Name: how antibiotics block bacterial cell walls
Uploaded: 2026-03-12T13:36:02.000Z
Duration: 1 min 23 s
Channel: JoVE

Bacterial cell walls are generally rigid and composed mainly of peptidoglycan.Structurally, peptidoglycan consists of long glycan chains cross-linked by short peptides, which form a mesh that protects the cell against osmotic pressure.Because peptidoglycan is essential for cell survival, beta-lactam antibiotics such as penicillin interfere with its synthesis in actively growing cells.These antibiotics contain a distinctive four-membered beta-lactam ring.This ring mimics the natural dipeptide D-alanyl-D-alanine, a substrate for the transpeptidase activity of penicillin-binding proteins, or PBPs.These proteins are responsible for cross-linking glycan chains in the peptidoglycan matrix.When the beta-lactam ring covalently binds to the active site of a PBP, it blocks the cross-linking reaction.As a result, the bacterial cell wall remains weak and incomplete, making the cells highly vulnerable to osmotic lysis.At the same time, autolytic enzymes such as murein hydrolases further contribute to the breakdown of the defective cell wall.

inhibitors of gram-positive cell wall synthesis

Inhibitors of Gram-positive Cell Wall Synthesis

Bacteri&#xEB;le celwanden zijn doorgaans rigide structuren die voornamelijk bestaan uit peptidoglycaan, een netwerkachtig polymeer dat mechanische stevigheid biedt en de celvorm handhaaft. De synthese van peptidoglycaan is een cruciaal proces in de bacteri&#xEB;le groei en vormt een primair aangrijpingspunt voor veel antibiotica.
Werkingsmechanisme van b&#xE8;ta-lactamantibiotica
B&#xE8;ta-lactamantibiotica, zoals penicilline, remmen de peptidoglycaansynthese in actief groeiende cellen. Deze antibiotica hebben een karakteristieke vierledige b&#xE8;ta-lactamring die structureel lijkt op het D-alanyl-D-alanine-dipeptide&#x2014;het natuurlijke substraat voor het enzym transpeptidase, ook bekend als een penicillinebindend eiwit, of PBP. Door onomkeerbaar te binden aan de actieve plaats van dit enzym voorkomen b&#xE8;ta-lactamantibiotica de dwarsverbinding van peptideketens binnen het peptidoglycaan. Deze verstoring stopt de opbouw van de celwand en activeert mure&#xEF;nehydrolasen&#x2014;enzymen die peptidoglycaan afbreken&#x2014;wat uiteindelijk leidt tot bacteri&#xEB;le cellyse.
B&#xE8;ta-lactamantibiotica worden ingedeeld in vier hoofdgroepen: penicillines, cefalosporinen, monobactams en carbapenems. Penicillines (bijv. penicilline G, ampicilline) waren de eerste ontwikkelde b&#xE8;ta-lactamantibiotica en worden voornamelijk gebruikt voor de behandeling van infecties met grampositieve bacteri&#xEB;n, hoewel veel ervan ook een uitgebreidere werkzaamheid tegen gramnegatieve bacteri&#xEB;n hebben. Cefalosporinen (bijv. cefazoline, ceftriaxon) bieden een breder werkingsspectrum en een verbeterde resistentie tegen b&#xE8;ta-lactamase-enzymen die door bacteri&#xEB;n worden geproduceerd. Monobactams (bijv. aztreonam) zijn voornamelijk actief tegen gramnegatieve bacteri&#xEB;n en zijn vooral nuttig bij pati&#xEB;nten met een penicillineallergie. Carbapenems (bijv. meropenem, imipenem) hebben het breedste spectrum van alle b&#xE8;ta-lactamantibiotica en worden doorgaans gereserveerd voor ernstige of multiresistente infecties.
Vanwege hun structurele diversiteit en brede klinische toepasbaarheid behoren b&#xE8;ta-lactamantibiotica nog steeds tot de meest gebruikte en best bestudeerde klassen van antibiotica in de moderne geneeskunde.
Werkingsmechanisme van glycopeptide-antibiotica
Glycopeptide-antibiotica, zoals vancomycine, teicoplanine en dalbavancine, werken via een mechanisme dat verschilt van dat van b&#xE8;ta-lactamantibiotica. Deze middelen binden rechtstreeks aan de D-alanyl-D-alanine-uiteinden van peptidoglycaanprecursoren en vormen stabiele complexen die de enzymatische toegang tot het substraat verhinderen. Deze binding blokkeert sterisch de activiteit van transglycosylase, het enzym dat verantwoordelijk is voor het katalyseren van de verlenging van glycaanstrengen, en van transpeptidase, dat de dwarsverbinding van peptideketens medieert. Als gevolg hiervan worden zowel de polymerisatie- als de dwarsverbindingsstappen in de biosynthese van de celwand stopgezet.
In tegenstelling tot b&#xE8;ta-lactamantibiotica remmen glycopeptiden deze enzymen niet rechtstreeks; in plaats daarvan werken ze door de doelwitplaats af te schermen. Dit indirecte mechanisme is met name gunstig tegen bacteri&#xEB;n die resistentie tegen b&#xE8;ta-lactamantibiotica hebben verworven door de productie van b&#xE8;ta-lactamasen of de modificatie van penicillinebindende eiwitten, of PBP&#x27;s. Glycopeptiden zijn het meest effectief tegen grampositieve bacteri&#xEB;n, omdat hun grote moleculaire omvang en hydrofiliciteit voorkomen dat zij het buitenmembraan van gramnegatieve bacteri&#xEB;n binnendringen.

Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains ...

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inhibitors-of-gram-positive-cell-wall-synthesis

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Microbiology

Microbiologie

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Eenheid

Antimicrobial Agents

Antimicrobiële middelen

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how antibiotics block bacterial cell walls

Bacterial cell walls are rigid structures built mainly from peptidoglycan. This mesh-like polymer gives bacteria strength and helps maintain cell shape. Because peptidoglycan synthesis is essential for growth, it is a major target for antibiotics.

Beta-lactam antibiotics, such as penicillin, stop peptidoglycan synthesis in actively growing cells. They have a four-membered beta-lactam ring that mimics the D-alanyl-D-alanine dipeptide, which is the natural substrate for transpeptidase, also called a penicillin-binding protein (PBP). By binding irreversibly to the enzyme’s active site, these drugs block cross-linking between peptide chains. That disruption halts cell wall assembly, activates murein hydrolases that break down peptidoglycan, and can lead to bacterial cell lysis.

Beta-lactams are grouped into four main classes: penicillins, cephalosporins, monobactams, and carbapenems. Penicillins, such as penicillin G and ampicillin, were the first beta-lactams developed and are mainly used for Gram-positive infections, although many now also cover Gram-negative bacteria. Cephalosporins, such as cefazolin and ceftriaxone, have broader activity and are more resistant to beta-lactamase enzymes made by bacteria.

Monobactams, such as aztreonam, act mainly against Gram-negative bacteria and are especially useful in patients with penicillin allergies. Carbapenems, such as meropenem and imipenem, have the broadest spectrum of the beta-lactams and are usually reserved for severe or multidrug-resistant infections. Because of their structural variety and clinical value, beta-lactams remain one of the most studied antibiotic groups in modern medicine.

Glycopeptide antibiotics work in a different way. Drugs such as vancomycin, teicoplanin, and dalbavancin bind directly to the D-alanyl-D-alanine ends of peptidoglycan precursors. This creates a stable complex that blocks enzyme access to the substrate and prevents both transglycosylase, which lengthens glycan strands, and transpeptidase, which makes peptide cross-links.

Unlike beta-lactams, glycopeptides do not block these enzymes directly. Instead, they shield the target site and stop both polymerization and cross-linking during cell wall biosynthesis. This indirect action can be useful against bacteria that resist beta-lactams by producing beta-lactamases or changing their PBPs. Glycopeptides work best against Gram-positive organisms because their large size and hydrophilic nature keep them from crossing the outer membrane of Gram-negative bacteria.

How Antibiotics Block Bacterial Cell Walls

how-antibiotics-block-bacterial-cell-walls

Bacterial cell walls are rigid structures built mainly from peptidoglycan. This mesh-like polymer gives bacteria strength and helps maintain cell shape. Because peptidoglycan synthesis is essential for growth, it is a major target for antibiotics. Beta-lactam antibiotics, such as penicillin, stop peptidoglycan synthesis in actively growing cells. They have a four-membered beta-lactam ring that mimics the D-alanyl-D-alanine dipeptide, which is the natural substrate for transpeptidase, also...

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key terms and concepts

Learn how beta-lactams and glycopeptides disrupt bacterial cell wall synthesis, from penicillin binding proteins to vancomycin’s action on peptidoglycan.

How Antibiotics Block Bacterial Cell Walls | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Antibiotics Block Bacterial Cell Walls

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