Pinar Kohlmeier walked through the grass, still wet with morning dew, stopping at a crepe myrtle tree. Carefully, she searched through the branches, pulling down a large plastic bottle housing more than a dozen fruit flies.
Fruit flies are a pest to most people. But to husband-and-wife researchers Philip and Pinar Kohlmeier, the flies provide vital clues to understanding health disparities between people in high- and low-income neighborhoods.
A research team led by the Kohlmeiers is conducting a pilot study of fruit fly health through their lab in the University of Memphis’s Department of Biological Sciences that holds promise for understanding health outcomes in Memphis, one of America’s poorest cities.
Preliminary results suggest that flies in low-income neighborhoods are less healthy. They are less heat-resistant and have lower fertility rates than their counterparts in higher-income neighborhoods.
The Kohlmeiers chose to study fruit flies because ethical and time considerations that complicate direct studies on humans in trying to understand how income inequality and other factors affect health disparities. Studying fruit flies is less complicated. For example, it’s easier to isolate variables like heat or lack of nutritious food for fruit flies than it is for humans. Studying effects over generations is simpler too, as fruit flies can produce offspring in days.
“We can expose them to one or two factors associated with low- or high-income lifestyle,” said Philip Kohlmeier, who holds a PhD in biology. “Then (we can) see on a molecular level how does this translate into physiological (changes). So, we can produce predictions to the mouse model, and from there we can go to humans.” The mouse model is the use of a laboratory mouse to mimic human physiology, diseases or genetics because they both are biologically similar, sharing much of the same DNA.
With data from this research, Philip and Pinar hope to help build a hypothesis for future studies, as well as the possibility of developing treatments or drugs for conditions affecting people hindered by income disparities.
When choosing which neighborhoods to study, Philip and Pinar consulted old redlining maps to identify disadvantaged neighborhoods. The low-income communities of Orange Mound and Binghampton, and the higher-income communities of Hedgemoor and Chickasaw Gardens, as well as the city of Germantown, were chosen. The researchers placed custom-built fly traps, made of plastic bottles with an entry for the flies with sticks and fruit inside the bottle, across these neighborhoods. Signs attached to the traps asked people not to throw them out, explaining the pilot study, called MEM-FLY, which is supported by a $5,000 grant from UofM’s Institute for Agricultural and Conservation Research and Education.
Using a “citizen science approach” in which students and community members participate in data collection and analysis, Philip, Pinar, and student researchers visited community centers in Orange Mound and Binghampton to ask people if they could place fly traps around their yards. When they got permission, they would usually place the traps near trash bins or in trees.
In high-income neighborhoods, where community centers are scarce, researchers placed them in public spaces that best match trap placement in low-income neighborhoods. The researchers retrieve the traps within a few days after placing them.
“If we would go inside of the houses, we would want to put the traps near their trash cans,” Pinar Kohlmeier said, “The good thing is, some days the trash collectors are collecting trash, the bins are out, and I put (the trap close to the bins), so it is as good as I put it in their house.”
When flies are caught in traps, they are brought into the lab for testing. Researchers sort out fruit flies, known in scientific lexicon as the Drosophila melanogaster, from other species caught in the trap. However, researchers do not have long to study the flies before their bodies adjust to lab conditions.
Researchers examine how many eggs the flies can produce. They also examine whether female flies are more likely to produce offspring with flies from high-income or low-income neighborhoods.
The study so far has mainly examined the roles of food deserts — areas with limited access to affordable, nutritious food — and heat islands, urban areas heavy with pavement, roads, and buildings that trap heat and have little greenery like trees or plants to reduce the health-debilitating effects of higher temperatures.
Flies use green spaces to escape heat. They can live comfortably at temperatures up to 77 degrees. Once their body temperature reaches 86 degrees, they start to suffer physiological damage.
Orange Mound and Binghampton are both heat islands, whereas Hedgemoore, Chickasaw Gardens and Germantown are not. Orange Mound and Binghampton have about 15% less green space than Germantown, the higher-income area with the least green space in the study, according to Environmental Protection Agency data.
“There are a ton of factors that can play a role (in fruit fly health). It’s like soil contamination and air pollution,” Philip Kohlmeier said. “It’s the chemicals the house is painted with that are often cheaper and hazardous; heat is a huge factor as well.”
According to a past UofM study, there is more pollution in the low-income neighborhoods researchers examined than in the high-income neighborhoods.
The flies’ exposure to heat and pollution has led to lower fertility in male flies in low-income neighborhoods; researchers are still studying whether this is due to weaker sperm, a lower sperm count, or both.
“Male flies are less healthy in terms of producing the next generation of offspring,” Pinar Kohlmeier said. That mirrors outcomes in humans, she said. Humans in low-income neighborhoods have higher rates of premature birth rates and babies born underweight.
Orange Mound and Binghampton are also food deserts. There is a lack of places to buy nutritious foods, something both humans and flies need. Access to grocery stores is limited.
“Because of the high car dependency in the U.S. in general and specifically (in Memphis), you are immediately less mobile if you don’t have a car, and if you look at how grocery stores are distributed in the city, they are clustered in high-income areas,” Philip Kohlmeier said.
Fruit flies rely on yeast, which grows on bread or old fruits and vegetables, and sugar. According to a study from the University of Michigan, when flies lack both yeast and/or sugar, they will suffer health consequences, including shorter life spans.
“People don’t have a car, so the only alternative is to go to convenience stores, gas stations, to buy food there, like chips, corn flakes, beef jerky, and some soda. So, they don’t have the same access. I mean, we’re not even talking financial access here. It’s logistic access to grocery stores,” Philip Kohlmeier said. “In canned food, there’s also a lot of chemicals given to the food that we know can impact your physiology.”
The research is ongoing but is paused for the winter. When experiments start again in May, researchers will be testing factors like food insecurity and pollution when gauging fruit fly health.
Philip Kohlmeier has been an assistant professor at the UofM for three years. His PhD, from Germany’s Johannes Gutenberg University Mainz, involved researching the transcriptomic and epigenetic mechanisms of behavioral specialization in ants. He has 19 publications, seven of them about fruit flies.
Pinar Kohlmeier is a PhD candidate at the University of Groningen, the Netherlands. While this study isn’t in her PhD research focus, it fits within her goals of bridging the communication gap between scientists and the public, along with doing outreach to educate the public.
“This project was kind of unique because we needed to collect flies from around the city and we needed to communicate to people,’’ she said. “We just kind of boost (communication) skills to be able to talk about research, link it with societal needs, for example, what fly health means in terms of human health, especially with kids, in low-income areas.”
