SDS in liquid culture was quantified using a modification [ 151 of the methylene-blue-active-substances assay
for anionic surfactants of Hayashi [22]. SDS in soil was extracted by shaking 10 g soil with 40 ml of
distilled water for 30 min at 150 rpm and room temperature. After 5 min of settling down, 1.5 ml of the
“clear” phase was centrifuged; SDS quantification was performed in the clear supematant as described