Streptomyces development is a complex process that eventually finishes with the formation of individual unigenomic spores from the aerial hyphae. Intraspecific and interspecific signals must play a key role in triggering or blocking this process. Here we show that interaction between two types of microorganisms, Streptomyces and yeasts, leads to alteration of the Streptomyces developmental program. This alteration is due to the action of invertase produced by the yeast on the sucrose present in the culture media, making glucose and fructose readily available for growth.