Physiological profiling of indigenous aquatic microbial communities to determine toxic effects of metals

Abstract

Abstract-Conventional bioassays for environmental assessment frequently rely on nonindigenous single species. We employed an assay in which whole environmental samples were distinguished by the ability of the native heterotrophic microbial communities to oxidize 95 different sole carbon sources generating a community-level physiological profile (CLPP). The average metabolic response (AMR) to the 95 variables defining the CLPP was used in laboratory bioassay studies with copper to construct doseresponse curves over several different periods of exposure: 1 h (acute), 1 d, 2 d, and 4 d. The acute dose-response of Snake River bacterioplankton communities measured by AMR was compared to the dose-response of Photobacterium phosphoreum (used in the Microtox test) and a proprietary mixed consortia (used in the Polytox test). In laboratory bioassay studies, CLPP AMR exhibited acute dose-response behavior over a greater range in copper concentrations and with less variability (per dose) than Microtox and Polytox. The acute sensitivity of CLPP AMR to copper was roughly equal to Microtox and much greater than Polytox. After a longer exposure (1 d) to copper, Snake River communities became more sensitive to copper but no additional effect was observed when the exposure was increased to 2 and 4 d. Snake River communities pre-exposed to copper (1 mg/L) for 4 d prior to acute dose-response experiments showed no difference in AMR with respect to doses up to 10 mg/L, indicating the ability of the assay to detect adaptation. Several metal-contaminated streams in Idaho were used to field validate the CLPP approach for detecting impacts of metals in the environment. The response profiles of the bacterioplankton from two downstream sites receiving metal laden mine drainage were compared to those from reference sites upstream and further downstream of the location receiving the mine drainage. The AMR of the communities at the stream reference sites were greater than sites just below the mines. We ascribed this finding to acute physiological insult near the mines and subsequent recovery downstream. Multivariate analysis revealed differences in the pattern of carbon source utilization between chronically stressed (mine waters) and unstressed communities (reference stream sites). At the third site, treatment of mine drainage by an artificial wetland was assessed above and below the wetland; water exiting the treatment wetland had a higher AMR than water that was untreated. The CLPP approach has sufficient sensitivity to detect acute contaminant impact on physiological processes of the indigenous microbial community while providing data for evaluation of chronic stress-induced adaptations in microbial community structure.

Comparative Effects of a Genetically Engineered Insect Virus and a Growth-Regulating Insecticide on Microbial Communities in Aquatic Microcosms

“…Moreover, the degree of substrate utilization does not necessarily re#ect community composition because there is often little correlation between substrate oxidation and the number of species present in a cell that are capable of using that substrate (Haack et al, 1995). Despite these constraints, metabolic pro"les from carbon source utilization patterns in Biolog plates have been successful in distinguishing microbial communities of model systems (Haack et al, 1995), rhizosphere communities from di!erent plant species (Garland, 1996), and microbial communities of wastewater treatment systems (Victorio et al, 1996), and in detecting toxic e!ects of metals on freshwater microbial communities (Lehman et al, 1997). In the present study, e!orts were made to reduce some of these confounding in#uences.…”

“…This approach is becoming widely used for classifying microbial communities of environmental samples (e.g., Lehman et al, 1997;Gamo and Shoji, 1999), but has been criticized for inaccuracies in output interpretation (Haack et al, 1995) and in characterizing microbial diversity (Konopka et al, 1998). The use of Biolog plates in these experiments was intended to provide a measure of community metabolic pro"les for comparison among microcosms over time.…”

Comparison of different microbial bioassays to assess metal‐contaminated soils

“…Per unit soluble Zn or Cu, a greater reduction in biomass occurred at day 818 than at day 11, indicating that the mode of toxicity induced by the metals is cumulative, not immediate. 24,2005 S. Tandy et al a valuable comparative tool, as long as its limitations are understood and considered carefully [35,36]. Therefore the population size gradually decreases in the presence of metal contamination, as cells die and less new cells are produced to replace them.…”

Impact of molecular surface characteristics on the reversed-phase retention behaviour of synthetic dyes

“…Synthetic dyes are extensively used in many modern industrial processes (Kross et al, 1996;Morgan-Sagastume et al, 1997); and research (Lehman et al, 1997;Cook and Linden, 1997). Due to their widespread application they can cause serious environmental pollution, accumulating in wastewaters (Petek and Glavic, 1996) and in the muscle tissues of edible fish (Plakas et al, 1996;Turnipseed et al, 1997).…”