03.02.2015
Doctoral Dissertation

6.2. M.Sc. Lauri Mikonranta (Faculty of Mathematics and Science, Ecology and Evolutionary Biology)

Time:

6.2.2015 12:00 — 15:00


Location: Ylistonrinne , YAA303
M.Sc. Lauri Mikonranta defends his doctoral dissertation in Ecology and Evolutionary Biology ”Virulence evolution and immune defence: Pathogen-host interactions between an environmentally transmitted bacterium Serratia marcescens and its insect hosts”. Opponent Professor Michael T. Siva-Jothy (University of Sheffield) and custos Professor Johanna Mappes (University of Jyväskylä).

Photo by Jyrki Torniainen.M.Sc. Lauri Mikonranta defends his doctoral dissertation in Ecology and Evolutionary Biology ”Virulence evolution and immune defence: Pathogen-host interactions between an environmentally transmitted bacterium Serratia marcescens and its insect hosts”. Opponent Professor Michael T. Siva-Jothy (University of Sheffield) and custos Professor Johanna Mappes (University of Jyväskylä).

The event is in English.

Pathogens are one of the most significant factors limiting population sizes in the wild and major drivers of the evolution of their hosts. Similarly, the antagonistic interactions keep obligatory pathogens co-evolving with their host defences. In opportunistic pathogens that are able to proliferate outside their hosts, the life cycle is however non-dependent from direct host-to-host transmission and more exposed to the outside-hosts environment. In this thesis, factors that affect the successfulness of opportunistic bacterial infection in insects are examined from both pathogens’ and hosts’ perspectives. Evolutionary experiments reveal that virulence of the entomopathogenic bacterium Serratia marcescens is shaped by the interplay of selection pressures in a non-host environment and within hosts. Results show that anti-predatory adaptation outside the host can directly trade off with bacterial virulence traits. Even in a setting where the pathogen is let to evolve within the host, minimizing the between-hosts selection, increased virulence is not necessarily the best strategy for pathogen fitness. Results on host defence show that the insect innate immunity has an acquired aspect where infection with a previously encountered pathogen can be diminished without the antibody-based immune memory akin to vertebrates. Further, Lepidopteran hosts are able to adjust their immunity related gene expression accordingly to the infecting pathogen strain. Together these findings can have implications on epidemiological consequences of host-parasite co-evolution, management of environmentally transmitted opportunistic pathogens, and biological control of insect pests.

The dissertation is published in the series  Jyväskylä Studies in Biological and Environmental Science, no 298, 109 p., Jyväskylä 2015. ISSN 1456-9701;298, ISBN 978-951-39-6071-1. It is available at the University Library’s Publications Unit, +358 (0)40 805 3825, myynti@library.jyu.fi.

More information

Lauri Mikonranta

Doctoral Student

None

lauri.mikonranta@jyu.fi