Paraburkholderia bonniea symbiont strain identity impacts amoeba host fitness and rate of horizontal transmission.

strains varied in their ability to proliferate within groups of hosts and in the degree of fitness loss they caused given a similar infection prevalence. More importantly, variation in the latter property, known as benevolence, led to increased horizontal transmission of benevolent strains compared to malevolent strains during the social stage of the host life cycle.