Eliana Jacobson ’16 organizes her life around those of fruit flies. “What most people don’t understand about the work in the lab of Brian P. Lazzaro, Entomology, is that you have to live on the fruit flies’ schedules—if they eclose on a Sunday, then that’s when you have to be in,” she says. But she’s never upset about having to spend extra time working under Professor Lazzaro, whose work focuses on the evolutionary genetics of insect–pathogen interactions.
The Research and an Opportunity to Be Named an Author on Scientific Papers
“It’s a very community-oriented lab, which makes working there fun,” Jacobson says with a laugh. She works closely with a postdoctorate student, Moria Chambers, looking at how fruit flies develop immunity and resistance to pathogens. They recently published a paper titled “Thorax Injury Lowers Resistance to Infection in Drosophila melanogaster,” which detailed their research on bacterial infection in fruit flies (D. melanogaster).
The insects are vulnerable to death post-infection when they are injured in their thorax, separate from a site of entry for the bacteria. Prior to their work, it had not been thought that remote wounding to the fruit fly (thorax, abdomen, and so forth) would affect bacterial proliferation. “Some labs focus on just the abdomen or the thorax, but we wanted to see what would happen if we compare both as our point of infection,” says Jacobson. What they realized was that location didn’t in fact matter—so long as there was an injury to the thorax, a fruit fly would be more susceptible to death by infection.
Because of the success of their first round of research, they’re completing a second article, which will explicate the methods they’re applying to this work (“Quantitative Bacterial Infection and Immune Defense Phenotypes in D. melanogaster,” Journal of Visualized Experiments), and beginning work on another publication. For this paper they’re dealing with roughly 50 “bacterial determinants that cause the fruit flies to clear the infection, or develop acute or chronic infections.” To do this, Jacobson and Chambers, under Professor Lazzaro’s direction, are infecting the same breed of fruit fly with 50 different strains of bacteria. They then look at bacterial loads and survival rates, essentially tallying up the fruit flies that have survived and those that have died.
Catering to the Flies’ Every Need
“It’s weird to think about what would make flies ‘happiest’ and putting significant effort into creating conditions for them that accomplish this, but that’s what we do,” laughed Jacobson. The flies are kept in “optimal conditions” for their survival: because they’re cold-blooded, 25 degrees Celsius is their ideal temperature. Some of the bacteria used for these experiments are bacteria that infect humans, so they respond better to warmer conditions (which in humans are provided by body heat) and are grown at 37 degrees. The lab incubator is set to light and dark cycles that roughly mimic natural, sunlight cycles: twelve hours of light, twelve of dark.
“It’s been a fascinating project,” says Jacobson, “especially because we’ll get to work collaboratively with other labs to expand our understanding of the data and the complexities at work.” One such collaboration is with Angela Douglas, Entomology, whose lab will be mapping genes for the project to see how the infections work on a genetic level.
“It’s been a fascinating project,” says Jacobson, “especially because we’ll get to work collaboratively with other labs to expand our understanding of the data and the complexities at work.”
Experiment cycles last two weeks, because that is roughly the time to reach stability in bacterial load and survival of their subjects, the fruit flies. They administer the infection of the abdomen or thorax at the beginning of this period, and then make observations on the rate of survival three times during the given time frame. To do the bacterial count, they grind up the fruit flies and streak them on LB agar plates. The Lazzaro lab is using the same statistical methods as before, but at the end of the year, they’ll hand over the data they have collected from innumerable repetitions of this experiment to the Douglas lab for analysis.
Jacobson wants to further focus this research, using what information the Douglas lab gives them, to look at why some fruit flies contract a chronic infection: “Some of the flies are given a much lower bacterial count and they die, whereas some are given quite a bit higher and survive. The cause of this is something that remains unknown.”