Functional gene array-based analysis of microbial communities in heavy metals-contaminated lake sediments

Area of Science:

• Environmental microbiology
• Geochemistry
• Biogeochemistry

Background:

• Lake DePue, Illinois, has experienced over 80 years of zinc smelting contamination.
• Previous studies noted increased sulfate reduction and decreased biomass with rising metal concentrations, yet stable microbial community structure (16S rRNA).

Purpose of the Study:

• Investigate the sediment microbial community structure and functional potential in response to metal contamination.
• Identify specific microbial genes and populations affected by heavy metals in Lake DePue.

Main Methods:

• Utilized a functional gene microarray (GeoChip) to analyze over 10,000 functional genes.
• Applied nonmetric multidimensional scaling and clustering analyses to assess community structure.
• Correlated pore-water metal concentrations with the abundance of specific gene categories, including sulfate reduction (dsr) and metal resistance genes.

Main Results:

• Overall microbial community structure appeared stable, but specific gene categories differed across metal contamination gradients.
• Sulfate reduction (dsr) genes and metal resistance genes were more abundant and correlated with metal contamination.
• Zinc, cadmium, and manganese concentrations were most predictive of dsr gene presence.

Conclusions:

• Metal contamination significantly influences microbial community structure and function in Lake DePue sediments.
• Increased abundance of metal-resistant and sulfate-reducing populations contributes to microbial community resistance and stability.
• These specific microbial populations play a key role in mediating the effects of long-term metal pollution.