Competition-Mediated Identification of the First Environmental Protein Responsible for the Degradation of the Lipopeptide Surfactin

Abstract

Streptomycetes, as nonmotile microbes, are forced to adapt to environmental conditions they cannot escape. In order to adapt to their environment streptomycetes produce an array of both secondary metabolites to antagonize competitors and degradative enzymes to take advantage of various nutritional sources and to degrade xenobiotics, molecules from foreign organisms. This work shows two instances of streptomycetes adapting to their neighbors. Streptomyces sp. Mg1 was determined to be resistant to surfactin, a molecule produced by Bacillus subtilis which inhibits aerial hyphae development. After identifying possible enzymatic sources of degradation several candidate enzymes were cloned and expressed in Escherichia coli. One candidate, ‘secreted hydrolase’ was purified under denaturing conditions and refolded. This enzyme was shown to degrade surfactin and another B. subtilis metabolite, plipastatin. Upon alteration of assay conditions the enzyme was also able to degrade daptomycin. The other instance of a streptomycete adapting to its neighbors is of S. coelicolor, which in the presence of some strains of B. subtilis is able to produce undecylprodigiosin earlier than it normally would. The induction of undecylprodigiosin indicates that either B. subtilis is altering a neighbor’s physiology through a secreted compound or that S. coelicolor is able to detect a xenobiotic and responds by producing an antibiotic compound. The inducing compound from B. subtilis was fractionated and conditions for its further purification were determined.