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.
Citation
Gorzelnik, Karl V (2014). Competition-Mediated Identification of the First Environmental Protein Responsible for the Degradation of the Lipopeptide Surfactin. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /152837.