Question

All of the following are classes of the proteobacteria except

A) sigma
B) beta
C) alpha
D) delta
E) epsilon

Answer 1

Sigma (Option A) is not a class of the proteobacteria; the recognized classes include Alpha, Beta, Gamma, Delta, and Epsilon, with Epsilonproteobacteria containing human pathogens like Campylobacter and Helicobacter.

Step-by-step explanation:

The classes of the proteobacteria include alpha, beta, gamma, delta, and epsilon. Among the choices listed in the question, sigma is not a recognized class within the phylum Proteobacteria. The Epsilonproteobacteria class is noted for containing important human pathogens, such as those from the genera Campylobacter and Helicobacter. The Betaproteobacteria class does not include Campylobacter, which is actually part of the Epsilon class.