Bacteroidetes

Bacteroides fragilis in the Gram stain

The Bacteroidetes constitute a separate tribe within the domain of the bacteria. In this phylum there is a wide variety of metabolism, ecology and morphology.

Appearance

The Gram test is negative. The cells of most species are rod-shaped and non-spore forming. There are aerobic, that is in need of oxygen, such as anaerobic representatives present. Several species, such as of the class of Flavobacteria and Cytophagen, are motile by gliding movements (moving).

Pathogenicity

Within the Bacteroidetes some pathogenic for animals and humans ( pathogenic ) species are present. In the family Flavobacteriaceae are, inter alia, some species pathogenic for birds. Capnocytophaga is part of the normal bacterial flora of humans, but may also act pathogenic under certain circumstances. Bacteroides fragilis and Bacteroides thetaiotaomicron are also opportunistic pathogens of humans. For example, fish are Types of pathogenic Cytophaga.

System

The Department Bacteroidetes contains four classes that Bacteroidia, Cytophagia, Flavobacteriia and Sphingobacteria due to 16 rRNA gene sequences. The assignment of the genera Marinifilum, Prolixibacter and Toxothrix is still under discussion. The systematics in detail:

• Class Bacteroidia order Bacteroidales Family Bacteroidaceae
• Family Marinilabiliaceae
• Family Porphyromonadaceae
• Family Prevotellaceae
• Family Rikenellaceae

• Order Cytophagales Family Catalimonadaceae
• Family Cyclobacteriaceae
• Family Cytophagaceae
• Family Flammeovirgaceae
• Family Mooreiaceae
• Family Rhodothermaceae

• Order Flavobacteriales Family Blattabacteriaceae
• Family Cryomorphaceae
• Family Flavobacteriaceae

• Order Sphingobacteriales Family Chitinophagaceae
• Family Flexibacteraceae
• Family Saprospiraceae
• Family Sphingobacteriaceae

Ecology

There are aerobic ( need of oxygen ) and anaerobic representatives present. Some are pathogenic. Among the anaerobic Bacteroideten one example the genus Bacteroides, which are the most common with 1011 cells per gram of bacteria in the human intestine. The class of Flavobacteriia contains some commensals and opportunistic pathogenic bacteria. The species are found in different habitats, eg in soil, fresh water and sea water, within different species of fish, amphibians, insects, molluscs ( mollusks ), Crustacea (crustaceans ) and in plants. Types of Blattabacterium (Family Blattabacteriaceae ) were found in termites and cockroaches. The members of the class Sphingobacteria colonize a wide range of habitats, such as Soil, groundwater, fresh water and sea water. Also, some psychrophilic ( cold-loving ) species are present, such as Flavobacterium psychrophilum and Psychrobacter. Both genera belong to the family Flavobacteriaceae.