Gregarine apicomplexans – a useful experimental model? Our limited knowledge regarding gregarines is in a large part due to the lack of available culturing techniques. Currently, there are no in vitro culture methods to culture gregarines in a laboratory environment. The current culture methods are limited to the culturing of the host organisms, which can be restricted due to seasonality (for collection of hosts), costs (to maintain complex host life cycles) and labour-intensiveness (for regular feeding, cleaning and maintenance of host culture systems). In a Gordon & Betty Moore Foundation funded project co- ordinated by Edinburgh Napier University, UK, with partners at the University of Kent, UK, the University of Rhode Island, USA, and the Institute of Parasitology at the Biology Centre CAS, Czech Republic, we are working on the development of an in vitro culture platform for gregarines. The ability to culture gregarines in a laboratory environment would allow a consistent and host-free supply of gregarine material. This in turn would enable the scientific community to not only generate transcriptomic and genomic data more easily but utilise the gregarines in in situ environments to explore their biological functions (using -omics) and symbiotic roles. The latter could be achieved by integrating novel microfluidic devices along with specialised polymers; these technologies have been used in the past to investigate microbiome–host interactions in humans and other animals.
parasitic lifestyle need further exploration. Gregarines are early branching Apicomplexa potentially having undergone extraordinary radiation along with their marine and terrestrial hosts. So far, molecular information in gregarines has mainly been used to differentiate species and describe their phylogenetic relationships. Studies over the past decades have provided evidence of a remnant plastid (small organelles usually found in photosynthetic organisms), the so-called ‘apicoplast’, in many apicomplexan species. The presence of this organelle in gregarines has been proven with molecular techniques only recently, adding to the evidence of a common photosynthetic origin. These findings support the loss of photosynthesis in the evolutionary path of gregarines in the transition to a symbiotic lifestyle. This evolutionary process has happened multiple times resulting in multiple lineages of similar symbionts. Some gregarines, likewise with Cryptosporidium , seem to have lost the apicoplast, which is essential to many other Apicomplexa. It is important to understand how gregarines and other closely related organisms have coped with the complete loss of the apicoplast, and how their metabolic and cellular machinery has adapted over evolutionary time. While recent transcriptomic and genomic studies have provided the first ideas about these transitions, the use of genetic and cell biological techniques in organisms across the symbiotic spectrum will provide the answer to our questions.
Mattesia
Gregarina
Selenidium
Siedleckia
Babesia
Theileria
Plasmodium
Cryptosporidium
Nephromyces
Toxoplasma Eimeria
Simplified phylogeny of the phylum Apicomplexa with the various host organisms added. Emma Betts
90 Microbiology Today October 2022 | microbiologysociety.org
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