Ticks are vectors for several serious diseases (meaning that they can transmit these diseases to humans), including Lyme disease, babesiosis, and anaplasmosis. Melissa Yost-Bido ’19 studied something called Haller’s organs: chemosensory organs (essentially, a very special type of smell) that ticks have on their front legs, and  that is thought to help them detect pheromones, carbon dioxide, and infrared radiation. As you can guess, all that ticks really care about, is how to find a host (such as a mouse, or a human), to attach to them, and  feed on their blood. Being able to detect animal smells and heat would definitely help here!

Many methods of tick-borne disease prevention that are used now, harm not only ticks, but also other, good, beneficial organisms. If we learn more about the Haller’s organ, we can try to find new ways to fight ticks, by making sure that they cannot find new hosts. Melissa studied the ability of the Haller’s organ in blacklegged ticks (Ixodes scapularis; the nastiest ticks around here) to detect infrared light. She collected local ticks, separated them into groups, and then either left their Haller’s organs intact, or removed them. Then Melissa exposed each tick from each group to infrared light (heat), and recorded the distance that each tick moved towards the source of infrared radiation. She found that ticks with a Haller’s organ traveled farther towards the heat, compared to those that had their Haller’s organs removed. This suggests that Ixodes ticks can use Haller’s organs to detect warm bodies, which is something nobody had ever shown before!

We live in the era of antibiotic resistance: old, familiar antibiotics, that used to work so well in the past, are no longer guaranteed to kill harmful bacteria, as the bacteria evolve new ways to fight back and survive the treatment. Because of that, now, more than ever, it is important to study the fundamentals of gene regulation in bacteria, with a hope to find new ways to control them.

Riboswitches are a unique mechanism of gene regulation that is used by bacteria, fungi, and plants. A piece of RNA with a riboswitch changes its shape depending on what chemicals are present in the cell, which in turn changes what proteins are produced by the bacterium. Riboswitches were shown to be critical for the bacterial survival, which means that in the future, we can try to use them as targets for the development of new pharmaceuticals. With the guidance from Dr. Gabriel Perron and Dr. Swapan Jain, Rachael Mendoza ’19 used bioinformatic tools to identify and classify the riboswitches in thirty strains of a certain bacterial species (B. subtilis). She described the diversity of riboswitches in these strains, and put forth some interesting hypotheses about how this information can inform development of future medical treatments.

For her senior project, Lucy Christiana ’19 built a computer simulation of plant community dynamics. Lucy studied how plants would grow if they experience a phenomenon called “plant-soil negative feedback”. Despite a scary name, the idea of this effect is rather simple: imagine that every growing plant is attacked by some “bad stuff” living in the soil, such as pathogenic fungi that try to weaken or kill the plant. As a plant is growing , these fungal pathogens will multiply in the soil around it, making this patch of soil kind of hostile to this plant species. Any seed from this species, for example, will have a hard time surviving in this particular patch of soil, just because it is so rich with “bad fungi”. A different plant species, however, will have no problem living there, as it will be immune to pathogens (each plant species comes with its own list of enemies, so pathogens of one species don’t necessarily harm the other).

As you can imagine, this can really change how plants grow, and it would probably improve biodiversity: even if one plant species is a strong competitor, it will soon be weakened by local pathogens, allowing other species to grow in its place. Lucy was interested in how these negative feedbacks shape the emerging plant community, and she used over 30 years of historical vegetation data from a particular long-term field experiment in Lawrence, Kansas. Lucy built a cellular automata model for one of the species described in this experiment (Ambrosia artemisiifolia, aka common ragweed), and compared predictions of her model to real data. This study is a step towards a more integrated analysis of spatiotemporal patterns of plant community assembly dynamics, and it can help us to understand how plants interact with each other, and how these interactions shape the landscapes that surround us.