Category Archives: Environmental Engineering

Zebrafish sentinels: studying the effects of cadmium on biology and behavior

Cadmium exposure is on the rise

There’s a good chance you might have touched cadmium today. A heavy metal semi-conductor used in industrial manufacturing, cadmium is found in batteries and in some types of solar panels. Fertilizers and soil also contain cadmium because it is present in small levels in the Earth’s crust. The amount of cadmium in the environment is increasing because of improper disposal of cell phone batteries, contaminating groundwater and soil. This is a problem that impacts people all over the world, particularly in developing countries.

Plants take up cadmium from the soil, which is how exposure through food can occur. Leafy greens like spinach and lettuce can contain high levels of cadmium. From the soil, cadmium can leach into groundwater, contaminating the water supply. Cadmium is also found in a variety of other foods, including chocolate, grains and shellfish, as well as drinking water.

Cadmium has a long half-life, reaching decades, which means that any cadmium you are exposed to will persist in your body for a long time. Once in the body, cadmium ends up in the eyes or can displace minerals with similar chemical properties, such as zinc, copper, iron, and calcium. Displacement can cause grave effects related to the metabolism of those minerals. Cadmium accumulation in the eyes is linked to age-related macular degeneration, and for people in the military and children, elevated cadmium is linked to psychosocial and neurological disorders.

Read more about cadmium in the food supply:



Using zebrafish to study the effects of cadmium

Delia Shelton, a National Science Foundation post-doctoral fellow in the Department of Environmental and Molecular Toxicology, uses zebrafish to investigate how cadmium exposure in an individual affects the behavior of the group. Exposing a few individuals to cadmium changes how the group interacts and modifies their response to novel stimuli and environmental landmarks, such as plants. For example, poor vision in a leader might lead a group closer to predators, resulting in the group being more vulnerable to predation.

Zebrafish

As part of her post-doctoral research, Delia is asking questions about animal behavior in groups: how does a zebrafish become a leader, how do sick zebrafish influence group behavior, and what are the traits of individuals occupying different social roles? These specific questions are born from larger inquiries about what factors lead to individual animals wielding inordinately large influence on a group’s social dynamic. Can we engineer groups that are resilient to anthropogenic influences on the environment and climate change?

Zebrafish

Zebrafish are commonly used in biomedical research because they share greater than 75% similarity with the human genome. Because zebrafish are closely related to humans, we can learn about human biology by studying biological processes in zebrafish. Zebrafish act as a monitoring system for studying the effects of compounds and pollution on development. It is possible to manipulate their vision, olfactory system, level of gene expression, size, and aggression level to study the effects of pollutants, drugs, or diseases. As an added benefit, zebrafish are small and adapt easily to lab conditions. Interestingly, zebrafish are transparent, so they are great for imaging. Zebrafish have the phenomenal ability to regenerate their fins, heart and brain. What has Delia found? Zebrafish exposed to cadmium are bolder and tend to be attracted more to novel stimuli, and they have heightened aggression.

Read more about zebrafish:

ZFIN- Zebrafish Information Network – https://zfin.org/
Zebrafish International Research Center in Eugene Or – http://zebrafish.org/home/guide.php



What led Delia to study cadmium toxicity in zebrafish?

As a child, Delia was fascinated by animals and wanted to understand why they do the things they do. As an undergrad, she enjoyed research and pursued internships at Merck pharmaceutical, a zoo consortium, and Indiana University where she worked with Siamese fighting fish. She became intrigued by social behavior, social roles, and leadership. Delia studied the effects of cadmium in grad school at Indiana University, and decided to delve into this area of research further.

Delia began her post-doctoral work after she finished her PhD in 2016. She was awarded an NSF Postdoctoral Fellowship to complete a tri-institute collaboration: Oregon State University, Leibniz Institute for Freshwater Ecology and Inland Fisheries in Berlin, Germany, and University of Windsor in Windsor, Ontario. She selected the advisors she wanted to work with by visiting labs and interviewing past students. She wanted to find advisors she would work well with and who would help her to accomplish her goals. Delia also outlined specific goals heading into her post-doc about what she wanted to accomplish: publish papers, identify collaborators, expand her funding portfolio, learn about research institutes, and figure out if she wanted to stay in academia.

