Antibiotics: Mode of Action

Antibiotic Molecular Weight (g/mol) Bactericidal or Bacteriostatic Mode of Action How resistance is conferred Additional Notes
Actinomycin C1 (Actinomycin D) 1255.4 Bactericidal Inhibits synthesis of RNA by binding to double-stranded DNA. It cleaves single-stranded DNA. It can be used in E.coli, yeast and mammalian cell culture. Sensitive to light.
Ampicillin 349.4 Bactericidal Inhibits cell-wall synthesis by interfering with peptidoglycan cross-linking Resistance conferred by product of TEM-1 β-lactamase (bla) gene from Tn3 (Size: 861bp). Sometimes see listed as Amp or AmpR Prone to background (due to secretion of extracellular lactamase) which results in satellite colonies. Carbenicillin is a more stable alternative.
Apramycin 539.7 Bactericidal Broad spectrum antibiotic with unique mechanism, which is based on blocking translocation and its ability to bind also to the eukaryotic decoding site. Resistance conferred by product of aminoglycoside acetyl transferase (aacC4) gene. The aacC4 gene also confers resistance to gentamycin, kanamycin and tetracycline.
Blasticidin 422.4 Bactericidal Blasticidin is a nucleoside antibiotic produced by Streptomyces griseochromogenes. It is a potent translational inhibitor in both prokaryotic and eukaryotic cells. Resistance to blasticidin is conferred by the product of the blasticidin-S deaminase (bsd) gene from Aspergillus terreus. (Size: 399bp). Optimal selection in low salt LB (LB Lennox).
Bleomycin 1415.5 Bactericidal Bleomycin is a glycopeptide antibiotic produced by Streptomyces verticillus. It causes cell death by intercalating into DNA inducing double strand breaks. It is also an effective chemotherapeutic agent. Resistance conferred by one of three ble genes from Streptomyces Also confers resistance to kanamycinand neomycin. The Sh ble gene is not suitable as positive selectable marker accompanying rpsL (streptomycin). Due to ds DNA breaks, bleomycin can interfere with cloning and intermolecular recombination.
Carbenicillin (disodium salt) 422.4 Bactericidal Carbenicillin is a semi-synthetic penicillin antibiotic that interferes with cell wall synthesis of gram-negative bacteria while displaying low toxicity to plant tissues. Carbenicillin is used as a selection in transformed Agrobacterium and E. coli. Resistance conferred by product of TEM-1 β-lactamase (bla) gene from Tn3 (Size: 861bp). Sometimes see listed as Amp or AmpR. Common alternative to ampicillin. Does not form satellite colonies.
CloNat 1359.47 not known CloNat, formally known as Nourseothricin (or NAT) is a broad-spectrum antibiotic that can be used to select for gram-positive and gram-negative bacteria, mammalian cells, yeast, filamentous fungi, protozoa, and plants,  no cross reactivity to aminoglycosidic antibiotics. Resistance conferred by nourseothricin acetyltransferase (nat1 or sat1) gene from Streptomyces noursei (Size: 573bp). Low or no background: Resistance protein is localized intracellularly and cannot be degraded in cell culture medium. In bacteria, optimal selection in low salt LB (LB Lennox).
Chloramphenicol 323.1 Bacteriostatic Inhibits translation by blocking peptidyl transferase on the 50S ribosomal subunit; at higher concentrations can inhibit eukaryotic DNA synthesis Resistance conferred by the product of the chloramphenicol acetyl transferase (cat) gene from Tn9 (Size: 660bp). Sometimes see referred to as Cam or CamR. Sensitive to light.  Optiaml solvent is ethanol.
Geneticin (G418 geneticin disulfate) 692.7 Bactericidal 418 (Geneticin) is an aminoglycoside antibiotic similar in structure to gentamicin B. This aminoglycoside is toxic to a broad range of cell types (bacterial, plant, yeast, mammalian, protozoan). Resistance to G418 is conferred by the neo gene from Tn5 encoding an aminoglycoside 3′-phosphotransferase, APT 3′ II.  G418 is commonly used in laboratory research to select genetically engineered cells (typically using the kanMX selectable marker).
Gentamicin (or Gentamycin) 477.6 Bactericidal Inhibits protein synthesis by binding to L6 protein of the 50S ribosomal subunit Resistance conferred by product of gentamycin acetyltransferase and kanamycin phosphotransferase (aacA-aphD) gene from Tn4001 (Size: 1440bp ), or  by the product of gentamycin acetyltransferase (aacC1)gene from pJN105 (Size: 534bp). aacC1 confers resistance to gentamycin only. aacA-aphD confers resistance to gentamycin and kanamycin in two separate domains. Gentamycin is heat-stabile.
Hygromycin B 527.5 Bactericidal Inhibits protein synthesis Resistance conferred by the product of the hygromycin phosphotransferase (hphB) gene from Streptomyces hygroscopicus (Size: 1323bp). Protect stock solutions from light. Store stock at 4C. Optimal selection in low salt LB (LB Lennox).
