Detection and Recovery of Targeted Bacteria

Sources: Romy Chakraborty and Dan Hawkes

A. Acridine orange stained image of lab consortia (MMC) in subsurface injection well water from100H site at Hanford before IMS. B. Acridine orange stained image of curved Desulfovibrio strain RCH1 cells attached to paramagnetic beads. C. Acridine orange stained image of recovered D. vulgaris RCH1 cells post-IMS.

Sulfate-reducing bacteria (SRB) are found everywhere—in soil and sediment, fresh and marine waters, hot springs and geothermal springs, petroleum and natural gas wells, and in sewage. These microbes play important roles in biogeochemical processes and aid in the bioremediation of toxic wastes. But SRB can also adversely affect important man-made resource systems and the environment. For example, SRB thrive in deep wells, plumbing systems, water softeners, and water heaters. By producing hydrogen sulfide as an end product, SRB cast an undesirable rotten egg smell, thus compromising water quality. SRB are also responsible for corrosion of the cast-iron stainless-steel pipelines frequently used in sewage treatment facilities and in petroleum reservoirs. U.S. losses as a result of SRB corrosion damage have been estimated to be $4–6 billion/year.

Recently, a team of researchers led by ESD’s microbiologist Romy Chakraborty (and including ESD’s Terry Hazen, Dominique Joyner, Mary Singer, and Tamas Torok) has been investigating Desulfovibrio vulgaris (D. vulgaris), a well-characterized sulfate-reducer known to reduce metals, and which has commonly been detected at DOE contaminated sites—such as the uranium-contaminated Oak Ridge, Tennessee, Field Research Center and the chromium-contaminated 100H site at Hanford, Washington. Chakraborty and her team used immunomagnetic separation (IMS), a rapid, efficient, isolation technique used in medical and food microbiology, but not previously in environmental studies, due to stringent growth and handling requirements.

In work described in Chakraborty et al. (2011), the research team successfully isolated D. vulgaris and closely related cells from a collection of several microorganisms. They also showed that IMS can be effectively used in conjunction with transcriptomics analysis (the study of active gene expression by a cell) of the separated target cells. As developed for anaerobes like D. vulgaris cells, IMS has shown to be effective in rapidly separating and detecting target cells, and is also nondestructive. The rapid separation and detection effected by IMS does not require expensive equipment, and can be modified to separate or detect multiple bacterial species simultaneously (facilitating subsequent imaging or application of specific enzyme tests or culture-based methods).

The team’s ultimate goal is to develop a field-deployable version of IMS that enables the detection of target microorganisms from often low-biomass environmental samples, which can then be further processed in various –omics studies (e.g., transcriptomics, defined above, and metabolomics, the study of metabolite profiles as produced in a cell) studies to better characterize their metabolic properties. A field-deployable version of IMS would allow for a timely analysis of changing gene profiles of organisms as they are exposed to fluctuating factors in the environment, be they responses to changing temperature, pH, growth substrates, electron acceptors, or nutrient fluxes.

 

Citation:

Chakraborty, R., T.C. Hazen, D.C. Joyner, K. Kusel, M.E. Singer, J. Sitte, and T. Torok (2011), Use of immunomagnetic separation for the detection of Desulfovibrio vulgaris from environmental samples. Journal of Microbiological Methods (in press); published online, DOI:10.1016/j.mimet.2011.05.005.