Proteobacteria

The Proteobacteria are a major group (phylum) of bacteria.

Alphaproteobacteria is a class of Proteobacteria; like all Proteobacteria, they are Gram-negative.

Betaproteobacteria is a class of Proteobacteria that are all Gram-negative.

The two main groups of morphologically unusual proteobacteria include spirillum and prosthecate bacteria.

Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria.

Deltaproteobacteria is a class of Proteobacteria that are Gram-negative.

Epsilonproteobacteria is a class of Proteobacteria that are Gram-negative.