The Selenomonadales are the only order of bacteria within the class Negativicutes; unlike most other members of Firmicutes, they are Gram-negative. The phylogeny of this order was determined by 16S rRNA comparisons. Samples of bacterial strains within this order have been isolated from the root canals of healthy human teeth.

The Selenomonadales are the only order of bacteria within the class Negativicutes; unlike most other members of Firmicutes, they are Gram-negative. The phylogeny of this order was determined by 16S rRNA comparisons. Samples of bacterial strains within this order have been isolated from the root canals of healthy human teeth.