Name: chlamydiae life cycle and host infection
Uploaded: 2025-08-01T06:53:04.000Z
Duration: 1 min 29 s
Channel: JoVE

Der Stamm Chlamydiae besteht aus einer einzigen Ordnung, den Chlamydiales. Typischerweise handelt es sich bei diesen Spezies um kleine Kokken mit einem Durchmesser von etwa 0,5 μm, mit einem einzigartigen Entwicklungszyklus und reduzierten Genomen mit Größen von 0,55 bis 1 Mbp.Alle Chlamydien-Spezies sind obligate intrazelluläre Parasiten verschiedener eukaryotischer Wirte wie freilebender Amöben und des Menschen. Die am besten untersuchten humanpathogenen Krankheitserreger befinden sich in den Gattungen Chlamydien und Chlamydophila. Chlamydia trachomatis verursacht Trachom – eine der Hauptursachen für Erblindung und verschiedene sexuell übertragbare Infektionen. Chlamydophila pneumoniae wird mit Atemwegserkrankungen in Verbindung gebracht, während Chlamydophila psittaci der Erreger der Krankheit Psittakose ist. Arten von Chlamydien haben einen einzigartigen Lebenszyklus, der zwei Zelltypen umfasst. Die Elementarkörper sind sich nicht vermehrende, kleine, dichte Zellen, die auf die infektiöse Übertragung spezialisiert sind. Nach der Phagozytose von Elementarkörpern durch Wirtszellen wandeln sie sich in netzartige Körper um und vermehren sich innerhalb der Wirtszellen. Als nächstes gehen netzartige Körper in Elementarkörper über. Sie werden beim Zerfall der Wirtszelle freigesetzt, infizieren benachbarte Zellen und setzen den Lebenszyklus fort.

bakterien phylum chlamydia

Bacterial Phylum Chlamydiae

Der Stamm Chlamydiae oder Chlamydiota besteht aus einer einzigen Ordnung, den Chlamydiales. Dieser Stamm umfasst ausschlie&#223;lich obligat intrazellul&#228;re Parasiten, die eukaryotische Wirte infizieren. W&#228;hrend menschliche Pathogene dieser Gruppe intensiv untersucht wurden, umfasst der Stamm zahlreiche Arten, die mit verschiedenen eukaryotischen Organismen interagieren k&#246;nnen. Mitglieder der Chlamydiae sind typischerweise kleine Kokken mit einem Durchmesser von etwa 0,5&#8239;&#956;m und zeigen einen charakteristischen Entwicklungszyklus. Wie bei vielen obligaten Parasiten und Symbionten sind ihre Genome verkleinert und reichen von 0,55 bis 1 Mbp.
Arten dieses Stammes sind hochspezialisiert auf das Eindringen in eukaryotische Zellen und deren Kolonisierung, wobei verschiedene Spezies eine Vielzahl von Wirten befallen. Parachlamydia acanthamoebae beispielsweise infiziert freilebende Am&#246;ben, insbesondere aus der Gattung Acanthamoeba. W&#228;hrend der Infektion der Am&#246;ben durchl&#228;uft Parachlamydia den typischen Entwicklungszyklus, der auch bei anderen chlamydialen Arten beobachtet wird. Viele Chlamydiae k&#246;nnen sich innerhalb freilebender Am&#246;ben vermehren oder dort persistieren, was darauf hinweist, dass diese Wirte eine bedeutende Rolle f&#252;r das &#220;berleben und die Verbreitung von Chlamydiae in nat&#252;rlichen Umgebungen spielen. Analysen der 16S-rRNA-Gensequenzen zeigen eine hohe Diversit&#228;t von Chlamydiae in der Umwelt, was auf ihre weite Verbreitung und das m&#246;gliche Vorhandensein zahlreicher unbekannter nat&#252;rlicher Wirte hindeutet. Obwohl P. acanthamoebae nat&#252;rlicherweise Am&#246;ben infiziert, kann es auch Menschen befallen &#8211; wenn auch weniger effizient als auf den Menschen spezialisierte Arten.
Die am besten untersuchten humanpathogenen Vertreter finden sich in den Gattungen Chlamydia und Chlamydophila. Dazu geh&#246;ren Arten wie Chlamydophila psittaci, der Erreger der Psittakose, Chlamydia trachomatis, verantwortlich f&#252;r Trachom und andere Erkrankungen beim Menschen, sowie Chlamydophila pneumoniae, assoziiert mit bestimmten Atemwegserkrankungen. Psittakose ist prim&#228;r eine Vogel-Epidemie, die gelegentlich auf den Menschen &#252;bergeht und grippe&#228;hnliche oder pneumonie&#228;hnliche Symptome verursacht. Trachom, eine schwere Augenerkrankung, die durch Hornhautvaskularisation und -vernarbung gekennzeichnet ist, stellt eine der weltweit h&#228;ufigsten Ursachen f&#252;r Erblindung dar. Andere St&#228;mme von C. trachomatis infizieren den Urogenitaltrakt und geh&#246;ren zu den am weitesten verbreiteten sexuell &#252;bertragbaren Infektionen.
Chlamydiae z&#228;hlen zu den biochemisch am st&#228;rksten eingeschr&#228;nkten bekannten Bakterien, mit Genomen von etwa 1 Mbp. Ihre biosynthetischen F&#228;higkeiten sind sogar begrenzter als die der Rickettsien, einer weiteren Gruppe obligat intrazellul&#228;rer Parasiten. Bemerkenswerterweise fehlt dem Genom von C. trachomatis das Gen f&#252;r FtsZ &#8211; ein Protein, das in den meisten Prokaryoten als essenziell f&#252;r die Septumbildung w&#228;hrend der Zellteilung gilt. Dar&#252;ber hinaus scheinen bestimmte Gene in C. trachomatis durch horizontalen Gentransfer von eukaryotischen Wirten &#252;bernommen worden zu sein, was m&#246;glicherweise ihre F&#228;higkeit verbessert, innerhalb von Wirtszellen zu &#252;berleben und sich zu vermehren.
Der evolution&#228;re Erfolg der Chlamydiae beruht auf ihrer effizienten &#220;berlebensstrategie, die darin besteht, Wirtsressourcen auszunutzen und resistente Zellformen f&#252;r die &#220;bertragung zu produzieren. Der chlamydiale Lebenszyklus umfasst zwei verschiedene Zellformen: (1) Elementark&#246;rperchen, die klein, dicht und auf die infekti&#246;se &#220;bertragung spezialisiert sind, und (2) Retikulark&#246;rperchen, die gr&#246;&#223;er, weniger dicht und f&#252;r die Replikation zust&#228;ndig sind. Elementark&#246;rperchen sind widerstandsf&#228;hig gegen&#252;ber Austrocknung und erm&#246;glichen eine luft&#252;bertragene Ausbreitung, was sie zu besonders effektiven Erregern des Atemtrakts macht. Im Gegensatz dazu sind Retikulark&#246;rperchen nicht infekti&#246;s und vermehren sich innerhalb der Wirtszellen durch Zweiteilung, wobei sie eine betr&#228;chtliche Inokulumsmenge f&#252;r nachfolgende Infektionen erzeugen.
Retikulark&#246;rperchen differenzieren sich nach mehreren Zellteilungen zu Elementark&#246;rperchen, die bei der Lyse der Wirtszelle freigesetzt werden. Diese Elementark&#246;rperchen infizieren dann benachbarte Zellen und setzen den Zyklus fort. Es wurde beobachtet, dass sich Retikulark&#246;rperchen mit Generationszeiten von 2&#8211;3 Stunden teilen &#8211; deutlich schneller als Rickettsien. Im Gegensatz zu Rickettsien werden Chlamydien jedoch nicht durch Arthropoden &#252;bertragen, sondern verbreiten sich prim&#228;r &#252;ber die Luft.

