This invention involves the co-incubation of Rhodococcus fascians with Streptomyces padanus to produce two new isomeric antibiotics, coined rhodostreptomycin A and B. The Rhodococcus fascians strain that developed the ability to produce these two new antibiotics, 307CO, was able to eliminate Streptomyces from its culture, presumably by the toxicity of rhodostreptomycin A and B. The inventors have hypothesized that Rhodococcus fascians gained the ability to produce rhodostreptomycin through a lateral gene transfer from its co-cultured Streptomyces. Genomic analysis revealed that 307CO harbored a long strand of DNA derived from Streptomyces. Furthermore, rhodostreptomycin A and B production correlated with the presence of Streptomyces-derived DNA in Rhodococcus. Rhodostreptomycin was purified by fractionation, cation exchange, and reverse-phased HLPC. NMR analysis was used to reveal the chemical formula and hydrocarbon structure of rhodostreptomycin A and B and verify their novelty. Rhodostreptomycin A and B were not shown to have any activity against eukaryotes when applied to S. Cerevisiae or human leukemia (HL-60).