Which Mycobacterium species is characterized by positive urease and considered a photochromogen?

Mycobacterium marinum is the species known for being urease positive and classified as a photochromogen. Urease production allows this organism to hydrolyze urea, leading to an alkaline environment which is important for its survival in certain habitats. As a photochromogen, it has the ability to produce pigments when exposed to light. In its case, the pigmentation is typically enhanced in the presence of light, distinguishing it from other Mycobacterium species.

To further clarify, Mycobacterium kansasii is also a photochromogen but does not have a consistent urease production, making it distinct from Mycobacterium marinum when considering both characteristics. Mycobacterium tuberculosis is a non-photochromogenic species and is not recognized for urease production, while the Mycobacterium avium-intracellulare complex typically demonstrates non-photochromogenic features as well and is not urease positive. Therefore, the combination of being both urease positive and a photochromogen distinctly identifies Mycobacterium marinum.