Research commercialization and future endeavors

During her time at OSU, Delia developed a novel assay to screen multiple aspects of vision, and saw an opportunity to explore commercialization of the assay. She was awarded a grant through the NSF Innovation Corps and has worked closely with OSU Accelerator to pursue commercialization of her assay. Delia is now wrapping up her post-doc, and in the fall, she will begin a tenure track faculty position at University of Tennessee in the Department of Psychology, where she will be directing her lab, Environmental Psychology Innovation Center (E.P.I.C) and teaching! She is actively recruiting graduate students, postdocs, and other ethnusiatic individuals to join her at EPIC.

Please join us tonight as we speak with Delia about her research and navigation of the transition from PhD student to post-doc and onwards to faculty. We will be talking to her about her experience applying for the NSF Postdoctoral Fellowship, how she selected the labs she wanted to join as a post-doc, and her experience working and traveling in India to collect zebrafish samples.

Tune in to KBVR Corvallis 88.7 FM or stream the show live on Sunday, April 7th at 7 PM. You can also listen to the episode on our podcast.

Can soil bacteria clean up our toxic messes?

Thousands of sites across the US are contaminated with chemical solvents that have been used for decades in industrial processes. These solvents can leach into groundwater and create plumes up to several miles long. 1,4-dioxane, a probable human carcinogen, is often present in groundwater contaminant plumes because of its historical use in degreasing heavy machinery, but it’s also present in trace amounts in products as varied as laundry detergents, deicing agents, cosmetics, and even in food.

There’s good news and bad news here: The Resource Conservation and Recovery Act, enacted in 1980, established laws for the management and disposal of hazardous wastes, meaning new releases to the environment have diminished considerably. Decontamination of chlorinated solvents often involves pumping groundwater to the surface and removing the contamination through volatilization or adsorption. However, this process is expensive, time- and energy-consuming, and ineffective at removing some chemicals, like water-soluble 1,4-dioxane.

Some jobs require the help of friends. In this case, for Hannah Rolston, a fifth-year PhD student in the Department of Environmental Engineering working with Dr. Lewis Semprini, these friends are soil bacteria that are able to naturally degrade this carcinogen. Bioremediation, or the practice of putting these bacteria to work to degrade contaminants, offers some hope in cases like these. Sometimes they can degrade certain pollutants all by themselves (called natural attenuation), but when you’re dealing with carcinogens in areas with people nearby, you want to use an engineered approach to make sure this process goes as quickly and efficiently as possible.

Hannah explained to us that not all compounds are easily degraded by bacteria, and even though some will consume 1,4-dioxane as food, environmental concentrations are not enough to sustain their growth (though remain harmful to humans). To work around this, she has been using a strategy called cometabolism. This involves adding a different carbon source into the groundwater plume for the microbes to eat–ideally, one that will cause the bacteria to produce enzymes that not only degrade the food source, but the 1,4-dioxane as well. This can be tricky, and not only in an engineering sense: you need to know enough microbial metabolism to be sure they’re not converting the hazardous compound into something even worse.

Hannah collecting groundwater samples from test wells at the OSU motor pool.

Using soil samples from two contaminated sites in Colorado and California, Hannah and the Semprini group are using isobutane (yes, the same gas you use for your camp stove) to nourish the native microbial communities so that they produce a type of enzyme called a monooxygenase. She has observed the 1,4-dioxane levels decrease in these enrichments. Preliminary work shows the bacteria convert 1,4-dioxane all the way to carbon dioxide–completely benign compared to what we started with.

Hannah began her undergraduate at Seattle University as an international studies major interested in a career in diplomacy. Feeling her first year of humanities classes provided her a wide breadth of knowledge but didn’t give her applicable skills, she transferred to environmental engineering, where she became interested in groundwater and hazardous waste remediation. After graduation, she worked for the US Army Environmental Command, working with army installations across the country to comply with environmental regulations.. When the spreadsheets and desk work didn’t quite live up to its expectations, she knew it was time to seek out graduate programs where she could put her engineering background and interest in hazardous waste remediation to work.

