Antisense peptide nucleic acids (PNAs) can specifically inhibit Escherichia
coli gene expression and growth and hold promise as anti-infective agents
and as tools for microbial functional genomics. Here we demonstrate that ch
emical modification improves the potency of standard PNAs. We show that 9-
to 12-mer PNAs, especially when attached to the cell wall/membrane-active p
eptide KFFKFFKFFK, provide improvements in antisense potency in E. coli amo
unting to two orders of magnitude while retaining target specificity. Pepti
de-PNA conjugates targeted to ribosomal RNA (rRNA) and to messenger RNA (mR
NA) encoding the essential fatty acid biosynthesis protein Acp prevented ce
ll growth. The anti-acpP PNA at 2 muM concentration cured HeLa cell culture
s noninvasively infected with E. coli K12 without any apparent toxicity to
the human cells. These results indicate that peptides can be used to carry
antisense PNA agents into bacteria. Such peptide-PNA conjugates open exciti
ng possibilities for anti-infective drug development and provide new tools
for microbial genetics.