Growth-related changes in intracellular spermidine and its effect on efflux pump expression and quorum sensing in Burkholderia pseudomallei

Abstract

The Burkholderia pseudomallei BpeAB-OprB resistance-nodulation-division (RND) family pump effluxes aminoglycoside and macrolide antibiotics as well as acylhomoserine lactones (AHLs) involved in quorum sensing. Expression of bpeA-lacZ was cell density-dependent and was inducible in the presence of these compounds. Intracellular levels of spermidine and N-acetylspermidine increased with cell density in wild-type B. pseudomallei KHW, but were always lower in the bpeAB pump mutant at all growth phases. The significance of changes in intracellular spermidine on efflux pump expression was demonstrated by the disruption of the binding of the BpeR repressor protein to the bpeABoprB regulatory region in vitro in the presence of increasing spermidine concentrations. This was supported by dose-dependent activation of bpeA-lacZ transcription in vivo in the presence of exogenous spermidine and N-acetylspermidine, thus implicating the involvement of the BpeAB-OprB pump in spermidine homeostasis in B. pseudomallei. Consequently, inhibition of intracellular spermidine synthesis reduced the efflux of AHLs by BpeAB-OprB. Other potential therapeutic applications of spermidine synthase inhibitors include the reduction of swimming motility and biofilm formation by B. pseudomallei.

A Francisella tularensis Locus Required for Spermine Responsiveness Is Necessary for Virulence

“…Bacteria can either make their own polyamines (putrescine and spermidine) or import polyamines (spermidine, putrescine, and spermine) from the extracellular environment to grow (64). To identify mutants that were unable to utilize extracellular polyamines, we used an inhibitor of spermidine synthase, dicyclohexylamine (3,9,27,37,43). Isolates were selected from a library of mutants made with a Mariner-based transposon (50) that were unable to replicate in the presence of both the inhibitor and spermine in CDM.…”

“…The development of biofilms by Vibrio cholerae and Yersinia pestis is regulated by the concentration of extracellular polyamines (39,47,63). In addition, efflux pump expression and quorum sensing in Burkholderia pseudomallei are regulated by the presence of spermidine (9). FTL_0883 is conserved among Burkholderia, Vibrio, and Yersinia species based on a BLAST homology search, which suggests that FTL_0883 could serve as a model for the function of the homologous proteins.…”

The Antibacterial Activity of Ga3+Is Influenced by Ligand Complexation as Well as the Bacterial Carbon Source

“…Spermidine is one of the main polyamines in bacteria and has previously been shown to act as a translational regulator through several different mechanisms (26,49 (31), and inhibition of spermidine biosynthesis attenuates quorum sensing in Burkholderia pseudomallei (11). Consequently, it is likely that a decrease in spermidine levels upon exposure to Ga-Cit could contribute to the poor ability of P. aeruginosa cells to attach and form biofilms in the presence of Ga (30).…”

Non-genetic mechanisms communicating antibiotic resistance: rethinking strategies for antimicrobial drug design

“…In Burkholderia pseudomallei, spermidine upregulates efflux pumps such as BpeAB-OprB, AmrABOprB and BpeEF-OprC, contributing to aminoglycoside and macrolide resistance as well as biofilm formation through the increased efflux of N-acyl homoserine lactones [50]. Furthermore, GeneChip experiments and promoter fusion studies have shown that spermidine induces the expression of the P. aeruginosa oprH-phoPQ and PA3552-PA3559 operons encoding enzymes for LPS modification and resulting in PhoPQ-mediated spermidine-induced resistance to cationic antimicrobial peptides and quinolones [38].…”