Kanamycin monosulfate 582.6 Bactericidal Broad-spectrum antibiotic; binds to 70S ribosomal subunit and inhibits growth of gram-positive and gram-negative bacteria and mycoplasma Resistance conferred by the product of the kanamycin phosphotransferase (aph ) gene from Tn903. size: 795bp, or kanamycin and neomycin phosphotransferase II (ntpII) from Tn5 (size: 805bp). Use geneticin (G418) to select in mammalian cell culture
Methotrexate 454.5 neither A folic acid analog; a powerful inhibitor of dihydrofolate reductase (DHFR). Non antibiotic used as effective antimicrobial against Staphylococcus aureus
Nalidixic Acid 232.2 Bacteriostatic; Bactericidal at higher concentrations A synthetic quinilone, it inhibits bacterial DNA gyrase-dependent processes such as DNA polymerization and supercoiling. A broad-spectrum antibiotic active against both gram-negative and gram-positive bacteria Resistance can be conferred by the product of the gyrA (nalA)gene from E. coli (Size: 2628bp).
Neomycin B sulfate 908.9 Bactericidal Binds to 30S ribosomal subunit and inhibits bacterial protein synthesis See G418-this is the same gene Confers resistance to G418 and kanmycin. Neomycin B is used for bacterial selection.
Penicillin G sodium salt 356.4 Bactericidal Inhibits peptidoglycan synthesis in bacterial cell walls
Puromycin dihydrochloride 544.4 Bactericidal Inhibits protein synthesis by acting as an analog of amino-acyl tRNA (causes premature chain termination) Puromycin N-acetyltransferase (PAC) from Streptomyces alboninger (size: 600bp). Optimal selection in low salt LB (LB Lennox).
Rifampicin 823.0 Bactericidal Strongly inhibits prokaryotic RNA polymerase and to a lesser degree mammalian RNA polymerase. Enterobacteriaceae, Acinetobacter and Pseudomonas species are resistant to rifampicin. Rifampicin is antagonistic to gentamycin
Spectinomycin 332.4 Bacteriostatic Spectinomycin is an aminocyclitol antibiotic, closely related to the aminoglycosides. Spectinomycin binds to the 30S subunit of the bacterial ribosome and interrupts protein synthesis. Streptomycin/spectinomycin adenylyltransferase (aadA) from Enterococcus faecalis (Size: 675bp). Spectinomycin resistance conferred in plant cells that contain the selectable marker gene Spcr. Spectinomycin is no longer
Streptomycin sulfate 1457.4 Bacteriostatic; Bactericidal at higher concentrations Streptomycin was the first of aminoglycosides. It inhibits protein synthesis; binds to 30S ribosomal subunit. A broad-spectrum antibiotic that works against gram-negative and gram-positive bacteria. Streptomycin is used in combination with penicillin in mammalian cell culture to prevent bacterial infection. Resistance conferred by product ofrspL gene from E. coli.
Tetracycline HCl 480.9 Bacteriostatic Inhibits bacterial protein synthesis; blocks ribosomal binding of aminoacyl-tRNA Resistance conferred by tetracycline efflux protein (tetA) from RP1, RP4 or Tn1721 (size: 1200bp), or tetracycline efflux protein (tetC) from pSC101 or pBR322 (size: 1191bp).Note: tetA gene conveys stronger resistance than that from tetC. Sensitive to light Optiaml solvent is thanol. Magnesium ions are tetracycline antagonists. Use media without magnesium salts for selection.
Trimethoprim 290.3 Bacteriostatic Trimethoprim binds to dihydrofolate reductase and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the folate synthesis pathway and interference inhibits bacterial DNA synthesis. Trimethoprim and sulfamethoxazole used in combination have synergistic effects. Haemophilus influenzae, E.coli and Klebsiella pneumoniae are susceptible to trimethoprim, while Proteus spps are resistant. Resistance conferred by product of type II dihydrofolate reductase (DHFR) from Pseudomonas aeruginosa (size 237bp).
Zeocin (Phleomycin D1) 1525 Bactericidal Broad-spectrum antibiotic that is effective against most bacteria, filamentous fungi, yeast, plant and eukaryotic cells. It is derived from a phleomycin from Streptomyces and is a member of the bleomycin family Zeocin intercalates into DNA and causes double strand breaks. Resistance conferred by the product of the Sh ble gene (375bp in size).The Sh ble gene product binds the antibiotic in a one to one ratio so it can no longer cause cleavage of DNA Optimal selection in low salt LB (LB Lennox). Zeocin is light sensitive. Due to ds DNA breaks, zeocin can interfere with cloning and intermolecular recombination. The Sh ble gene is not suitable as positive selectable marker accompanying rpsL (streptomycin)