We are examining the systems-level effects of multiple metal exposure in microorganisms. While many studies have explored the impacts of individual metals on bacterial physiology, multiple metals will frequently co-exist at elevated levels in contaminated sites.  Using a native Bacillus cereus isolate from a contaminated site, we have found that  metals in combination impact cell physiology in a manner that could not have been predicted from summing phenotypic responses to the individual metals. Exposure to this metal mixture induced a global iron starvation response not observed during exposure to the individual metals. Disruption of iron homeostasis decreased the activity of iron-cofactor-containing enzymes that are critical for cellular metabolism.

Moving forward, we are examining the mechanisms through which cells maintain intracellular metal homeostasis during periods of multi-metal stress either in the form of aqueous metal ions or solid metallic materials using the model microorganisms Escherichia coli and Bacillus subtilis.

This work is supported in part by the Syracuse University Center of Excellence in Environmental and Energy System Innovations. 

Model for decreased nitrate/nitrite reductase activity during mixed metal exposure. Goff, J.L. et al. Mixed heavy metal stress induces global iron starvation response. ISME J 17, 382–392 (2023). 

We are exploring how how mobile genetic elements (MGEs) shape microbial genome evolution in the ORR subsurface. Movement of MGEs by horizontal gene transfer (HGT) can promote the rapid adaptation of microorganisms to environmental stressors through analysis of both metagenome-assembled MGEs as well as MGEs in the genomes of pure culture isolates from contaminated environments.  Additionally, we are using adaptive laboratory evolution (ALE) to experimentally probe mechanisms of genome evolution during environmental stress.  In particular, we are interested in plasmid gene content and stability and the expansion of transposable elements in microbial genomes.  

Plasmids identified in the genome of an isolated representative of a dominant species in a mixed waste contaminated subsurface environment. Goff, J.L. et al. (2022) Ecophysiological and genomic analyses of a representative isolate of highly abundant Bacillus cereus strains in contaminated subsurface sediments. Environmental Microbiology, 24( 11), 5546– 5560. 

Microplastics can be vectors for other contaminants of concern in the environment. In the Goff lab, we are examining the spatiotemporal controls on these microplastic-associated contaminants in waterways of upstate New York. We are interested in the colonization of microplastic surfaces by pathogenic bacteria and horizontal transfer of antibiotic resistance genes. We are also examining how microplastics can serve as vectors for heavy metals in aquatic ecosystems. Currently, we are investigating the effects of different weathering conditions on multiple types of microplastics, alongside their effects on the microplastics' ability to absorb heavy metal. We are using Fourier Transform Infrared Spectroscopy (FTIR) to observe how weathering impacts the chemical composition of microplastics. Heavy metal adsorption capacity of the microplastics is being analyzed by inductively coupled plasma mass spectrometry (ICP-MS).  This work will allow us to understand the effects of physiochemical weathering on heavy metal adsorption by microplastics in waterways. 

This work is supported in part by the NYS Center of Excellence in Healthy Water Solutions.