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dc.contributor.advisor Strassmann, Joan E.
dc.contributor.advisor Queller, David C.
dc.creatorBrock, Debra Lynn Adams
dc.date.accessioned 2013-03-08T00:32:59Z
dc.date.available 2013-03-08T00:32:59Z
dc.date.issued 2012
dc.identifier.urihttps://hdl.handle.net/1911/70212
dc.description.abstract Recent work has shown that microorganisms are surprisingly like animals in having sophisticated behaviours such as cooperation, communication, and recognition, as well as many kinds of symbioses. Here we show first that the social amoeba Dictyostelium discoideum has a primitive farming symbiosis that includes dispersal and prudent harvesting of the crop. About one-third of wild-collected clones engage in husbandry of bacteria. Instead of consuming all bacteria in their patch, they stop feeding early and incorporate bacteria into their fruiting bodies. They then carry bacteria during spore dispersal and can seed a new food crop, which is a major advantage if edible bacteria are lacking at the new site. However, if they arrive at sites already containing appropriate bacteria, the costs of early feeding cessation are not compensated, which may account for the dichotomous nature of this farming symbiosis. We also observed farmer Dictyostelium discoideum clones carry bacteria that they do not use as food. We hypothesized that these bacteria may play a defensive role against other D. discoideum clones. In our second study, we investigated the impact of these bacteria-carrying farmers on non-farming D. discoideum clones. We found that the presence of farming clones reduces spore production in non-farmers. Furthermore, this effect increases with frequency of farming clones, demonstrating the vulnerability of non-farming clones to farmers though in this experiment we had not separated the effects of the farmer clone and the bacteria they carry. In our third study we exposed non-farmers to a filtered supernatant from the most common non-food carried bacterium, Burkholderia xenovorans . This supernatant is likely to carry whatever the bacteria are producing. We treated Dictyostelium clones at the beginning of the social stage and found that the supernatant enhanced spore production of farming clones and hurt spore production of non-farming clones. This study shows that the effects of the bacteria can be restricted to a filtered supernatant alone. This discovery of symbiosis of D. discoideum with bacteria, and its impact on social interactions among D. discoideum clones will provide a fertile ground for further experiments on the evolution of sociality.
dc.format.extent 114 p.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subjectBiological sciences
Social amoeba
Dictyostelium discoideum
Farming symbiosis
Burkholderia xenovorans
Microbiology
Evolution & development
dc.title Evolutionary costs and benefits of a newly discovered symbiosis between the social amoeba Dictyostelium and bacteria
dc.identifier.digital BrockD
dc.type.genre Thesis
dc.type.material Text
thesis.degree.department Ecology and Evolutionary Biology
thesis.degree.discipline Natural Sciences
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy
dc.identifier.citation Brock, Debra Lynn Adams. "Evolutionary costs and benefits of a newly discovered symbiosis between the social amoeba Dictyostelium and bacteria." (2012) Diss., Rice University. https://hdl.handle.net/1911/70212.


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