Analysis.R from Symbiotic bacteria, immune-like sentinel cells, and the response to pathogens in a social amoeba

Some endosymbionts living within a host must modulate their hosts' immune systems in order to infect and persist. We studied the effect of a bacterial endosymbiont on a facultatively multicellular social amoeba host. Aggregates of the amoeba <i>Dictyostelium discoideum</i> contain a subpopulation of sentinel cells that function akin to the immune systems of more conventional multicellular organisms. Sentinel cells sequester and discard toxins from <i>D. discoideum</i> aggregates and may play a central role in defense against pathogens. We measured the number and functionality of sentinel cells in aggregates of <i>D. discoideum</i> infected by bacterial endosymbionts in the genus <i>Paraburkholderia</i>. Infected <i>D. discoideum</i> produced fewer and less functional sentinel cells, suggesting that <i>Paraburkholderia</i> may interfere with its host's immune system. Despite impaired sentinel cells, however, infected <i>D. discoideum</i> were less sensitive to ethidium bromide toxicity, suggesting that <i>Paraburkholderia</i> may also have a protective effect on its host. By contrast, <i>D. discoideum</i> infected by <i>Paraburkholderia</i> did not show differences in their sensitivity to two non-symbiotic pathogens. Our results expand previous work on yet another aspect of the complicated relationship between <i>D. discoideum</i> and <i>Paraburkholderia</i>, which has considerable potential as a model for the study of symbiosis.