Table of Contents
What is Rickettsia?
Rickettsia is a genus of bacteria that contains a few dozen species, most of which are obligate intracellular parasites. These bacteria are Gram-negative and typically 0.5-1.0 micrometers in size. Rickettsiae transmitted by arthropods, most commonly ticks and fleas, and can cause a variety of diseases in humans, animals, and plants.
Classification of Rickettsia
Rickettsia are a genus of bacteria that can cause a variety of diseases in humans, including typhus, Rocky Mountain spotted fever, and Q fever.
Classification
- It is a genus of Gram-negative, obligate intracellular bacteria. The members of this genus obligate parasites of eukaryotic cells and typically transmitted by arthropods. There are currently 17 recognized species in this genus, and all of them associated with arthropod hosts.
- Rickettsia species are small, pleomorphic bacteria that are difficult to grow in vitro. They are typically coccobacilli, but can range in shape from cocci to filamentous rods. All Rickettsia species are obligately intracellular, meaning that they can only grow and replicate inside of eukaryotic cells.
- Typically transmitted by arthropods, such as ticks, fleas, and mites. Therefore these arthropods typically serve as vectors, or carriers, of the bacteria, and can transmit the bacteria to humans and other animals through their bites.
- Once inside the host, Rickettsia bacteria invade and replicate within host cells. This replication can cause host cell death, and can lead to the development of disease symptoms in the host.
- Rickettsia are classified as Gram-negative bacteria, meaning that they stain pink when stained with Gram stain. They are also classified as obligate intracellular bacteria, meaning that they require eukaryotic cells in order to grow and replicate.
Rickettsia Characteristics
Rickettsia are a highly diverse group of obligate intracellular bacteria that are related to the proteobacteria. They are gram-negative, and many are rod-shape. However they highly adapted to life inside other cells, where they reproduce asexually. Rickettsia are spread by arthropods, particularly ticks and fleas, and can cause a variety of diseases in humans, including typhus, Rocky Mountain spotted fever, and Q fever.
Genomics
- Genomics has allowed us to sequence genomes, to identify the genes in genomes, and also to study the function of genes.
- The Human Genome Project was an international project that aimed to sequence the human genome. The project completed in 2003, and the complete human genome sequence published in 2004. The project revealed that the human genome contains approximately 20,000-25,000 genes.
