The role of the N-acetylglucosamine phosphoenolpyruvate phosphotransferase system from Lactobacillus plantarum 8014 in the mechanism of action of glycocin F : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry at Massey University, Manawatū, New Zealand
The rise in antibiotic-resistant bacteria is becoming a severe public health problem because
of the shortage of new antibiotics to combat existing resistant bacterial pathogens.
Should this trend of increasing bacterial drug resistance continue, the previously treatable
conditions may once again become fatal. Using broad-spectrum antibiotics causes
collateral damage to the commensal microbiota of the host leading to complications and
a greater susceptibility to opportunistic pathogenic infection. As a result, narrow spectrum
antibacterials effective against specific pathogens, are becoming increasingly sought
after. Among the many alternative classes of narrow-spectrum antibiotics, is a diverse
group of ribosomally-synthesised antimicrobial peptides known as bacteriocins. Glycocin
F (GccF), a rare and uniquely diglycosylated bacteriocin produced by Lactobacillus
plantarum KW80, appears to target a specific N-acetylglucosamine (GlcNAc) phosphotransferase
system (PTS) and causes almost instant bacteriostasis by an as yet unknown
mechanism. This thesis demonstrates how the GlcNAc-PTS is involved in the GccF mechanism
of action and that the gccH gene provides immunity to GccF. Using transgenic and
gene editing techniques, regions of the GlcNAc-PTS were either removed or altered to
prevent normal function before being tested in vivo. The results demonstrated that only
the EIIC domain of the GlcNAc-PTS is required in the GccF mechanism of action and that
it acts like a "lure" that attracts the bacteriocin to the main target that is as yet unknown.
Furthermore, the immunity gene was discovered, and using PTS knockout cell lines the
immunity mechanism was shown to act independently of the GlcNAc-PTS. This work
will form the foundation for the work needed to unravel the bacteriostatic mechanism of
action of GccF, which may lead to the development a novel antimicrobial agent.