1. 
   Photochromogen
   An organism (e.g. a Mycobacterium) forming pigment only when exposed to light.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
2. 
   photochromogen
   (fo″to-kro´mә-jәn) a microorganism whose pigmentation develops as a result of exposure to light. adj., photochromogen´ic., adj.
   Found op http://www.encyclo.co.uk/local/21001
   
   
3. 
   photochromogen
   photochromogen 1. A microorganism whose pigmentation develops as a result of exposure to light. 2. a mycobacterium that forms yellow or orange colonies when grown in the light.
   Found op http://www.wordinfo.info/words/index/info/view_unit/2803/6
   
   

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