Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - STEPN-UP (Stilbene and entomopathogenic nematodes: Unlocking the potential)
Teaser
Bacteria frequently form intimate associations with a eukaryotic host where they may have critical roles in the development, behavior, and/or functions of their animal symbiont. While the underlying molecular mechanisms are poorly understood there is increasing evidence that...
Summary
Bacteria frequently form intimate associations with a eukaryotic host where they may have critical roles in the development, behavior, and/or functions of their animal symbiont. While the underlying molecular mechanisms are poorly understood there is increasing evidence that the bacteria are sending signals to their host. The goal of this project was to understand the inter-kingdom signaling that occurs between a bacterium and its animal host using, as a model, the interaction between an entomopathogenic nematode (EPN) called Heterorhabditis and its symbiotic bacterium, Photorhabdus. The Heterorhabditis-Photorhabdus EPN complex has been exploited as a biological control agent for >20 years and various product formulations are currently available in the EU. Although the global biocontrol market (currently estimated at €200 million per annum) has seen significant market growth over the past 5-10 years the market for EPNs has been relatively flat . This stagnation is due in part to the relatively high costs associated with the production and storage of the product. The STEPN-UP project aimed to generate new knowledge on the Heterorhabditis-Photorhabdus EPN complex in order to enable future rationale-based approaches to improve EPN production for commercial exploitation to benefit the agri-food sector and the environment/society.
EPNs are soil-dwelling organisms that utilize a bacterial symbiont to kill their insect targets . Photorhabdus plays a key role in the EPN life-cycle and is required to have 3 distinct functions during the life-cycle of the EPN complex: 1) Photorhbdus must kill the insect host; 2) Photorhabdus must convert the insect cadaver into a nutrient soup for nematode growth and development and 3) Photorhabdus must re-colonise a specialized free-living stage of the nematode (the infective juvenile) that emerges from the dead insect to find a new host . A key metabolite produced by the bacteria during this complex life-cycle is called ST and, importantly, ST is required for nematode growth and development.
Therefore, the overall research objectives for STEPN-UP as listed in the application are:
1) to investigate the evolutionary history of ST synthesis proteins.
2) to determine the nematode response to ST.
3) to engineer the bacteria to produce increased levels of ST.
Briefly this project showed that:
1) Proteins involved in the production of ST are unique in Photorhabdus.
2) The alarmone (p)ppGpp is essential for the full reproductive potential of the nematode.
3) The Cpx regulon in Photorhabdus is necessary to maintain its symbiotic relationship with Heterorhabditis.
Work performed
During this project we wanted to better understand the interaction between the bacteria and the nematode. Using a variety of molecular techniques we have :
1. shown that Photorhabdus has evolved unique activities (e.g. stilbene production) that are essential for the interaction with the nematode.
2. identified some genes that may be over-expressed in the monoxenic nematodes and these genes will be validated before further analyses.
3. shown that the bacteria has a complex role in controlling nematode growth and development.
4. identified a signaling pathway in Photorhabdus that is required for colonization of the nematode.This may enable future studies aimed at improving colonization of the IJ and, therefore, improved EPN performance.
Dissemination
Presentations
a) Seminar at APC Microbiome Ireland Marie Curie workshop where I presented my career progression, the goal of my project, and my research findings.
b) Oral presentation (The effect of Photorhabdus (p)ppGpp on Heterorhabditis growth and development) at the 2018 meeting of the European Society of Nematologists in Ghent, Belgium (September 9-13, 2018)
c) Oral presentation at the UMR DGIMI lab at Université de Montpellier, France (June 6-8, 2018).
Publications
1 paper that is currently undergoing peer review at an Open Access journal and 2 manuscriptis in preparation.
Public Engagment
a) The fellow participated in two workshops with secondary school students, UCC Plus Xperience Camp and a Budding Biologist workshop. We taught students with hands-on demonstrations about digestion, the microbiome, taste, and DNA extraction. Both workshops included opportunities to share my job and research project with these students. (June 7, 2017 and November 16, 2017)
b) The fellow attended the Irish National Ploughing Championship where we shared science with children and adults including the President of Ireland Michael D. Higgins. (September 18, 2018)
c) The fellow participated in a Women’s Day outreach to display the work in which women scientists can accomplish. (March 8, 2018)
Data was shared with our non-academic partner (e-nema GmbH) but this project has not generated results that could have been exploited for industrial purposes.
Final results
This work has increased our understanding of EPNs, which will feed into future projects aimed at developing this green technology. We have described a new bacterial regulatory network that is important during the interaction with the nematode. Moreover we have, for the first time, identified genes in the nematode that may be involved in the interaction with the bacterial symbiont. This preliminary knowledge provides numerous areas that can be further explored to understand and produce a stronger symbiotic relationship.