Fonticins are phage tail-like bacteriocins produced by the Gram-negative bacterium Pragia fontium from the family Budviciaceae. This bacterium produces contractile-type particles that adsorb on the surface of sensitive bacteria and penetrate the cell wall, probably during contraction, in a way similar to the type VI secretion system. We characterized the pore-forming activity of fonticins using both living cells and in vitro model membranes. Using a potassium leakage assay, we show that fonticins are able to permeabilize sensitive cells. On black lipid membranes, single-pore conductance is about 0.78 nS in 1 M NaCl and appears to be linearly dependent on the increasing molar strength of NaCl solution, which is a property of considerably large pores. In agreement with these findings, fonticins are not ion selective for Na+, K+, and Cl-. Polyethylene glycol 3350 (PEG 3350) molecules of about 3.5 nm in diameter can enter the fonticin pore lumen, whereas the larger molecules cannot pass the pore. The size of fonticin pores was confirmed by transmission electron microscopy. The terminal membrane-piercing complex of the fonticin tube probably creates a selective barrier restricting passage of macromolecules. IMPORTANCE Phage tail-like bacteriocins are now the subject of research as potent antibacterial agents due to their narrow host specificity and single-hit mode of action. In this work, we focused on the structure and mode of action of fonticins. According to some theories, related particles were initially adapted for passage of double-stranded DNA (dsDNA) molecules, but fonticins changed their function during the evolution; they are able to form large pores through the bacterial envelope of Gram-negative bacteria. As various pore-forming proteins are extensively used for nanopore sequencing and stochastic sensing, we decided to investigate the pore-forming properties of fonticin protein complexes on artificial lipid membranes. Our research revealed remarkable structural properties of these particles that may have a potential application as a nanodevice.

• Klíčová slova
• black lipid membranes, conductance, electric current, electron microscopy, fonticin, membrane pore formation, phage tail-like bacteriocins, single-pore conductance,
• MeSH
• bakteriociny * metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• chlorid sodný metabolismus   MeSH
• Enterobacteriaceae MeSH
• Gammaproteobacteria MeSH
• lipidové dvojvrstvy * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriociny * MeSH
• chlorid sodný MeSH
• lipidové dvojvrstvy * MeSH

Striking differences in the production of specific inhibitory agents affecting other strains of the same (or of related) species were found between genera of the family Enterobacteriaceae. We tested 50-163 strains each of the potentially pathogenic genera: Escherichia, Citrobacter, Enterobacter, Kluyvera, and Leclercia for their ability to produce bacteriophages, high-molecular-weight (HMW) and low-molecular-weight (LMW) bacteriocins and siderophores against the same sets of strains, using the cross-test method. The genus Escherichia differs substantially from all other Enterobacteriaceae, harboring a notable proportion of lysogenic (36.6%) and colicinogenic (13.9%) strains. Only 18.2% of the Citrobacter strains are lysogenic and only rarely are they colicinogenic, although in 7.3%, they produce phage tail-like bacteriocins. On the other hand, Kluyvera strains were only in 1.8% lysogenic, no colicinogenic strains were found, but in 7.3%, they produced siderophores causing zones of growth inhibition in agar cultures of strains of the same genus. In Leclercia, 10.0% of the strains were lysogenic, 2.0% produced HMW bacteriocins, no colicinogenic strains were found and 2.0% produced siderophores. Enterobacter has shown 23.1% of strains producing siderophores, whereas merely 7.7% were lysogenic, 1.9% colicinogenic and 3.8% formed phage tail-like bacteriocins. HMW bacteriocins of Enterobacter strains disposed of an unusually wide spectrum of activity. The siderophore activity spectrum was rather wide in any genus, but the siderophores were usually not produced by strains producing phages or colicins.

• MeSH
• antibakteriální látky biosyntéza   MeSH
• bakteriociny biosyntéza   MeSH
• bakteriofágy fyziologie   MeSH
• Enterobacteriaceae klasifikace   metabolismus   virologie   MeSH
• incidence MeSH
• koliciny metabolismus   MeSH
• kultivační média MeSH
• lidé MeSH
• lyzogenie MeSH
• molekulová hmotnost MeSH
• siderofory metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• bakteriociny MeSH
• koliciny MeSH
• kultivační média MeSH
• siderofory MeSH