UGA research links inorganic mercury exposure to damaged cell processes

December 22, 2015

Athens, Ga. - University of Georgia research has found that inorganic mercury, which was previously thought to be a less harmful form of the toxic metal, is very damaging to key cell processes.

This study is the first to compare the effects of inorganic and organic mercury compounds at the biochemical, physiological and proteomic levels in any model organism, according to the study's lead author Stephen LaVoie, a microbiology doctoral student. Published in December in the Journal of Biological Inorganic Chemistry, the research looked at how inorganic and organic mercury affected specific molecular processes.

Inorganic mercury from the ore cinnabar was used for centuries against infections; in modern times, humans synthesized organic mercurials as antimicrobials, such as merthiolate.

"Today, most human exposure to inorganic mercury is from dental fillings, and organic mercury exposure is from methylmercury in fish," said study co-author Anne Summers, a microbiology professor in the Franklin College of Arts and Sciences.

Organic mercury exposure is associated with neurological disease, LaVoie explained, whereas inorganic mercury is known to cause neurological, kidney and autoimmune diseases. However, the molecular basis for their distinct toxicity profiles was not understood.

Owing to concern about fish consumption, most research has emphasized organic mercury, assuming it was more toxic, LaVoie said. But comparing them on key cellular processes, he found that inorganic mercury "caused more damage at lower concentrations than organic mercury."

For his study, LaVoie used a common lab strain of E. coli bacteria as a model cellular system. He exposed growing cells to mercury compounds and measured their reactive sulfur called thiols--essential metals and proteins that naturally bind essential metals via amino acid thiols.

"We used a fluorescent probe to detect thiols," LaVoie said. After mercury exposure the thiols decreased more with inorganic than organic mercury. Inorganic mercury was much more efficient at removing iron from iron-dependent proteins than the best organic mercury compound tested.

"As fellow oxygen-breathing creatures, it's important to know that inorganic mercury is more potent than organic mercury in disrupting protein-iron centers such as those we have in our own cells, " Summers said.

"More is being learned about the bacteria in and on our bodies," LaVoie said. "What we ingest affects them, too, and their health affects our health."
-end-
Future work will examine the mercury resistance genes that many bacteria have and how these genes help spread antibiotic resistance genes.

Co-authors of the paper include Darin M. Cowart, Michael K. Johnson and Robert A. Scott of the University of Georgia, Daphne T. Mapolelo of the University of Botswana, and Benjamin J. Polacco and Susan M. Miller of the University of California, San Francisco.

This work was supported by DOE awards ER64408 and ER65286 to AOS and ER64409 and ER65195 to SMM and NIH award GM62524 to MKJ.

To read the full study, "Organic and inorganic mercurials have distinct effects on cellular thiols, metal homeostasis, and Fe-binding proteins in Escherichia coli," visit http://link.springer.com/article/10.1007%2Fs00775-015-1303-1.

University of Georgia

Related Mercury Articles from Brightsurf:

Mercury's 400 C heat may help it make its own ice
Despite Mercury's 400 C daytime heat, there is ice at its caps, and now a study shows how that Vulcan scorch probably helps the planet closest to the sun make some of that ice.

New potential cause of Minamata mercury poisoning identified
One of the world's most horrific environmental disasters--the 1950 and 60s mercury poisoning in Minamata, Japan--may have been caused by a previously unstudied form of mercury discharged directly from a chemical factory, research by the University of Saskatchewan (USask) has found.

New nanomaterial to replace mercury
Ultraviolet light is used to kill bacteria and viruses, but UV lamps contain toxic mercury.

Wildfire ash could trap mercury
In the summers of 2017 and 2018, heat waves and drought conditions spawned hundreds of wildfires in the western US and in November, two more devastating wildfires broke out in California, scorching thousands of acres of forest, destroying homes and even claiming lives.

Removing toxic mercury from contaminated water
Water which has been contaminated with mercury and other toxic heavy metals is a major cause of environmental damage and health problems worldwide.

Fish can detox too -- but not so well, when it comes to mercury
By examining the tissues at a subcellular level, the researchers discovered yelloweye rockfish were able to immobilize several potentially toxic elements within their liver tissues (cadmium, lead, and arsenic) thus preventing them from interacting with sensitive parts of the cell.

Chemists disproved the universal nature of the mercury test
The mercury test of catalysts that has been used and considered universal for 100 years, turned out to be ambiguous.

Mercury rising: Are the fish we eat toxic?
Canadian researchers say industrial sea fishing may be exposing people in coastal and island nations to excessively high levels of mercury.

New estimates of Mercury's thin, dense crust
Michael Sori, a planetary scientist at the University of Arizona, used careful mathematical calculations to determine the density of Mercury's crust, which is thinner than anyone thought.

Understanding Mercury's magnetic tail
Theoretical physicists used simulations to explain the unusual readings collected in 2009 by the Mercury Surface, Space Environment, Geochemistry, and Ranging mission.

Read More: Mercury News and Mercury Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.