Earthworm system immunity and its modulation by nanoparticles

The particulate nature of nanoparticles (NPs) dictates a preferential interaction with cells of the immune system assigned to recognition and elimination of foreign particulates. Probing safety of nano-objects by defining immune responses of environmental organisms is therefore key to environmental nanosafety. Earthworms represent major immunosafety models representing keystone ecosystem engineers and being in intimate contact with soils ensuring exposure to terrestrial NPs. Innate immunity represents the first line of defence against pathogens in invertebrates and despite extensive description of cell populations involved a dearth of information about the associated molecular components exists. This thesis aimed to use genomics approaches to generate a comprehensive systems immunity description of earthworm prior to exploiting transcriptomics to explore the interaction of NPs and earthworms. A tissue-specific transcriptomic atlas has been established for Eisenia fetida and Eisenia andrei representing six tissues from each species. The resultant comparative transcriptomic resource represented an innate immunity database containing immune-related genes from major immune signalling pathways. To refine the tissue-specific database we generated a de novo genome for E. fetida with high contiguity and completeness. Finally, to enhance insight into the different immune functions of the individual types of coelomocytes we generated transcriptomic datasets from eleocytes, hyaline and granular amoebocytes. The interaction between NPs and the earthworm immune system was then explored by combining the direct introduction of copper oxide NPs with bacterial challenge and following the transcript changes within individual coelomocytes cell populations. This resolved the spatial-temporal impact on the immune system into three distinct phases: direct, systemic and differentiation responses. A complementary soil-based exposure using a range of CuNPs, Silicon-CuNPs and copper ion doses explored the comparative response after soil-based biotransformation. This revealed Si-CuNPs to elicit a negligible response whilst differentially regulated genes under high CuNPs were distinct from equivalent copper ion exposure the pathways impacted intersected substantially.