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Bacteroides fragilis in the Gram specimen

Bacteroides fragilis in the Gram specimen

Classification : Creature
Domain : Bacteria (bacteria)
Department : Bacteroidetes
Scientific name
War 2012

The Bacteroidetes form their own strain within the domain of the bacteria . A wide variety of metabolism , ecology, and morphology are found in this phylum .


The gram test is negative. The cells of most species are rod-shaped and do not form spores. There are aerobic , i.e. oxygen-dependent, as well as anaerobic representatives. Several types, such as B. from the class of the flavobacteria and cytophages , are motile by sliding movements .


Within the Bacteroidetes there are also some pathogenic species for animals and humans . The Flavobacteriaceae family includes: a. some species pathogenic to birds. Capnocytophaga belongs to the normal bacterial flora of humans, but can also have a pathogenic effect under certain circumstances. Also Bacteroides fragilis and Bacteroides thetaiotaomicron are opportunistic pathogens of humans. For fish are z. B. Species of Cytophaga pathogenic.


The department includes bacteroidetes due to 16s rRNA - gene sequences of four classes that Bacteroidia , Cytophagia , Flavobacteriia and Sphingobacteria . The system in detail:

The genera Marinifilum and Toxothrix are currently (March 18, 2017) not assigned to any class.


There are aerobic (oxygen-dependent) as well as anaerobic representatives. Some are pathogenic. The anaerobic bacteroidete z. B. the genus Bacteroides , which are the most common bacteria in the human intestine with 10 11 cells per gram. The class of Flavobacteriia includes some commensal and opportunistic pathogenic bacteria. The species can be found in different habitats , e.g. B. in soil, fresh water and sea water, within different species of fish , amphibians , insects , molluscs , crustaceans and in plants. Types of Blattabacterium (Family Blattabacteriaceae ) were termites and cockroaches found. The members of the class Sphingobacteria colonize a wide range of habitats, e.g. B. Soils, groundwater, freshwater and seawater. Some psychrophilic (cold-loving) species are also present, such as B. Flavobacterium psychrophilum and Psychroflexus . Both genera belong to the Flavobacteriaceae family .

Individual evidence

  1. Systematics according to JP Euzéby: List of Prokaryotic names with Standing in Nomenclature (LPSN) (as of September 22, 2018)
  2. Katharina Munk (ed.): Pocket textbook Biology: Microbiology . Thieme Verlag, Stuttgart 2008, ISBN 978-3-13-144861-3


Web links

Commons : Bacteroidetes  - collection of images, videos and audio files