A new review paper from Felicia Keesing explores how diversity can affect disease transmission. For many diseases of plants and animals, including humans, the presence of low-quality hosts reduces the overall transmission of disease-causing parasites. People have used these “dilution effects” to manage diseases for over a century. More recent evidence demonstrates that dilution effects also occur naturally, protecting us from greater risk of being exposed to infectious diseases. When biodiversity declines, these natural dilution effects disappear, providing a powerful link between the conservation of biodiversity and the health of humans, wildlife, and plants.
Publication info: Keesing, F., & Ostfeld, R. S. (2021). Dilution effects in disease ecology. Ecology Letters.
There were lots of exciting news in the Keesing Lab in 2020. Professor Felicia Keesing coauthored a whole sequence of papers, including “Species that can make us ill thrive in human habitats” that was published in Nature; “Spatial and temporal patterns of the emerging tick-borne pathogen Borrelia miyamotoi in blacklegged ticks (Ixodes scapularis) in New York” in a journal “Parasites & Vectors”, and a paper “A new genetic approach to distinguish strains of Anaplasma phagocytophilum that appear not to cause human disease,” in a journal named Ticks and Tick-borne Diseases.
In September 2020 professor Keesing was also the featured
scientist on BBC One documentary “Extinction: The Facts with David Attenborough”. Her statements as an expert were included in articles published in The Guardian, The Scientist, Smithsonian Magazine, Canada’s National Observer, and Inside Higher Ed.
Links to press-releases:
Several new genome sequences of Bacillus subtilis and Bacillus velezensis strains were published by the Perron lab. These beneficial bacteria are important for making of many traditional fermented foods, and these strains in particular were isolated from samples of Kimchee cabbage.
Two Perron lab alums, Tejaswee Neupane, and Rachael Mendoza, are coauthors on this paper, as most of the work was done by them as a part of their senior projects!
Full text: https://mra.asm.org/content/ga/9/23/e00085-20.full.pdf
Citation: Perron, G. G., Neupane, T., & Mendoza, R. A. (2020). Draft Genome Sequences of Bacillus subtilis Strains TNC1 (2019), TNC3 (2019), and TNW1 (2019), as Well as Bacillus velezensis Strains TNC2 (2019) and TNW2 (2019), Isolated from Cabbage Kimchee. Microbiology Resource Announcements, 9(23).
Image source: WIkipedia
Migratory birds facing a number of hazards during their journeys. Collisions with buildings have become a major conservation problem for them, but the exact reason why so many birds collide with buildings is unclear. Several studies suggest that birds are attracted to nighttime building lighting. Bruce Robertson helped discover a new kind of light pollution, polarized light pollution, that could also be responsible. The light that reflects from glass buildings gets polarized, which may cause it to look like a water body at a distance, instead of a large dangerous object approaching fast. This collaboration between Bruce Robertson at Bard College and Sirena Lao and Scott Loss at the University of Oklahoma asked whether polarized, or unpolarized light pollution was more strongly associated with bird collisions with buildings in downtown Minneapolis. We found that birds were most likely to collide with individual windows that were lit at night, but that there was little evidence that polarized light pollution was attracting birds. This suggests that turning out the lights in each room of office buildings can help migratory birds avoid collisions.
Lao, S., Robertson, B.A., Anderson, A.W., Blair, R.B., Eckles, J.W., Turner, R.J. and Loss, S.R., 2020. The influence of artificial night at night and polarized light on bird-building collisions. Biological Conservation, 241, p.108358.
Biology professor Felicia Keesing and her colleagues published a paper in Scientific Reports that describes a mathematical model that can be used to manage livestock on grazing lands around the world. While previous models to manage livestock grazing exist, they require a lot of data and those data are hard to collect, making the models less useful. Keesing’s team developed a model that requires very little data yet makes sophisticated predictions, including estimating how much grass would be left over to support wild grazers. The model successfully predicted grass abundance at the team’s field sites in Kenya.
A new paper from the Khakhalin lab:
Intrinsic temporal tuning of neurons in the optic tectum is shaped by multisensory experience
Silas E. Busch and Arseny S. Khakhalin
5 SEP 2019 https://doi.org/10.1152/jn.00099.2019
(The published version is behind a paywall, but you can find a free version here: https://www.biorxiv.org/content/10.1101/540898v2)
In his senior project, which eventually became the foundation for the paper, Silas Busch ’16 asked whether different neurons in the optic tectum of Xenopus tadpoles are tuned to inputs of different duration. Now, there’s lots to unpack in this sentence! So let’s talk about it bit by bit. Silas worked with tadpoles: the larvae of Xenopus frogs (you might have seen these frogs: they look a bit like underwater rubber toys, and are popular as pets). Even though tadpoles are small, they still have a brain, and in this brain, they have a part called “the optic tectum”. This brain area helps tadpoles to navigate in the water. As everything else in the body, the brain is made of cells, and these cells, called neurons, are connected to each other in some meaningful fashion that, frankly, we still don’t completely understand. Neurons send electrochemical impulses to each other, and it is this dance of activation in the tectum that allows tadpoles to swim without running head-first into walls or other tadpoles.
The question that Silas asked in his paper, is whether tectal neurons are different from each other in one very specific way. He looked at whether they all respond similarly to fast and slow patterns of activation, arriving from other neurons, or whether some of them have a preference for either fast or slow activation profiles. Say, if a neuron receives signals from 3 other neurons at the same time, will it respond to them in the same way as it would respond if these signals were a tiny bit staggered? To answer this question, Silas used a fancy technique called the “Dynamic clamp” that allowed him to connect to neurons one by one with a tiny glass electrode, and then control electrical currents in each neuron with a computer, simulating different patterns of activation.
What Silas found is that most tectal neurons do have a preference for either short or long (synchronous or asynchronous) patterns of activation, and that this preference changes depending on what tadpoles see and hear. It means that the tadpole brain as a whole, and each individual neuron in this brain on its own, adjust to changes in the world around the animal; presumably, to give the tadpole an ability to better navigate and survive. This particular type of neuron-by-neuron temporal tuning was not described in the tectum before, and also nobody yet used the dynamic clamp technique to look for tuning of this type. We don’t yet know exactly what these findings could mean for our understanding of the brain, but it is very exciting to learn that there is one more aspect to brain develpoment, that was so far somewhat overlooked!
It is also curious to think that this paper would not have happened if Silas hadn’t returned to the lab to work for 4 extra days immediately after graduation, on a Sunday after his commencement ceremony! In April 2016, as he was writing his senior project, Silas realized that some of the data he recorded could not be used. Even though he was obviously tired, and excited to graduate and leave Bard, Silas still decided to spend four more (!) full days in a lab without windows (our lab just happens to not have windows), to finish the work. It is not that often that you can point at one seemingly minor decision and realize that it was a key for success, but for this paper, it is really true. Without these four extra days of work, we would not have had enough data, and this paper would have never happened.
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.
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.