The Negativicutes is a class of firmicute bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, whose members have a peculiar cell wall composition which stains Gram negative, unlike most other members of the Firmicutes. The family Veillonellaceae, formerly known as Acidaminococcaceae, we once considered members of the clsss Clostridia

Clostridia

The Clostridia are a class of Firmicutes, including Clostridium and other similar genera. They are distinguished from the Bacilli by lacking aerobic respiration. They are obligate anaerobes and oxygen is toxic to them. Species of the genus Clostridium are all Gram-positive and have the ability to...

. The name Selenobacteria also refers to some members of this group. The description of this family was emended

Bacterial taxonomy

Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.In the scientific classification established by Carl von Linné, each species has to be assigned to a genus , which in turn is a lower level of a hierarchy of ranks .In the currently accepted classification...

 in 2010 and, together with the Acidaminococcaceae (familia nova

Bacterial taxonomy

Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.In the scientific classification established by Carl von Linné, each species has to be assigned to a genus , which in turn is a lower level of a hierarchy of ranks .In the currently accepted classification...

, which means a newly coined taxa), it was placed in the order Selenomonadales (ordo novus) in the class Negativicutes

Negativicutes

The Negativicutes is a class of firmicute bacteria, whose members have a peculiar cell wall composition which stains Gram negative, unlike most other members of the Firmicutes. The family Veillonellaceae, formerly known as Acidaminococcaceae, we once considered members of the clsss Clostridia. The...

 (classis novus) of the phylum Firmicutes.

Members of this family are all obligate anaerobes, and occur in habitats such as rivers, lakes, and the intestines of vertebrates. They range from spherical forms, such as Megasphaera and Veillonella

Veillonella

Veillonella are gram-negative anaerobic cocci. This bacterium is well known for its lactate fermenting abilities. They are a normal bacterium in the intestines and oral mucosa of mammals...

, to curved rods, as typified by the Selenomonad

Selenomonad

The genus Selenomonas constitutes a group of motile crescent-shaped bacteria within the Veillonellaceae family and includes species living in the gastrointestinal tracts of animals, in particular, the Ruminants....

s. Selenomonas has a characteristic crescent-shape, with flagella inserted on the concave side, while Sporomusa is similar but non-motile. Their names refer to this distinctive morphology: selene

Selene

In Greek mythology, Selene was an archaic lunar deity and the daughter of the Titans Hyperion and Theia. In Roman mythology, the moon goddess is called Luna, Latin for "moon"....

means moon, and musa means banana

Banana

Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN)

and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project 
Notes:

♠ Strains found at the [National Center for Biotechnology Information] (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN)

♪ Prokaryotes where no pure (axenic) cultures are isolated or available, i. e. not cultivated or can not be sustained in culture for more than a few serial passages