Cadaverine Suppresses Persistence to Carboxypenicillins in Pseudomonas aeruginosa PAO1

Abstract

The refractory nature of Pseudomonas aeruginosa infections is due in part to the presence of specialized cells, termed persisters, within the population. To identify genes involved in P. aeruginosa persister formation, a PAO1 transposon (Tn) library was challenged en masse with 1,000 g/ml of carbenicillin and was enriched for mutants that were able to survive in the presence of this antibiotic. For one mutant that was further characterized, the carbenicillin MIC was equal to that of PAO1, but persister formation exhibited a 20-fold increase after exposure to the antibiotic. Sequence analysis revealed that the Tn had inserted into PA4115, a gene encoding a putative lysine decarboxylase. A PA4115 mutant that produced 48-fold and 20-fold more survivors than PAO1 after 10-h exposures to carbenicillin and ticarcillin, respectively, was generated by allelic exchange. Furthermore, the rate of carboxypenicillin-induced lysis was reduced in the PA4115 mutant. Under certain pH conditions, lysine decarboxylase converts lysine to cadaverine. By measuring cadaverine production, we discovered that the PA4115 mutant had significantly reduced lysine decarboxylase activity. To determine if reduced cadaverine levels are responsible for the increase in carbenicillin and ticarcillin persistence, viability and lysis assays were performed in the presence of exogenous cadaverine. Cadaverine increased the rate of killing and lysis of the PA4115 mutant in the presence of both antibiotics. These findings suggest that cadaverine may be able to enhance the effectiveness of carboxypenicillins against P. aeruginosa by reducing persister formation.

Dynamic Proteome Response of Pseudomonas aeruginosa to Tobramycin Antibiotic Treatment

“…For instance, supplementing 0.4% L-arginine in tryptic soy agar plate enhances the tobramycin killing of P. aeruginosa biofilm colonies over 10-fold (44). Conversely, the presence of 20 mM cadaverine (a decarboxylation product of lysine amino acid) promotes P. aeruginosa resistance to aminoglycoside kanamycin and gentamycin by fourfold (45), while suppressing its resistance to carboxypenicillins (46). Although much still needs to be understood, the results demonstrated here show that bacterial cells exposed to low levels of tobramycin exhibit increased levels of enzymes that metabolize and synthesize amino acids that could alter drug sensitivity.…”

Age of Inoculum Strongly Influences Persister Frequency and Can Mask Effects of Mutations Implicated in Altered Persistence

“…The relative nature of persisters has been noticed before (24)(25)(26)47). The decreased number of persisters in a phoU deletion mutant was evident only under certain conditions (24), and results with sucB and ubiF deletion strains prompted the authors to propose a concept of "deep" and "shallow" persisters (25).…”

Identification of a novel subfamily of bacterial AAT-fold basic amino acid decarboxylases and functional characterization of its first representative:Pseudomonas aeruginosaLdcA

“…This conclusion was unexpected considering that the product of another gene, PA4115 , was previously reported to be responsible for 25% of Cad production in overnight cultures grown in the same medium as the one used in our assays, and therefore proposed to be an Ldc (Manuel et al ., 2010). After carboxypenicillin treatment, the PA4115 mutant exhibited an increased number of persisters that was significantly reduced upon addition of exogenous Cad, further supporting the hypothesis of PA4115 being an Ldc (Manuel et al ., 2010). Yet, our careful inspection of its sequence revealed that PA4115 belongs to the family of Lonely Guy (LOG) proteins because it contains a highly conserved PGGxGTxxE motif and a nucleotide-binding Rossmann fold.…”

“…In our quest for deciphering the importance of LdcA in bacterial physiology, we analyzed the role of its product Cad shown to play a fundamental role in P. aeruginosa virulence. Indeed, this polyamine was reported to be involved in the persistence of the bacterium which is of importance for its eradication by antibiotics; specifically, Cad production was shown to lead to a reduction of the dormant cells that form an antibiotic-tolerant subpopulation in MH medium (Manuel et al , 2010).…”