Beyond Antimicrobial Resistance: Evidence for a Distinct Role of the AcrD Efflux Pump in
            <i>Salmonella</i>
            Biology

Buckner, Michelle M. C.; Blair, Jessica M A; Ragione, Roberto M. La; Newcombe, Jane; Dwyer, Daniel J.; Ivens, Alasdair; Piddock, Laura J. V.

doi:10.1128/mbio.01916-16

Cited by 44 publications

(32 citation statements)

References 73 publications

(104 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Broader metabolic changes were also noted, including altered carbon and amino acid metabolism (35). An elevated basal expression of farE in response to accumulation of cellular metabolites would be consistent with observations that other RND family efflux pumps also exhibit increased expression in response to an accumulation of cellular metabolites (36)(37)(38)(39).…”

Section: Discussionsupporting

confidence: 83%

DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus

et al. 2019

View full text Add to dashboard Cite

Divergent genes in Staphylococcus aureus USA300 encode the efflux pump FarE and TetR family regulator FarR, which confer resistance to antimicrobial unsaturated fatty acids. To study their regulation, we constructed USA300 ΔfarER, which exhibited a 2-fold reduction in MIC of linoleic acid. farE expressed from its native promoter on pLIfarE conferred increased resistance to USA300 but not USA300 ΔfarER. Complementation of USA300 ΔfarER with pLIfarR also had no effect, whereas resistance was restored with pLIfarER or through ectopic expression of farE. In electrophoretic mobility shift assays, FarR bound to three different oligonucleotide probes that each contained a TAGWTTA motif, occurring as (i) a singular motif overlapping the −10 element of the PfarR promoter, (ii) in palindrome PAL1 immediately in the 3′ direction of PfarR, or (iii) within PAL2 upstream of the predicted PfarE promoter. FarR autorepressed its expression through cooperative binding to PAL1 and the adjacent TAGWTTA motif in PfarR. Consistent with reports that S. aureus does not metabolize fatty acids through acyl coenzyme A (acyl-CoA) intermediates, DNA binding activity of FarR was not affected by linoleoyl-CoA. Conversely, induction of farE required fatty acid kinase FakA, which catalyzes the first metabolic step in the incorporation of unsaturated fatty acids into phospholipid. We conclude that FarR is needed to promote the expression of farE while strongly autorepressing its own expression, and our data are consistent with a model whereby FarR interacts with a FakA-dependent product of exogenous fatty acid metabolism to ensure that efflux only occurs when the metabolic capacity for incorporation of fatty acid into phospholipid is exceeded. IMPORTANCE Here, we describe the DNA binding and sensor specificity of FarR, a novel TetR family regulator (TFR) in Staphylococcus aureus. Unlike the majority of TFRs that have been characterized, which function to repress a divergently transcribed gene, we find that FarR is needed to promote expression of the divergently transcribed farE gene, encoding a resistance-nodulation-division (RND) family efflux pump that is induced in response to antimicrobial unsaturated fatty acids. Induction of farE was dependent on the function of the fatty acid kinase FakA, which catalyzes the first metabolic step in the incorporation of exogenous unsaturated fatty acids into phospholipid. This represents a novel example of TFR function.

show abstract

Section: Discussionsupporting

confidence: 83%

DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Not surprisingly, S. enterica mutants lacking AcrAB‐TolC are avirulent upon infection of immunodeficient mice, which involves colonization of the hepatobiliary tract (Stone and Miller, ; Lacroix et al ., ; Nishino et al ., ). However, sensitivity to bile is not only cause of attenuation as the AcrAB‐TolC system plays multiple roles in bacterial physiology and virulence (Piddock, ; Sun et al ., ; Buckner et al ., ; Wang‐Kan et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Adaptation of Salmonella enterica to bile: essential role of AcrAB‐mediated efflux

