Streptomyces luteogriseus strain 099, producing a new type of macrolide antibiotic with anti-coxB6 virus and anti-HIV protease activities, was isolated from soil. PCR was optimized to amplify beta-ketoacyl-ACP synthase (KS) genes. The system was optimized around the use of higher concentrations of DMSO (15% vs. 10% v/v) and dNTP (500 mu M vs. 50 -200 mu M) and a lower annealing temperature (55 degrees C vs. 60 - 70 degrees C) than the normal PCR method used to amplify high GC content DNA.