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Developing gregarine apicomplexans as aquatic symbiosis model system

School of Applied Sciences

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Dr S Rueckert , Dr A Tsaousis No more applications being accepted Funded PhD Project (Students Worldwide)

About the Project

The Gordon and Betty Moore Foundation’s Symbiosis in Aquatic Systems Initiative, seeks to advance the understanding of aquatic symbioses that include microbial partners.

Being part of this initiative we are able to provide a great opportunity for a PhD student to join our international project. This PhD project is based within the School of Applied Sciences at Edinburgh Napier University and is led by Dr Sonja Rueckert
( and Dr Anastasios Tsaousis

Apicomplexans are widely distributed, single-celled organisms that are always described as obligate parasitic. Despite their importance for human health (malaria, toxoplasmosis) and their virulence in animals, there is substantial evidence for mutualistic attributes of some apicomplexans (Rueckert et al. 2019; Paight et al., 2018). Gregarine apicomplexans infect almost all invertebrates and are highly abundant across ecosystems (Rueckert et al. 2011; de Vargas et al. 2015; Cleary & Durbin 2016; Lentendu et al. 2018). The early diverging gregarines span the whole range of symbiosis from mutualism to parasitism (Rueckert et al. 2019) and thus are critical links in the evolution of symbiosis in the apicomplexans. Despite their importance, information on the biology and evolution of these organisms is lacking with e.g. only a handful of transcriptome and genome data available (Mathur et al. 2019, Janouškovec et al. 2019).

In-vitro culturing has not been achieved for any gregarine, thus this PhD project aims to develop gregarines as model system. This model system will enable us to advance the fundamental knowledge on the evolutionary steps of symbiosis in the Apicomplexa, identifying key cellular and molecular transitions in the evolution from free-living relatives to intracellular parasites.

The aim of this project is to develop culturing steps towards an axenic, tissue free system:
1) Develop invertebrate in-vitro culture
The student will develop and maintain in-vitro culturing systems for gregarines, using their aquatic invertebrate hosts (e.g. polychaetes, sea squirts, arthropods). The host’s microbiome and metagenome will be characterized, and associated metabolic profiles obtained. Gregarine transcriptome, genome and cell biology data for selected systems will be produced to gain a holistic picture of the gregarine-host-microbiome interactions.

2) Develop invertebrate in-vitro tissue culture
The PhD student will establish an invertebrate in-vitro 2D tissue culture for gregarine apicomplexans. They will develop invertebrate cell cultures using tissues from the gut of invertebrate hosts employed in step-1. This approach will be assessed by infecting the host cells with the target species and monitor the success of gregarine development and propagation using an in-house automated microscopy system, under controlled atmospheric conditions.

Academic qualifications
A first degree (at least a 2.1) ideally in a relevant field such as marine parasitology, protistology, or microbiology, molecular biology with a good fundamental knowledge of microbial eukaryotes, cell biology and laboratory skills.

English language requirement
IELTS score must be at least 6.5 (with not less than 6.0 in each of the four components). Other, equivalent qualifications will be accepted. Full details of the University’s policy are available online.

Essential attributes:
• Experience of fundamental laboratory skills
• Competent in aseptic techniques
• Knowledge of bioinformatics
• Good written and oral communication skills
• Strong motivation, with evidence of independent research skills relevant to the project
• Good time management

Desirable attributes:
• Good fundamental knowledge and strong interest in culturing invertebrates and/or micro-eukaryotes
• Laboratory skills including invertebrate dissections, microscopy, parasite isolation and identification, molecular techniques
• Competent in data anlysis, phylogenetics and establishing genome and transcriptome data
• Image processing

Please quote the project code SAS0068 in your enquiry and application.

Funding Notes

Fully funded position (Home/EU level full-time fees, plus monthly stipend payments at the prevailing rate set by the Research Councils for three academic years. Envisioned starting date is October 2020, subject to COVID-19 guidance/recommendations.

Application form
2 academic references, using the Postgraduate Educational Reference Form (Found on the application process page)
A personal research statement (Including a) a brief description of relevant experience/skills, b) an indication of what you would uniquely bring to the project and c) a statement of how this project fits with your future direction.)
Evidence of proficiency in English (if appropriate).


Cleary & Durbin (2016) Unexpected prevalence of parasite 18S rDNA sequences in winter among Antarctic marine protists. J. Plankton Res., 38(3):401-417
De Vargas et al. (2015) Ocean plankton. Eukaryotic plankton diversity in the sunlit ocean. Science, 348: 1261605
Janouškovec et al. (2019) Apicomplexan-like parasites are polyphyletic and widely but selectively dependent on cryptic plastid organelles. eLife, 8: e49662
Lentendu et al. (2018) Consistent patterns of high alpha and low beta diversity in tropical parasitic and free-living protists. Mol. Ecol., 27(13): 2846-2857
Mathur et al. (2019) Multiple independent origins of apicomplexan-like parasites. Curr. Biol., 29: 2936-2941.e5
Paight et al. (2019) Nephromyces encodes a urate metabolism pathway and predicted peroxisomes, demonstrating that these are not ancient losses of Apicomplexans. Genome Biol. Evol., 11(1): 41-53
Rueckert & Horák (2017) Archigregarines of the English Channel revisited: new molecular data on Selenidium species including early described and new species and the uncertainties of phylogenetic relationships. PLoS One, 12: e0187430
Rueckert et al. (2011) Identification of a divergent environmental DNA sequence clade using the phylogeny of gregarine parasites (Apicomplexa) from crustacean hosts. PLoS One, 6: e18163
Rueckert et al. (2019) The symbiotic spectrum: Where do the gregarines fit? Trends Parasitol., 35: 687-694
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