Which Taxon is NOT Gram-Positive

Question

Which taxon is NOT gram-positive?
A) Actinobacteria
B) Firmicutes
C) Sphingobacteria
D) Streptococcus

Accepted Answer

Actinobacteria, Firmicutes, and Streptococcus are all examples of gram-positive bacteria. Sphingobacteria, however, are gram-negative bacteria.