Biological Indicator (BI) Posted on 3rd November 201519th July 2021 by ThePD (The Project Definition) Biological Indicator (BI) is the characterised preparation of a specific microorganism show the presence of specific environmental conditions. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Business and tagged biology. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.