I am an environmental microbiologist who applies molecular techniques to study how microbial communities – that is, the assembly of bacteria, fungi and other microscopic organisms – affect ecosystem processes of importance to humanity. I maintain two major areas of research: a) the microbial ecology of tick-borne diseases and b) the biogeography of soil microbial communities. My research is carried out in collaboration with a team of undergraduate researchers at Green Mountain college and I mentor students in the Masters of Science in Environmental Studies program. If you are interested in joining my lab, feel free to drop me a line.
The microbial ecology of Lyme disease
For the past four years I have been funded by the Vermont Genetics Network to study environmental and microbiological factors that influence how Lyme disease risk varies across forested ecosystems of Rutland County, Vermont. My research lab of undergraduate students and I perform annual measurements of tick densities in several local forests and test these ticks for infection with Borrelia burgdorferi, the spirochete bacterium that causes Lyme disease. Additionally, we characterize the biodiversity and species composition of bacteria inhabiting the ticks. We are testing the hypothesis that the particular assembly of microbial species inhabiting a tick (the “tick microbiome”) affects the likelihood that the tick will maintain an infection that can be passed on to other animals, including humans.
Biogeography of soil microbial communities
I study how the composition of soil bacterial communities change over time and space in response to environmental conditions. In a recent study I used high throughput DNA sequencing to characterize bacterial communities in twelve forest ecosystems in the eastern United States. I found that bacterial communities are highly sensitive to changes in soil pH and often by the composition of nearby tree species as well. At the same time, I found that different tree species are often associated with distinct soil pH. Therefore, it is likely that tree species are indirectly influencing the composition of soil bacterial communities in their immediate surroundings by altering the soil pH (for example, through inputs of organic matter and differences in how they cycle nutrients) of their environment.
Landesman, W.J., Mulder, K., Allan, B., Bashor, L., Keesing, F., LoGiudice, K. and Ostfeld, R. 2019. Potential effects of blood meal host on bacterial community composition in Ixodes scapularis nymphs. In press at Ticks and Tick-Borne Diseases.
Landesman, W.J., Freedman, Z. and Nelson, D. 2019. Seasonal, sub-seasonal and diurnal variation of soil bacterial community composition in a temperate deciduous forest. In press at FEMS Microbiology Ecology.
Landesman, W.J. , D. Nelson and M. Fitzpatrick. 2014. Influence of soil properties, tree species and geographic distance on ß-diversity of soil bacterial communities. Soil Biology and Biochemistry 76: 201-209.
Landesman, W.J. and J. Dighton. 2011. Shifts in microbial biomass and the bacteria:fungi ratio occur under field conditions within three hours after rainfall. Microbial ecology 62(1): 228-236.
Landesman, W.J., Amy M. Treonis, and John Dighton. 2011. Effects of a one-year rainfall manipulation on soil nematode abundances and community composition. Pedobiologia 54(2): 87-91.
Landesman, W. J. and J. Dighton. 2010. Response of soil microbial communities and the production of plant-available nitrogen to a two-year rainfall manipulation in the New Jersey Pinelands. Soil Biology and Biochemistry 42: 1751-1758.
Allan, B.F., R.B. Langerhans, W.A. Ryberg, W.J. Landesman, N.W. Griffin, R.S. Katz, B.J. Oberle, M.R. Schutzenhofer, K.N. Smyth, A. de St. Maurice, L. Clark, K.R. Crooks, D.E. Hernandez, R.G. McLean, R.S. Ostfeld and J.M. Chase. 2009. Ecological correlates of risk and incidence of West Nile virus in the United States. Oecologia 158: 699–708.
Landesman, W.J., B.F. Allan, R.B. Langerhans, T.M. Knight and J.M. Chase. 2007. Inter-annual associations between precipitation and human incidence of West Nile Virus in the United States. Vector-Borne and Zoonotic Diseases 7(3): 337-343.
Learn more about my research from these newspaper, radio and television interviews
Useful links for more information on Lyme disease
Biology I: Ecology (BIO 1031)
This is the first course you will take as a Biology major at Green Mountain College. Ecology is the scientific study of the biotic and abiotic factors that determine the abundance and distribution of species. During this course we explore ecology at four fundamental levels of organization: organisms, populations, communities and ecosystems. During laboratories you will learn how to collect and analyze ecological data in the field and in the laboratory. You will learn how to communicate your findings in the format of a scientific paper and oral presentations.
Soil Ecology (BIO 4005)
During soil ecology we explore the how some of the smallest organisms, hidden away in the tiniest cracks and crevices of the earth, play such a central role in many ecosystem processes of importance to humanity. A large portion of the course is dedicated to the study of soil microbes (including bacteria, archaea, fungi, protozoa and viruses) and ecosystem functions they perform. For example, you will learn how soil microbes contribute to the natural fertility of organic farms and how they impact the global climate by sequestering and releasing greenhouse gases. In addition, we will study interactions between microbes and mesofauna and macrofauna including nematodes, microarthropods and earthworms. You will gain hands-on field experience collecting soil samples, analyzing their physical and biological properties and learning how microbial communities are studied using molecular biological techniques. You will learn how to analyze and critically evaluate papers from the peer-reviewed literature and popular media.
Photo: Soil nematodes from the New Jersey Pinelands that were studied during one part of my dissertation research. These microscopic worms play an important role in plant health and soil fertility. Clockwise from top left: Aphelenchoididae (fungal feeder), Cephalobidae and Primatolaimidae (bacterial feeders), Criconematidae (plant parasite), Dorylaim (omnivore).
Microbiology (BIO 4008)
Microbiology is the study of the characteristics and functions of the smallest organisms on earth. The vast majority of species are microbial and their impact on climate, ecosystems and humanity are immense. This is a great time to study microbiology. Using a variety of new laboratory and analytical approaches, microbiologists are discovering an extraordinary number of new species and metabolic processes carried out by microbes. Our new understanding of the interdependence of microbes and many multi-cellular organisms, including humans, is literally re-writing our understanding of biology itself. During this class we will focus primarily on the prokaryotes (bacteria and archaea) – their cell structure, metabolism, growth, behavior, pathogenesis and genetics. In addition, we will survey the viruses and fungi, especially with respect to the many ways in which they benefit and harm human society.