 The "Betaproteobacteria" are one of the eight classes that make up the "Proteobacteria".The "Betaproteobacteria" are most closely related to the "Gammaproteobacteria", "Acidithiobacillia" and "Hydrogenophilalia", and together they make up a taxon which has previously been called ""Chromatibacteria"".Four orders of "Betaproteobacteria" are currently recognised — the "Burkholderiales", the "Neisseriales", the "Nitrosomonadales" and the "Rhodocyclales".