The soluble pyocins S2 and S4 from Pseudomonas aeruginosa bind to the same FpvAI receptor

Abstract

Soluble (S‐type) pyocins are Pseudomonas aeruginosa bacteriocins that kill nonimmune P. aeruginosa cells by gaining entry via a specific receptor, which, in the case of pyocin S2, is the siderophore pyoverdine receptor FpvAI, and in the case of pyocin S3, FpvAII. The nucleic acid sequence at the positions 4327697–4327359 of P. aeruginosa PAO1 genome was not annotated, but it was predicted to encode the immunity gene of the flanking pyocin S4 gene () based on our analysis of the genome sequence. Using RT‐PCR, the expression of the immunity gene was detected, confirming the existence of an immunity gene overlapping the S4 pyocin gene. The coding for pyocin S4 and the downstream gene coding for the immunity protein were cloned and expressed in Escherichia coli and the His‐tagged S4 pyocin was obtained in pure form. Forty‐three P. aeruginosa strains were typed via PCR to identify their ferripyoverdine receptor gene (fpvAI–III) and were tested for their sensitivity to pyocin S4. All S4‐sensitive strains had the type I ferripyoverdine receptor fpvA gene. Some S4‐resistant type I fpvA‐positive strains were detected, but all of them had the S4 immunity gene, and, following the deletion of the immunity gene, became S4‐sensitive. The fpvAI receptor gene was deleted in a S4‐sensitive strain, and, as expected, the mutant became resistant to S4. The N‐terminal receptor binding domain (RBD) of pyocin S2, which also uses the FpvAI receptor to enter the cell, was cloned in the pET‐15b vector, and expressed in E. coli. When the purified RBD was mixed with pyocin S4 at different ratios, an inhibition of killing was observed, indicating that S2 RBD competes with the pyocin S4 for the binding to the FpvAI receptor. The S2 RBD was also shown to enhance the expression of the pvdA pyoverdine gene, suggesting that it, like pyoverdine, works via the known siderophore‐mediated signalization pathway.

The deletion of TonB-dependent receptor genes is part of the genome reduction process that occurs during adaptation ofPseudomonas aeruginosato the cystic fibrosis lung

“…It has been shown that different S-type pyocins utilize TonB-dependent receptors involved in iron uptake to enter P. aeruginosa cells (Baysse et al, 1999;Denayer et al, 2007;Elfarash et al, 2012Elfarash et al, , 2014. In fact, negative selection pressure exerted on fpvA and fptA, both deleted in P. aeruginosa DK2 isolates, could have been caused by the pyocins S2/S4 and S5, respectively (Denayer et al, 2007;Elfarash et al, 2012Elfarash et al, , 2014. A P. aeruginosa strain harboring the immunity gene for the pyocin produced by the co-colonizing strain and producing itself a pyocin to which the latter is sensitive could lead to the outcompetition of that particular P. aeruginosa clone.…”

“…It has been observed that during the colonization of P. aeruginosa in the CF lung, pyoverdine-negative mutants can accumulate (De Vos et al, 2001;Lamont et al, 2009), indicating either that its production is too energetically costly or that there might be a selection pressure acting on this siderophore in these conditions. This is the case for pyocins S2/S4 and S3, which use FpvAI and FpvAII as receptors, respectively (Baysse et al, 1999;Denayer et al, 2007;Elfarash et al, 2012), while the pore-forming pyocin S5 utilizes the FptA ferripyochelin receptor (Elfarash et al, 2014). Interestingly, several S-pyocins (soluble pyocins) target ferrisiderophore receptors to gain entry to the cells and kill them.…”

Structural Determinants for Activity and Specificity of the Bacterial Toxin LlpA

“…The S-type pyocins of Pseudomonas aeruginosa share structural and functional features with Escherichia coli colicins [15]. Following docking onto surface-exposed targets such as siderophore receptors [16], [17], S-pyocins kill cells by nucleic acid degradation [10], [17], cytoplasmic membrane damage [18], or inhibition of peptidoglycan synthesis [19], [20]. Putidacin A (or LlpA BW ), first identified in Pseudomonas putida BW11M1 [21], represents a class of Pseudomonas -specific antibacterial proteins not related to any known bacteriocin.…”

Inhibition of food-related bacteria by antibacterial substances produced by Pseudomonas sp. strains isolated from pasteurized milk

“…Some Pseudomonas aeruginosa strains, for example, produce AMS called pyocins (MICHEL-BRIAND and BAYSSE, 2002;ELFARASH et al, 2012).…”

“…In food and drinks, the addition of antimicrobial compounds to processed products has become a powerful weapon in the arsenal of food preservation. These compounds, especially the bacteriocins, can be interesting strategies against the growth of undesirable microorganism (RILEY and WERTZ, 2002;ELFARASH et al, 2012, NISHIE et al, 2012.…”