Microbial biomass and activities associated with subsurface environments contaminated with chlorinated hydrocarbons

Soil microcosms and enrichment cultures from subsurface sediments and groundwaters contaminated with trichloroethylene (TCE) were examined. Total lipids, I‐‘⁴C]acetate incorporation into lipids, and Me‐³H]thymidine incorporation into DNA were determined in these subsurface environments. In heavily TCE‐contam‐inated zones (greater than 500 mg/L) radioisotopes were not incorporated into lipids or DNA. Radioisotope incorporation occurred in sediments both above and below the TCE plume. Phospholipid fatty acids (PLFA) were not detected, i.e., less than 0.5 pmol/L in heavily contaminated groundwater samples. In less contaminated waters, extracted PLFA concentrations were greater than 100 pmollL and microbial isolates were readily obtained. Degradation of 30–100 mg/L TCE was observed when sediments were amended with a variety of energy sources. Microorganisms in these subsurface sediments have adapted to degrade TCE at concentrations greater than 50 mg/L.