The establishment of symbioses between eukaryotic hosts and bacterial symbionts in nature is a dynamic process. The formation of such relationships depends on the life history of both partners. Bacterial symbionts of amoebae may have unique evolutionary trajectories to the symbiont lifestyle, because bacteria are typically ingested as prey. To persist after ingestion, bacteria must first survive phagocytosis. In the social amoeba
Anaerobiosis has independently evolved in multiple lineages of ciliates, allowing them to colonize a variety of anoxic and oxygen‐depleted habitats. Anaerobic ciliates commonly form symbiotic relationships with various prokaryotes, including methanogenic archaea and members of several bacterial groups. The hypothesized functions of these ecto‐ and endosymbionts include the symbiont utilizing the ciliate's fermentative end products to increase the host's anaerobic metabolic efficiency, or the symbiont directly providing the host with energy by denitrification or photosynthesis. The host, in turn, may protect the symbiont from competition, the environment, and predation. Despite rapid advances in sampling, molecular, and microscopy methods, as well as the associated broadening of the known diversity of anaerobic ciliates, many aspects of these ciliate symbioses, including host specificity and coevolution, remain largely unexplored. Nevertheless, with the number of comparative genomic and transcriptomic analyses targeting anaerobic ciliates and their symbionts on the rise, insights into the nature of these symbioses and the evolution of the ciliate transition to obligate anaerobiosis continue to deepen. This review summarizes the current body of knowledge regarding the complex nature of symbioses in anaerobic ciliates, the diversity of these symbionts, their role in the evolution of ciliate anaerobiosis and their significance in ecosystem‐level processes.
more » « less- NSF-PAR ID:
- 10378154
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Eukaryotic Microbiology
- Volume:
- 69
- Issue:
- 5
- ISSN:
- 1066-5234
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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