Mathieu Landry

Université du Québec à Montréal
Ph.D. candidate

Supervisor: Steven Kembel
Patrick M.A. James
Start: 2015-05-01
End: 2018-04-30


Since the development of high-throughput sequencing, the importance of the microbial communities for their host has been assessed repeatedly and for a diverse range of hosts. A significant part of those studies were about human-microbes interactions and have generated a plethora of data about the impacts of microbes residing in the human body. Microbes have been found to have an impact on digestion, immune system development, hormone regulation, and the prevalence of many human diseases. In insects, it has been demonstrated that many insect species derive some benefits from microbial symbionts that aid in digestion, immune response, and intraspecific communication. There is speculation that some microbial symbionts could also play a role in the defense against natural enemies (e.g. parasitoid predators) and the length and severity of outbreaks of some insects. The eastern spruce budworm (SBW), Choristoneura fumiferana, is one of the most destructive forest pests in North America. Populations of the SBW follow an endemic-epidemic cycle of around 30 years. It is during the outbreak part of the cycle that the SBW causes important damage to conifer stands, impacting significantly the Canadian lumber industry. The return to endemic status is caused by a variety of factors, one of which is its variety of natural parasitoid predators. We currently know very little about the microbiome of the SBW and its role in digestion of leaf tissue and its outbreak dynamics. Even more, the insecticide Bt (Bacillus thurigiensis) used to fight the SBW could have its efficiency modulated by the intestinal microbiome of the budworm. Understanding what drives the microbiome composition and its importance for the SBW can only lead to better grasp of pest management and microbial ecology in the context of defoliating insects. Therefore, I propose to work on characterizing the microbiome of the SBW along various environmental gradients to assess which factors determine the composition of its microbial community. I also plan to measure the capacity of the spruce budworm to harbor and retain a stable microbiome during digestion and development with rearing experiments. Samples both from the field and reared will also be analyzed with metagenomic pipelines to assess the functional diversity and importance of the microbiome in the previous two experiments. This project aims to bring a better understanding of the relationship between the SBW, its outbreak dynamics and its microbiome by answering three questions: 1) Which factors drive community assembly of the spruce budworm microbiome? 2) Is the spruce budworm gut microbial community stable over time as the larvae develops and digests leaf tissue? 3) What is the metabolic and functional potential of SBW-associated microbes and how is it affected by bacterial community changes? This project could also eventually lead to the elaboration of new means of pest control or to the improvement of existing ones. Finally, this project will give a better grasp of how ecological will impact the establishment of microbial communities and their survival in lepidopteran defoliating insects.


1- Composition of the Spruce Budworm (Choristoneura fumiferana) Midgut Microbiota as Affected by Rearing Conditions
Mathieu Landry, André M. Comeau, Nicolas Derome, Michel Cusson, Roger C. Levesque