The invention relates to systems and methods for production of compounds by yeast and other organisms. In one approach yeast engineered for production of a compound of commercial value is cultured together with a cellulosic bacteria, and the yeast uses a metabolic product produced by the bacteria as a carbon source. Methyl halides are an example of compounds that may be produced by this process. The invention also relates to production of organic compounds using genetically engineered organisms expressing a S-adenosylmethionine (SAM)-dependent methyl halide transferase. In one approach the organism, halides and a carbon source are incubated in a cultivation medium under conditions in which methyl halide is produced. The methyl halide may be collected and converted into non-halogenated organic molecules.