A highly branched hyphal morphology was observed in early stage (high nutrient availability) batch liquid culture and high dilution rate chemostat culture of Saccharopolyspora erythraea and Streptomyces coelicolor. In contrast, nutrient exhausted batch cultures and low dilution rate chemostat cultures contained unbranched myceUa. Formation of un-branched mycelia is thought to have evolved to expedite rapid "searching" of the soil environment, in order to locate nutrients. The increased frequency of branching is assumed to provide a structure that can exploit nutrient rich micro-habitats (once located) effectively.