Many of the bacteria in this group are involved with eukaryotic hosts. An example would be the Rhizobium. It is a species that live in nodules within the roots of plants in the bean/pea family. From here the bacteria can convert nitrogen to compounds that the host plant can use to make proteins. Species in the genus Agrobacterium produce tumors in plants. Genetic engineers use these bacteria to carry foreign DNA into the genome. Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis.