About this Research Topic
The 1.5 billion year-long evolution of eukaryotes proceeded in close association with bacteria and archaea. The very origin of this group, as it is currently viewed, was due to the formation of an endosymbiotic relationship with an α-proteobacterium, which later become the mitochondrion. Another pivotal moment in the evolution of eukaryotes and the entire biosphere was the acquisition of intracellular symbionts of cyanobacterial origin, resulting in the rise of algae and, subsequently, macroscopic plants.
Numerous symbiotic associations of bacteria and/or archaea with plants and animals have been intensely studied for a long time, since many of these are of practical importance, especially when this concerns antagonistic relationships (those, where the microbial symbiont is parasitic). Much less attention has been paid to the symbioses of bacteria /archaea with protists, therefore the knowledge about these relationships is rather scarce and unevenly distributed among various protist taxa. Meanwhile, single-celled eukaryotes can represent good models for studying this phenomenon, not to mention the fascinating diversity of such associations in nature.
Some protists may host entire consortia of microorganisms, as exemplified by the giant amoeba Pelomyxa palustris processing sapropel with the help of one archaeal and two bacterial endosymbionts, or the termite gut-inhabiting parabasalian Trichonympha spp., combining bacterial endo- and ectosymbionts in order to feed on wood particles. These relationships may range from transient facultative associations, such as those between Acanthamoeba spp. and various bacteria, to finely-tuned (as a result of a long-term coevolution) obligate systems observed in trypanosomatids of the subfamily Strigomonadinae. Although in many cases it is difficult to understand the exact nature of the relationships between protists and their bacterial and/or archaeal cohabitants, there are examples of mutualism (Phycorickettsia spp. in eustigmatophyte algae) and parasitism (Holospora spp. in Paramecium spp.). Some symbioses may even be of medical importance, when a protist carries bacteria pathogenic to humans, e.g., Mycoplasma hominis in Trichomonas vaginalis or Vibrio cholera, Listeria monocytogenes, Escherichia coli etc. in the abovementioned acanthamoebae.
This Research Topic is proposed to cover all aspects of ecto- and endosymbioses between protists and bacteria/archaea including, but not being restricted to the following ones:
• Diversity and ecology of symbiotic associations between protists and bacteria/archaea
• Genomics of the organisms involved in these symbioses
• Metabolic interactions between the partners and cellular dynamics of host-symbiont relationships
• Evolution of symbioses between protists and bacteria/archaea, including studies employing unicellular eukaryotes as a model of early evolution of organelles
We welcome researchers to submit their manuscripts on the topic in the form of Original Research, Opinion, or Review articles.
Keywords: metabolism, ecology, organelle evolution, symbionts in protists, genomics
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