Browse AMR Genes

Explore antimicrobial resistance genes from the literature

marR

global regulator

NCBI Pathogen Isolates

Bacterial genomes carrying this gene

NCBI Reference Gene Catalog

Known alleles and reference sequences

Protein entries specific to marR

Browse AMR rules for marR

Validation StatusSupported

Overview

Mechanism: regulates intrinsic resistance
Validation Method: complementation experiments with a functional marR
Drug Classes: Tetracycline, Nalidixic acid, Ciprofloxacin, Multiple antibiotics, Nalidixic acid|Ciprofloxacin|Ampicillin|Kanamycin|Streptomycin|Rifampin|Tetracycline|Chloramphenicol|Trimethoprim|Sulfamethoxazole, Ampicillin|Tetracycline, Chloramphenicol, Ampicillin, Fluoroquinolones, Carbapenem, Carbapenem|Colistin, Ceftriaxone, Gatifloxacin, Tigecycline, Chloramphenicol|Ciprofloxacin, Chloramphenicol|Rifampin, Levofloxacin, Ciprofloxacin|Levofloxacin, Benzalkonium chloride|Chloramphenicol|Triclosan, AMPICILLIN/CHLORAMPHENICOL/QUINOLONE/RIFAMPIN/TETRACYCLINE, Delafloxacin, Norfloxacin, Delafloxacin|Ciprofloxacin, Tetracycline|Chloramphenicol
Organisms: Escherichia coli O157:H7, Escherichia coli, Klebsiella pneumoniae, E. coli, Escherichia spp., Shewanella oneidensis, Salmonella enterica
Geographic Location: North America
Alleles: 2
Papers: 43
Databases: Reslit
Mutations: 64

Mutations

Protein Change	Nucleotide Change	Mechanism	Organism	Resistance To	Database	Validation Status
R77L	-	single resistance variant, transcriptional regulator MarR	Escherichia coli	Multiple antibioticsAMPICILLIN/CHLORAMPHENICOL/QUINOLONE/RIFAMPIN/TETRACYCLINE	Card DatabaseReference Gene Catalog	Confirmed
V96E	-	single resistance variant, transcriptional regulator MarR	Escherichia coli	Multiple antibioticsAMPICILLIN/CHLORAMPHENICOL/QUINOLONE/RIFAMPIN/TETRACYCLINE	Card DatabaseReference Gene Catalog

Allele Variants2

Allele	Database	Papers	Drug Classes	Organisms	Countries	Years	Sequence Accession	Protein Accession
mar	Reslit	2	Tetracycline, Nalidixic acid +1	Escherichia coli O157:H7 +1	-	2004, 2012	-	-
mar R	Reslit	1	Multiple antibiotics	Escherichia coli +1	North America	2023	ERP146025	-

Papers43

1

Intrinsic mechanism decreases susceptibility of Escherichia coli O157:H7 to multiple antibiotics.

PMID 14717348 · 2004

Chloramphenicol-resistant mutants of Escherichia coli O157:H7 showed increased resistance to tetracycline, nalidixic acid, and ciprofloxacin. Mutation in the mar operon was linked to decreased susceptibility.

Gene Information

Gene Name: marR
Allele: mar
Encodes: global regulator
Source Database: Reslit
Mechanism: regulates intrinsic resistance
Confers Resistance To: TetracyclineNalidixic acidCiprofloxacin
Organisms Tested In: • Escherichia coli O157:H7
Validation Method: complementation experiments with a functional marR

2

Trade-offs between drug toxicity and benefit in the multi-antibiotic resistance system underlie optimal growth of E. coli.

PMID 22631053 · 2012

Gene Information

Gene Name: marR
Allele: mar
Encodes: regulatory protein
Source Database: Reslit
Mechanism: induction of efflux pumps
Organisms Tested In: • Escherichia coli
Validation Method: measurement of promoter activity and growth experiments

3

Impact of immigration on antibiotic resistance genes in activated sludge: A study using digital droplet PCR and amplicon sequencing

PMID 37228381 · 2023

The study reveals that immigration of influent wastewater into activated sludge leads to an increase in the abundance of over 70% of the quantified antibiotic resistance genes (ARGs). Specific ARGs such as blaTEM, blaMOX, qnrS, qnrB, mphE, dfrA, tetO, tetQ, tetE, marR, msrD, robA, qacL, blaOXA, and ereA were found to increase in abundance with immigration, indicating the impact of influent immigration on the persistence of AMR in wastewater treatment plants.

Gene Information

Gene Name: marR
Allele: mar R
Encodes: Multidrug resistance regulator
Source Database: Reslit
Mechanism: Regulation of efflux pumps
Confers Resistance To: Multiple antibiotics
Organisms Tested In: • Escherichia coli
• Klebsiella pneumoniae
Geographic Location: North America
Validation Method: Droplet digital PCR
Sequence Accession: ERP146025