Abstract
The observations made on the relationships existing between various microorganisms isolated from natural sources have been described. The species of Chaetomium were found to be antagonistic towards some other fungi. Competition among microorganisms was noticed in many instances. Mutualistic symbiosis was found to occur between a sterile strain of Thielavia setosa, which formed cleistothecia only in the presence of other fungi like Aspergillus nidulans, A. variecolor, Thielavia sepedonium, and T. terricola.
