Microbial models in screening of inhibitors of sterol biosynthesis

: On the base of previously developed microbial models high effective scheme for screening of inhibitors of sterol biosynthesis (ISB) is proposed. It is based on cultivation of halophilic bacteria Halobacterium salinarum (former Halobacterium halobium), possessing mevalonate pathway of sterol biosynthesis, and cultivation of fungus Acremonium fusidioides (former Fusidium coccineum), that is producer of steroid antibiotic fusidin (fusidic acid), which biosynthesis has great similarity (with coincidence of its initial steps till squalene formation) to cholesterol biosynthesis in human organism. In H. salinarum model ISB are revealed as compounds that inhibit test-culture growth, whereas in A. fusidioides test-system they are revealed as compounds that strongly reduce fusidin production without any visible influence on producer's growth. Mevalonate that is one of the crucial intermediates of sterol biosynthesis remove inhibition induced by many microbial metabolites that is the evidence of their action at early stages of sterol biosynthetic pathway, including HMG-CoA reductase step. Both test-systems are developed as micromethod and could be easily mechanized due to miniaturization of microbiological procedures, cultivation in sterile 96-well plates and usage of automatic micropipettes and dispensers. Effectiveness of both test-systems, as well as their sensitiveness, laboriousness and ability to give false-positive or false-negative results in ISB screening work is compared. The proposed scheme of screening of ISB includes microbial models at early steps of screening procedures and Hep G2 test-system at the late step. The preliminary screening of microbial metabolites possessing antifungal activity at initial step is compulsory. Miniaturization and mechanization of microbial processes and purification of producers' culture broth with micro- and ultrafiltration are under consideration as well.