The class Flavobacteriia is composed of a single class of environmental bacteria. It contains the family Flavobacteriaceae, which is the largest family in the phylum Bacteroidota. This class is widely distributed in soil, fresh, and seawater habitats. The name is often spelt Flavobacteria, but was officially named Flavobacteriia in 2012.
Flavobacteriia are gram-negative aerobic rods, 2–5 μm long, 0.1–0.5 μm wide, with rounded or tapered ends. They form circular cream to orange coloured colonies on agar, and are typically simple to successfully culture. Flavobacteriia is a chemoorganotroph and are known for their ability to mineralize or degrade dissolved organic matter of high molecular weight and particulate plant material.
Flavobacteriia have impacts on both the environment and human society, as they are able to cause diseases in many organisms. They are important in the decomposition of organic matter and pollutants, and are key members in the formation of marine biofilms. They also have been known to cause diseases in some animal species, specifically bacterial cold water disease and columnaris disease.
Taxonomy
Flavobacteriia is the largest of the four classes of phylum Bacteroidota. It is a single-order class, and its largest family is Flavobacteriaceae. Flavobacteriaceae is the largest family in the phylum Bacteroidota. The family has over 90 genera and hundreds of species. The genus Flavobacterium is most commonly used in studies of Flavobacteriia. This genus has 100 classified species with many additional unclassified species. Recent taxonomic updates have reclassified several Flavobacterium species to new genera such as Microbacterium, Salegentibacter, and Planococcus. Domain Bacteria Phylum Bacteroidota Class Flavobacteriia Order Flavobacteriales Family Crocinitomicaceae Family Cryomorphaceae Family Flavobacteriaceae Genus Flavobacterium Genera Microbacterium, Salegentibacter, and Planococcus. Family Ichthyobacteriaceae Family Luteibaculaceae Family Parvicellaceae Family Salibacteraceae Family Schleiferiaceae Family Vicingaceae Family Weeksellaceae Family Flavobacteriales incertae sedis Additionally, unclassified Flavobacteriales
History
The genus Flavobacterium was established in 1889. It was first written about in 1923 in Bergey's manual of determinative bacteriology and contained one of the first of 46 discussed species. The manual defines Flavobacteriia as gram-negative, non-spore-forming, aerobic, non-gliding rods. In 1999, Flavobacteriia was discovered to have a yellow pigment in colonies. It was also identified that they move through gliding and only grow in the presence of oxygen.
In 1922, Flavobacterium columnare, an agent of columnaris disease with significant effects on fish, was discovered in the Mississippi River, making it one of the earliest known diseases of its kind. The disease was originally labelled as a Myxobacteria in 1944, but was renamed to Flavobacterium columnare in 1996 with 10 species. Flavobacteriia used to contain many non-related species of yellow, rod-shaped bacteria, but taxonomy has changed and stabilized due to the sequencing of rRNA to deduce phylogenetic relationships.
Habitat
Flavobacteriia are widely distributed with high abundances in aquatic systems. They have been found in diseased fish, microbial mats, freshwater and river sediments, seawater and marine sediments, soil, glaciers, and Antarctic lakes. Increases in abundance are found in areas of high organic substrate inputs due to their role in the uptake, degradation, and decomposition of organic matter and can result in bacterial dominance. Flavobacteriia is prominent in ocean sediments and decreases with increasing depth, and prefer sediments lacking vegetation.
These bacteria also are highly abundant in melt ponds, solid ice cores, sea ice, and brine, as well as the photic zone. More specifically, these photic zones show that Flavobacteriia are prominent in productive environments such as phytoplankton blooms and upwelling zones. Flavobacteriia are prominent members of marine biofilms. They have large impacts on the functioning of marine biofilms, however their abundance is believed to be heavily underestimated.
Flavobacteriia can also be found in non-marine systems and are most common in Asian regions, specifically Korea and China, as well as Japan and India.