig. 3e and Extended Data Fig. 7).
This suggests that the producer does not employ an alternative pathway
for cell wall synthesis that would protect it from teixobactin, and
which other bacteria could borrow. Resistance could eventually emerge
from horizontal transmission of a resistance mechanism from some
soil bacterium, and given the highly conserved teixobactin bindingmotif,
thiswould likely take the formof an antibioticmodifying enzyme.However,
although determinants coding for enzymes attacking frequently
found antibiotics such as b-lactams or aminoglycosides are common,
they are unknown for the rare vancomycin. The recently discovered
teixobactin is even less common than vancomycin. After its introduction
into the clinic, it took 30 years for vancomycin resistance to appear29.
The lipid II modification pathway resulting in vancomycin resistance
probably originated in the producer of vancomycin, Amycolatopsis
orientalis19. It will probably take even longer for resistance to the
better-protected teixobactin to emerge. Teixobactin is the first member
of a new class of lipid II binding antibiotics, structurally distinct
from glycopeptides, lantibiotics30,31, and defensins32. The properties of
teixobactin suggest that it evolved to minimize resistance development
by target microorganisms. It is likely that additional natural compounds
with similarly low susceptibility to resistance are present in nature and
are waiting to be discovered.