Final answer:
The genus Mycobacterium belongs to the taxonomic class Actinobacteria, which encompasses high G+C gram-positive bacteria.
Step-by-step explanation:
The taxonomic class to which the Mycobacterium genus belong is Actinobacteria. Actinobacteria is a class of high G+C gram-positive bacteria, which includes multiple genera such as Actinomyces, Arthrobacter, and Mycobacterium, among others. This group is characterized by the high content of guanine and cytosine nucleotides in their genome, and some members of this class are known to be important in the decomposition of organic wastes, with some like Mycobacterium being significant as human or animal pathogens.