Geologists Use Biotools To Understand Geosystems; Goal Is To Control Toxin Mobility

Virginia Tech researchers are looking at the mobility of bacteria andof heavy metals in surface and ground water. Geosciences professorMichael Hochella Jr. will present recent findings at the GeologicalSciences of America national meeting in Salt Lake City Oct. 16-19.

How do we understand when bacteria will stick? What are thesticking efficiencies of bacteria on minerals? If they are high, thereis a good chance it will be bound by minerals. If they are low, thebacteria will bounce off. "That is a frequent theme with toxins," saidHochella. "How mobile are they? Will they stick on surfaces ortransport through water or air? Mobility is not good.

"Geologists are now becoming microbiologists in order todiscover how biosystems affect geosystems," he said. "We study bacteriaand other microorganisms in sophisticated ways. Geoscience Ph.D.students take courses in microbiology and biochemistry and applybiotools to geosystems."

Ph.D. student Tracy (Cail) Bank did her dissertation researchon the sticking efficiencies of Enterococcus faecalis bacteria, whichcauses opportunistic urinary tract infections and wound infections, andis becoming antibiotic resistant. "We also picked it for this researchbecause it is spherical," Hochella said.

Bank attached a single bacterial cell as the tip of acantilever in an atomic force microscope, lowered it to a mineralsurface in water, and measured the exceptionally small approach andadhesion forces present. She used a mathematical model (the interactionforce boundary layer model) to determine the sticking efficiencies.Thus, she has provided for the first time a direct measurement of howlikely those cells are to stick to those surfaces.

She used a silica glass surface, which mimics quartz, thesingle most common mineral in the curst of the earth, and the principalmineral in sandstones. "Water flowing through sandstone is a commonoccurrence," Hochella said.

Bank altered the pH of the water and discovered significant differencesin stickiness as a result. As the water went from neutral to slightlyacidic, the sticking efficiencies increased dramatically.

Bank's unique research with E. faecalis took several years. She nowworks at the environmental sciences division of Oak Ridge National Lab."It is up to others to test other minerals," Hochella said.

He will also describe transmission electron microscopetechniques used to study nanoparticles in surface water, groundwater,and drinking water and to determine the role of such particles intransporting heavy metals. Hochella discovered nanoparticles bindingheavy metals in the course of his research on transport of such metalsfrom the Clark Fork Superfund Complex in Montana.

The talk, "New insights into the identity, characteristics, andtransport of small biotic and abiotic particles in the critical zone,by Hochella and Bank, will be presented at 9: 15 a.m. on Wednesday,Oct. 19, at the Salt Palace Convention Center room 251 AB. VirginiaTech faculty members and students will present more than 30 papers atthe GSA national meeting.

Learn more about Hochella's work at http://www.geol.vt.edu/profs/mfh/mfh-r.html