IN-SITU MICROBIAL ECOLOGY FOR QUANTITATIVE APPRAISAL, MONITORING, ANDRISK ASSESSMENT OF POLLUTION REMEDIATION IN SOILS, THE SUBSURFACE, THE RHIZOSPHERE AND IN BIOFILMS

Numerous studies have established a relationship between soil, sedimen t, surface biofilm and subsurface contaminant pollution and a marked i mpact on the in situ microbial community in both microcosms and in the field. The impact of pollution on the in situ microbial community can now be quantitatively measured by molecular 'fingerprinting' using 's ignature' biomarkers. Such molecular fingerprinting methods can replac e classical microbiological techniques that relied on isolation and su bsequent growth of specific microbes from the in situ microbial commun ity. Classical methods often revealed less than 1% of the extant micro bial communities. Molecular fingerprinting provides a quantitative mea sure of the in situ viable microbial biomass, community composition, n utritional status, relative frequency of specific functional genes, nu cleic acid polymers of specific microbes, and, in some cases, the comm unity metabolic activity can be inferred. Current research is directed at establishing correlations between contaminant disappearance, dimin ution in toxicity, and the return of the viable biomass, community com position, nutritional status, gene patterns of the in situ microbial c ommunity towards that of the uncontaminated soil, sediment or subsurfa ce material with the original uncontaminated microniche environments. Compared to the current reliance on disappearance of pollutants and as sociated potentially toxic products for detection of effective and qua ntitative bioremediation, assessment of the in situ microbial communit y will be an additional and possibly more convincing risk assessment t ool. The living community tends to accumulate and replicate toxic insu lts through multiple interactions within the community, which may then effect viable biomass, community composition, nutritional status, com munity metabolic activities, and specific nucleic acid polymer pattern s. (C) 1998 Elsevier Science B.V.