Is Mycobacterium plei gram positive or gram negative or not either or?

The correct answer is they show weak positive gram staining reaction.

Explanation:

Mycobacterium phlei is a rod-shaped species of the genus Mycobacterium. They are acid-fast bacteria with mycolic acids rich cell wall due to which gram stain cannot penetrate easily and show light purple color while staining.

When gram staining is performed on the M. phlei, they take light purple color which indicates that it is a gram-positive bacteria and is related to Actinobacteria phylum of the gram-positive bacteria.

Thus, M. phlei is a gram-positive bacteria.