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Abstract Bacterial endosymbionts can provide benefits for their eukaryotic hosts, but it is often unclear if endosymbionts benefit from these relationships. The social amoeba Dictyostelium discoideum associates with three species of Paraburkholderia endosymbionts, including P. agricolaris and P. hayleyella. These endosymbionts can be costly to the host but are beneficial in certain contexts because they allow D. discoideum to carry prey bacteria through the dispersal stage. In experiments where no other species are present, P. hayleyella benefits from D. discoideum while P. agricolaris does not. However, the presence of other species may influence this symbiosis. We tested if P. agricolaris and P. hayleyella benefit from D. discoideum in the context of resource competition with Klebsiella pneumoniae, the typical laboratory prey of D. discoideum. Without D. discoideum, K. pneumoniae depressed the growth of both Paraburkholderia symbionts, consistent with competition. P. hayleyella was more harmed by interspecific competition than P. agricolaris. We found that P. hayleyella was rescued from competition by D. discoideum, while P. agricolaris was not. This may be because P. hayleyella is more specialized as an endosymbiont; it has a highly reduced genome compared to P. agricolaris and may have lost genes relevant for resource competition outside of its host.
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Fitness costs and benefits vary for two facultative Burkholderia symbionts of the social amoeba, Dictyostelium discoideum
Abstract Hosts and their associated microbes can enter into different relationships, which can range from mutualism, where both partners benefit, to exploitation, where one partner benefits at the expense of the other. Many host–microbe relationships have been presumed to be mutualistic, but frequently only benefits to the host, and not the microbial symbiont, have been considered. Here, we address this issue by looking at the effect of host association on the fitness of two facultative members of theDictyostelium discoideummicrobiome (Burkholderia agricolarisandBurkholderia hayleyella). Using two indicators of bacterial fitness, growth rate and abundance, we determined the effect ofD. discoideumonBurkholderiafitness. In liquid culture, we found thatD. discoideumamoebas lowered the growth rate of bothBurkholderiaspecies. In soil microcosms, we tracked the abundance ofBurkholderiagrown with and withoutD. discoideumover a month and found thatB. hayleyellahad larger populations when associating withD. discoideumwhileB. agricolariswas not significantly affected. Overall, we find that bothB. agricolarisandB. hayleyellapay a cost to associate withD. discoideum, butB. hayleyellacan also benefit under some conditions. Understanding how fitness varies in facultative symbionts will help us understand the persistence of host–symbiont relationships. OPEN RESEARCH BADGESThis article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available athttps://openscholarship.wustl.edu/data/15/
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- PAR ID:
- 10372489
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 9
- Issue:
- 17
- ISSN:
- 2045-7758
- Page Range / eLocation ID:
- p. 9878-9890
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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