Two hundred years later, biology professor Manuel Ospina-Giraldo is still thinking about the Irish Potato Famine. Or, the microbe behind it, that is.
“That pathogen is still a major, major issue in agriculture,” he said about Phytophthora infestans, the microorganism that causes potato blight.
We know that the blight results in a loss of over $6 billion globally per year. We don’t yet know exactly how the pathogen gets into plant cells to cause damage.
Ospina-Giraldo — who studies phytopathology, or plant disease — is growing our knowledge of this mechanism.
“We are trying to figure out, at the DNA level, what genes are involved in this process,” he said.
Phytophthora infestans is an oomycete, a fungus-like organism that used to be classified as a fungus itself. One difference between the two groups is how they penetrate the cell wall of plant cells.
Fungi use a needle-like structure, whereas the oomycete is not strong enough to do the same. Ospina-Giraldo discovered that it instead uses enzymes that “weaken the cell wall significantly in such a way that any potential mechanical penetration would be easy.”
Imagine trying to punch through a brick wall. These enzymes make a brick wall more like a sheet of paper for the oomycete, making it easier to rip through, no matter how many arm days it skipped.
Ospina-Giraldo is currently focused on identifying which 435 “candidate” genes potentially encode the enzymes and other parts of the mechanism that allow the pathogen to enter the plant cell.
He said that so far, there are “maybe close to 100” of those genes that have been confirmed to play a role.
“We still continue characterizing these genes, one group at a time,” Ospina-Giraldo said.
Students in the research lab are often assigned one of these genes.
“He wanted us to pick a gene to really sink our teeth into and to really study and understand and explore,” said Gabriel Guzman ’26, who chose an enzyme inhibitor.
To characterize a gene — to determine its different features like sequence, function and expression — it first needs to be multiplied enough to be able to study.
“From the actual organism that you’re working on, you would never be able to do that because you only have one copy of the gene,” Ospina-Giraldo said. “That’s not enough.”
He uses a method called cloning, in which the target gene is inserted into a bacterium to be replicated as the bacterium replicates itself.
“It’s cool that we’re using E. coli to isolate the gene that we’re looking for — that’s just wild,” said Haley O’Shea ’26, another student in the lab.
But this procedure is “only the beginning” of experimentation, Ospina-Giraldo said. The gene can then be extracted from the multiplied bacterial cells for further analysis and experimentation.
Alanna Haldaman ’25 is doing an independent study with Ospina-Giraldo focused on the expression levels of her gene across the pathogen’s infection of potato plants.
“I learned a lot about the importance of pipetting and how even the smallest amount can throw off the entire experiment,” she said. Haldaman cited how a procedure she frequently performs for gene amplification, quantitative PCR, requires very exact repeated volumes.
Aside from the science, the most “exciting thing to see” for Ospina-Giraldo is seeing his research students get excited about what they’re doing.
“I have an incredible satisfaction when I see a student being excited about the project, or about projects in general, in the lab,” he said.
“He wants you to succeed and understand what you’re doing,” O’Shea said about Ospina-Giraldo. “He’s really good about taking a step back and having you do it.”
