Soil microbiologists have pondered the effect that adsorption has on the biological availability of nonpolar compounds in soils, assuming the only biologically available form is dissolved in water.  Adsorption by soil organic matter, by this reasoning, renders nonpolar compounds less available for mineralization thereby prolonging the persistence of nonpolar contaminants in soils.  In a few cases, microbiologists have discovered bacterial strains capable of mineralizing nonpolar contaminants adsorbed by synthetic adsorbents raising the possibility that adsorption may not always prevent degradation.

We have discovered that a strain found capable of mineralizing biphenyl adsorbed by synthetic adsorbents is also capable of substantially mineralizing biphenyl adsorbed by colloidal soil organic matter.  Our study demonstrates certain bacteria are not confined to degrading nonpolar contaminants dissolve in the aqueous phase.

These findings led us to reconsider the conventional isolation protocol.  Conventional protocol for isolating microbes from soil capable of degrading specific organic compounds involves inoculating enrichment cultures with soil, the sole carbon and energy source in the enrichment cultures being the compound in question provided in soluble form.  This approach favors bacteria that mineralize dissolved nonpolar compounds.  We applied an alternative protocol that inoculated enrichment cultures containing phenanthrene adsorbed to colloidal organic matter.  This protocol consistently isolated bacteria with marked capacity to utilize adsorbed phenanthrene.