Bakterien Phylum Chlamydia

Der Stamm Chlamydiae oder Chlamydiota besteht aus einer einzigen Ordnung, den Chlamydiales. Dieser Stamm umfasst ausschlie&#223;lich obligat ...

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chlamydiae life cycle and host infection

Chlamydiae are bacteria that live inside eukaryotic host cells. The phylum Chlamydiae, also called Chlamydiota, contains a single order, Chlamydiales. These bacteria are obligate intracellular parasites, which means they must enter host cells to survive and grow.

Members of this group are usually very small cocci, about 0.5 μm across. They also have reduced genomes, usually between 0.55 and 1 Mbp. This limited genome fits their highly specialized way of life and their dependence on host resources. Many species infect a wide range of eukaryotic organisms, not just humans.

Some Chlamydiae infect free-living amoebae, especially Acanthamoeba. Parachlamydia acanthamoebae is one example, and it follows the same developmental cycle seen in other chlamydial species during amoeba infection. Amoebae may help Chlamydiae survive and spread in natural environments, because many species can multiply or persist inside these hosts. 16S rRNA gene studies also show that Chlamydiae are very diverse in the environment, which suggests that many natural hosts are still undiscovered.

Human pathogens in this phylum are best known from the genera Chlamydia and Chlamydophila. Chlamydophila psittaci causes psittacosis, which is mainly an avian disease that can spread to humans and cause pneumonia-like symptoms. Chlamydia trachomatis causes trachoma and other human diseases, and some strains infect the genitourinary tract and are among the most common sexually transmitted infections. Chlamydophila pneumoniae is linked to certain respiratory conditions.

Chlamydiae are also known for their highly limited biochemistry. Their genomes are around 1 Mbp, and their biosynthetic abilities are even more restricted than those of rickettsias. The genome of C. trachomatis also lacks the gene for FtsZ, a protein that most prokaryotes use for septum formation during cell division. Some genes in C. trachomatis appear to have come from eukaryotic hosts through horizontal gene transfer, which may help the bacteria survive and multiply inside cells.

Their life cycle has two main forms. Elementary bodies are small, dense, and built for infection and transmission. They are resistant to drying, which helps airborne spread and makes them effective invaders of the respiratory system. Reticulate bodies are larger, less dense, and non-infectious. They multiply inside host cells by binary fission, with generation times of about 2 to 3 hours, which is faster than in rickettsias.

After several rounds of division, reticulate bodies change into elementary bodies. The host cell then breaks apart and releases them, allowing nearby cells to be infected and the cycle to continue. Unlike rickettsias, chlamydias are not spread by arthropods. They rely mainly on airborne dispersal.

Chlamydiae Life Cycle and Host Infection

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key terms and concepts

Learn how Chlamydiae infect host cells, switch between elementary and reticulate bodies, and cause diseases like trachoma, psittacosis, and STIs.

Chlamydiae Life Cycle and Host Infection | 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

Chlamydiae Life Cycle and Host Infection

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