New paper by a recent Bard graduate Liz Miller ’18, in collaboration between labs of Dr. Collins and Dr. Perron:
Miller, E. C., Perron, G. G., & Collins, C. D. (2019). Plant‐driven changes in soil microbial communities influence seed germination through negative feedbacks. Ecology and evolution, 9(16), 9298-9311.
As plants grow, fungal pathogens accumulate around the roots of plants. Negative plant-soil feedbacks occur when these pathogens reduce the success of individual plants belonging to the same species. As a consequence, pathogens regulate the density of their specific plant hosts, and plants tend to grow best when their neighbor is a different plant species.
While seedlings and adult plants are known to suffer from these negative feedbacks, much less is known about the effect of species-specific pathogens on seeds. We tested whether seeds of seven different species experienced higher mortality in soils “conditioned” by plants of their own species (soils where pathogens were allowed to accumulate over time around the plant roots), versus soils conditioned by a different species. We also used metagenomics tools to identify potential pathogens driving the feedbacks.
We discovered that seeds of several grassland plant species experience negative feedbacks, i.e., the die more in their own soil than in soil of neighboring species. We also found that the putative pathogens driving these feedbacks differed depending on which species conditioned the soil a seed was buried in. Our results suggest that negative feedbacks at the seed stage may play a role in population persistence and plant diversity, and that the role of particular pathogens for driving feedbacks may depend on which plant species are in the neighborhood.
We are excited to learn that the Tick Project, led by Bard professor Felicia Keesing, is now featured by The New Yorker magazine!
Check out this beautiful story by Micah Hauser:
Keesing said, “I don’t like ticks any more than the next person, but I do admire them. They are survivors. Those things live for two years and eat three times. They can survive ninety-five-degree, humid, horrible summers and twenty-below winters. If you are going to root for the little guy—”…
“And their saliva!” Ostfeld interrupted. “They have a pharmacopoeia in their saliva. How do you stay attached to an animal without being detected, shrugged off, squished, or broken in half, for up to a week or so?
Read more on the New Yorker website!
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.
The Ecological Society of America (ESA) has named Bard Biology faculty Felicia Keesing as one of its 2019 Fellows. The Society’s fellowship program recognizes the many ways in which its members contribute to ecological research and discovery, communication, education and pedagogy, and management and policy. Fellows are members who have made outstanding contributions to a wide range of fields served by ESA, including those that advance ecological knowledge in academics, government, non-profit organizations, and the broader society.
The Society cited Keesing for pioneering research in the ecology of infectious diseases and community ecology of African savannas, and pedagogical research that she has integrated into a vision and practice of college science teaching for enhancing scientific literacy.
Read the full press-release here: https://www.bard.edu/news/features/?id=280
1/31 – Introduction
2/7 – Jennifer Dean. New York Dept of Environmental Conservation. Prioritizing Invasive Species Efforts: Working Smarter with NYS Tools and Data
2/14 – Zion Klos. Marist College. Water and Climate in Social-Ecological Systems: Collaborations in Research, Art, and Science Communication
2/21 – Sonya Auer. Williams College. Energetic Mechanisms for Coping with Environmental Change
2/28 – Seeta Sistla. Hampshire College. Unexpected Impacts of Land-based Solar Arrays: Novel Habitat Heterogeneity Formation and Its Influence on Plant-soil Interactions.
3/7 – Elise McKenna Myers. Columbia University. The Impact of Microbial Particle Association on Pathogen Persistence in the Hudson River Estuary
3/14 – Sarah Mount, ‘10. New York Dept of Environmental Conservation. The Hudson River Eel Project: . Fish Conservation Through Citizen Science
3/21 – SPRING BREAK-NO SEMINAR
3/28 – Leroy Cooper. Vassar College. Inter-relations of Aortic Stiffness, Microvascular Function, and Cardiovascular Disease and Cognition
4/4 – Dorothy Beckett. University of Maryland. Regulating Vitamin Biotin Distribution:. Implications for Health and Biotechnology
4/11 – Swapan Jain. Chemistry Program, Bard College. Regulation of RNA Using Synthetic Small Molecules
4/18 – Brian McGill. University of Maine. Global Change and Biodiversity: Understanding Our Future Through the Past
4/25 – Cathy Collins. Biology Program, Bard College. Title TBD
5/2 – Senior Project talks: Lucy Christiana, Rachael Mendoza, and Melissa Yost-Bido
5/9 – COMPLETION DAYS-NO SEMINAR
Ticks are parasites that ingest blood from their hosts. During their blood meals, they can also ingest microbes, such as bacteria, from their host’s blood, which could influence the microbial community, or “microbiome”, of the tick itself. Using high-throughput sequencing, Felicia Keesing and her colleagues sampled the microbiomes of ticks that had fed on individuals of five different host species — raccoons, Virginia opossums, striped skunks, red squirrels, and gray squirrels. They found that ticks that had fed on different host species had significantly different microbiomes. This is important because some of the microbes that ticks can acquire during their blood meals are pathogens of humans, including the bacterium that causes Lyme disease.
Publication link: https://www.sciencedirect.com/science/article/abs/pii/S1877959X18303297
Full citation: Landesman, W. J., Mulder, K., Allan, B. F., Bashor, L. A., Keesing, F., LoGiudice, K., & Ostfeld, R. S. (2019). Potential effects of blood meal host on bacterial community composition in Ixodes scapularis nymphs. Ticks and tick-borne diseases.
The urban environment is complex and often highly contaminated. This paper from prof. Eli Dueker’s lab takes a close look at how this contamination influences bacteria in urban air. The bacteria present in urban waterways were compared with the bacteria present in urban air, showing that there are many sources for atmospheric bacteria in an urban environment, including sewage contaminated waterways and polluted terrestrial areas. We also observed a ubiquitous distribution of sewage-associated bacteria, in water and air at several urban sites, highlighting the prevalence of of sewage contamination in crowded urban centers and underscoring the complexity of managing this form of pollution in water and air. Surprisingly, we also found that, despite the absence of obvious ecological structures, the air harbored a much more diverse bacterial community than that found in urban waterways. This provides evidence for the possibility of an atmospheric “ecology” and is a step towards understanding the role of megacities in determining the quality of urban air.
Citation: Dueker, M. E., French, S., & O’Mullan, G. D. (2018). Comparison of Bacterial Diversity in Air and Water of a Major Urban Center. Frontiers in Microbiology, 9.
The savannas of East Africa are renowned for their abundant and diverse wildlife. But wildlife populations in this region are declining dramatically, in part because of conflicts with humans and their livestock. Felicia Keesing and her colleagues studied the ecological, economic, and social consequences that arise when livestock and wildlife co-occur versus when the two groups live separately. They found that when livestock, particularly cattle, are kept at moderate densities, they actually improve vegetation quality for wildlife, reduce the abundance of parasites, and provide economic and social benefits to people living in the area.
Keesing discussed the research, and its implications, with Scientific American.