Since the spring semester of her freshman year at Rice University, including the summer months, Jessica Ha has been treating bacterial cultures in petri dishes with varying concentrations of D-amino acids, and recording the results.
"I really love the research. You feel ownership of the work you're doing. I didn't know that until I came to Rice. Even before I had decided on a major I was doing real research," said Ha, a sophomore in chemical and biomolecular engineering.
In collaboration with a graduate student, Ha works in the lab of Qilin Li, assistant professor of civil and environmental engineering and associate director of Nanotechnology Enabled Water Treatment (NEWT) Systems. Li's research focus is water, and Ha's bacterium and others jeopardize its quality and reliability of supply.
Biofilms are groups of microorganisms that clump together and form a glue-like matrix of extracellular polymeric substance (EPS)—in the vernacular, slime. These sugary molecular strands are related to the slick coating that develops on stones in a river and the plaque that forms on teeth. Biofilms commonly grow on the inner surfaces of water and sewage pipes, and cause clogging, reduced flow and corrosion. One such bacterium is Pseudomonas aeruginosa, Ha's research subject in Li's lab.
D-amino acids are found in nature, often as a component of peptide antibiotics and in the walls of some microorganisms. Li and her colleagues are exploring the impact of D-amino acids on this single biofilm-creating bacterium. Preliminary research suggests they may be effective in controlling them. How effective are they? What is the optimal concentration of D-amino acids? Is any risk associated with their use?
The impact of biofilms on health, water quality, corrosion and power generation efficiency is estimated to cost the U.S. billions of dollars each year. Biofilms can contain different types of microorganisms besides bacteria—archaea, protozoa, fungi and algae. Li and Ha are engaged in the painstaking work of determining how one species reacts to different concentrations of D-amino acid.
"We think the D-amino acid interferes with their motility, their ability to move. We don't know the exact mechanism of how the D-amino acid affects biofilms, but motility is a possibility. There's still a lot of work to be done on this. The science isn't settled," Ha said.