Urdaneta

Casadesús

2018

Environmental Microbiology

View full text Add to dashboard Cite

Adaptation to bile is the ability to endure the lethal effects of bile salts after growth on sublethal concentrations. Surveys of adaptation to bile in Salmonella enterica ser. Tyhimurium reveal that active efflux is essential for adaptation while other bacterial functions involved in bile resistance are not. Among S. enterica mutants lacking one or more efflux systems, only strains lacking AcrAB are unable to adapt, thus revealing an essential role for AcrAB. Transcription of the acrAB operon is upregulated in the presence of a sublethal concentration of sodium deoxycholate (DOC) while other efflux loci are either weakly upregulated or irresponsive. Upregulation of acrAB transcription is strong during exponential growth, and weak in stationary cultures. Single cell analysis of ethidium bromide accumulation indicates that DOC-induced AcrAB-mediated efflux occurs in both exponential and stationary cultures. Upregulation of acrAB expression may thus be crucial at early stages of adaptation, while sustained AcrAB activity may be sufficient to confer bile resistance in nondividing cells.

show abstract

“…Genomes of Gram-negative bacteria encode multiple RND-transporters which pair with a number of PAPs forming a variety of efflux systems with different substrate profiles and distinct cellular roles [8,[10][11][12][13][14][15]. Salmonella has five RND transporters (AcrB, AcrD, AcrF, MdtB/ C and MdsB) while E. coli has six and Pseudomonas aeruginosa has more than ten.…”

Section: Introductionmentioning

confidence: 99%

Identification of binding residues between periplasmic adapter protein (PAP) and RND efflux pumps explains PAP-pump promiscuity and roles in antimicrobial resistance

et al. 2019

Self Cite

View full text Add to dashboard Cite

Active efflux due to tripartite RND efflux pumps is an important mechanism of clinically relevant antibiotic resistance in Gram-negative bacteria. These pumps are also essential for Gram-negative pathogens to cause infection and form biofilms. They consist of an inner membrane RND transporter; a periplasmic adaptor protein (PAP), and an outer membrane channel. The role of PAPs in assembly, and the identities of specific residues involved in PAP-RND binding, remain poorly understood. Using recent high-resolution structures, four 3D sites involved in PAP-RND binding within each PAP protomer were defined that correspond to nine discrete linear binding sequences or "binding boxes" within the PAP sequence. In the important human pathogen Salmonella enterica, these binding boxes are conserved within phylogenetically-related PAPs, such as AcrA and AcrE, while differing considerably between divergent PAPs such as MdsA and MdtA, despite overall conservation of the PAP structure. By analysing these binding sequences we created a predictive model of PAP-RND interaction, which suggested the determinants that may allow promiscuity between certain PAPs, but discrimination of others. We corroborated these predictions using direct phenotypic data, confirming that only AcrA and AcrE, but not MdtA or MsdA, can function with the major RND pump AcrB. Furthermore, we provide functional validation of the involvement of the binding boxes by disruptive site-directed mutagenesis. These results directly link sequence conservation within identified PAP binding sites with functional data providing mechanistic explanation for assembly of clinically relevant RND-pumps and explain how Salmonella and other pathogens maintain a degree of redundancy in efflux mediated resistance. Overall, our study provides a novel understanding of the molecular determinants driving the RND-PAP recognition by bridging the available structural information with experimental functional validation thus providing the scientific community with a

show abstract

Beyond Antimicrobial Resistance: Evidence for a Distinct Role of the AcrD Efflux Pump in Salmonella Biology

Cited by 44 publications

References 73 publications

DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus

DNA Binding and Sensor Specificity of FarR, a Novel TetR Family Regulator Required for Induction of the Fatty Acid Efflux Pump FarE in Staphylococcus aureus

Adaptation of Salmonella enterica to bile: essential role of AcrAB‐mediated efflux

Identification of binding residues between periplasmic adapter protein (PAP) and RND efflux pumps explains PAP-pump promiscuity and roles in antimicrobial resistance

Contact Info

Product

Resources

About