When she’s not tricking microbes into consuming carcinogenic contaminants, Hannah can be found road biking and doing ceramics at the OSU craft center. She is also involved in the OSU Chemical, Biological, and Environmental Engineering Graduate Student Association and the OMSI Science Communication Fellowship program. To hear more about her research and journey to graduate school, tune in to Inspiration Dissemination Sunday August 26th at 7pm on 88.7 FM, or stream the show live.

Antibiotic resistance: The truth lies in the sludge

 

Genevieve experiencing Vietnamese culture at Sam Mountain in the Mekong Delta

Did you know that about 30% of people here in Oregon have septic tanks? Why is that relevant to this week’s topic you ask? Our guest this week on Inspiration Dissemination, Genevieve Schutzius is an Environmental engineering masters student in the College of Engineering interested in waste water management. Genevieve is working with Dr. Tala Navab-Daneshmand as part of the Navab lab. The lab’s mission is to identify the fate and transmission pathways of pathogenic and antibiotic-resistant bacteria from wastewater systems to environmental reservoirs, and to design engineered systems and interventions to reduce the associated human health risks.

 

 

A beautiful sunrise over the Saigon River in District 4 of Ho Chi Minh City.

Recently, Genevieve spent a term abroad working on a project that is in collaboration with Dr. Mi Nguyen at Nguyen Tat Thanh University in Vietnam. The purpose of the study is to identify the human health risks associated with the spread of infectious bacteria resistant to antibiotics in areas with high septic tank use. Specifically, Genevieve’s project is to identify the fate of antibiotic resistance in soils and waters as recipients of untreated septic sludge.

 

Genevieve sampling a sludge-filled canal using a fashioned “sampling stick” from an abandoned bamboo fishing pole in the northwest of Ho Chi Minh City.

She did this by collecting 55 soil samples from canals, rivers, parks, and fields in Ho Chi Minh City, then plated dilutions of these samples to quantify the number of E. coli, which is a common indicator of fecal contamination. She selected E. coli colonies and brought them back to her lab at OSU, where she performed the disk diffusion method. The disk diffusion method involves plating isolated bacteria across an entire agar plate and see how it grows in the presence of disks containing antibiotics. She tested them against 9 different antibiotics, finding that 69% of 129 isolates were resistant to more than two! She is also conducting a microcosm study to see how resistant bacteria thrives in soils and in different temperature environments. Soon, she will determine the presence of absence of antibiotic-resistant genes in her isolated bacteria using PCR to amplify genes.

Samples mixed with bacteria including chosen E. coli isolates (circled).

Why Vietnam? Well Vietnam has high levels of septic tank use and out of 11 Asian countries surveyed, Vietnam also had the highest levels of antibiotic resistance in patients due to the ease at which they are acquired. A survey Genevieve assisted in implementing while in Vietnam opened her eyes to just how easy it is to get antibiotics and how much they are used among citizens.

 

A plate showing how resistant this particular E.coli isolate is to ampicillin (full resistance), streptomycin (full resistance), gentamicin (mostly resistant), and imipenem (not resistant – “last resort” antibiotic.

 

Originally from Colorado, Genevieve acquired her undergraduate degree in environmental engineering at the University of Colorado Boulder where she became interested in waste water management. She always knew that she wanted to end up in the pacific northwest and after finding out about Oregon State Universities program she decided that the environmental engineering program suited her interests. Following completion of her masters degree she hopes to continue to travel and find work in the humanitarian/non-profit public health and sanitation sector.

In Genevieve’s free time, she enjoys experimenting with her cooking, typically with different types of Indian spices. She also enjoys partaking in activities such as yoga, snowboarding, playing piano, and singing.

 

Tune in to 88.7 FM at 7:00 PM Sunday evening to hear more about Genevieve and her research on antibiotic resistance in areas of high septic tank use, or stream the program live.